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Quincy

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  1. Quincy
    Here is a snowfall map that I created using reports from various sources. Many of the reports came from this forum and the National Weather Service. Only social media reports that passed through quality control were considered. All reports gathered were carefully considered and compared before being included.
    Light rain developed during the morning hours on November 26th and mixed with some sleet inland. Wet snow initially confined to the far northwestern corner of the state. As steadier precipitation moved in, a slight southeast shift of the snow/sleet line was observed with some modest evaporational cooling. However, much of coastal and southeastern Connecticut stayed predominantly rain.
    The main reason for the mixed precipitation and sleet was a warm layer in the atmosphere around 700mb. As precipitation became heavy, sleet fell across much of central Connecticut. Wet snow continued across northwestern Connecticut and rain moved as far northwest as Meriden and Hartford with some warming aloft nudging into the valleys. Even in those areas, the 2-meter temperature hovered around 34 degrees for much of the event, which did not allow for significant amounts of snow to accumulate.
    Precipitation tapered off to scattered snow showers by early evening. As cooler air gradually funneled in, a light additional accumulation of snow was reported in many areas. A few broken, but locally enhanced bands of snow continued into the early morning hours on the 27th.
    The greatest snowfall totals were in the range of 6 to 10 inches across northwestern Connecticut. Totals dropped off fairly quickly to the south and east. A narrow area of 3 to 6 inches was observed near and just northwest of I-84. Just southeast of there, 1 to 3 inches was reported and the southeastern third of the state generally saw less than one inch of snow. Where the snow did accumulate, it had a very high water content, especially those areas that battled between a mixture of snow, sleet and rain.

  2. Quincy
    There have been no major changes to the previous forecast. Some of the snowfall totals have been trimmed back ever so slightly. A fairly widespread area of 5 to 10 inches of snow is expected, with a jackpot across much of interior Massachusetts, where most or all of the precipitation should fall as snow.
    Snow becomes heavy at times early Monday morning and begins to mix with sleet and freezing rain by the morning rush around New York City. The mixing then spreads into southern New England by mid morning. After a few hours of sleet and freezing rain across the coastal plain of Connecticut, precipitation should quickly begin to lighten up by late morning to midday.
    Across northeastern Massachusetts, snow will continue through early afternoon before tapering off by early evening and as a result, around a foot of snow is forecast here. The greatest threat for icing extends from northern New Jersey into the lower Hudson Valley and portions of southern and central Connecticut.

  3. Quincy
    Thanks to some feedback, I cleaned up this map and added a few additional reports.
    There are still some gaps in Litchfield County, a report of 4.0 inches in Torrington made more sense based off of observations and radar imagery for that area. You can see how the higher amounts were generally confined to the higher terrain, with lower amounts in the Conn. River and Shetucket River valleys.
    Below is a color, contoured map I put together:

  4. Quincy
    I don't really expect much snowfall at all tonight. For some continuity and a slight amount of uncertainty, I painted the entire area with 2" or less of snow. Eastern Conn. and northern R.I. have perhaps a 50/50 shot at 1-2": of snow, while the rest of the area has a high probability of receiving less than 1".
    Temperatures and moisture look very marginal and although some precipitation should back southern sections of southern New England, I don't see it being a big deal. There may be a few slushy roads for the Thursday morning commute.
    I don't think it's fair to make a total snowfall map for both events. The coastal plain should rise several degrees above freezing during the day on Thursday with most inland areas also cracking 32F. Also, western areas that may see no accumulation at all tonight could easily end up with some of the higher amounts tomorrow night.

    The snow Thursday night into Friday morning ("Round 2") looks a bit more significant. It gets tricky nailing down enhanced snow along an inverted trough across eastern N.Y. and western New England. At the same time, precipitation closer to a center of low pressure well south of Cape Cod may bring a period of snow to northeastern Conn., northern R.I. and interior eastern Mass. Here, it's a big question mark where totals could verify either low or high. The computer models are having issues nailing down precipitation totals, while some say widespread amounts over 6" could be realized in my eastern 3-6" zone. I don't see it happening, but take that for what it's worth.
    The confidence for the latter forecast is only moderate, but this will be my last snowfall map for the period. Confidence is higher for the first round.
  5. Quincy
    Here is a final snowfall forecast for the upper mid-Atlantic region and southern New England for the Blizzard of 2015. No major changes were made to the forecast, but the western fringe was trimmed somewhat.
    It's becoming a nowcast situation, as the computer models are relatively all over the place. The 12z Euro is one extreme (heavy west), with the 00z RGEM further east and much less impressive. Based on radar trends, the previous forecast map and a consideration to the model consensus, here is the latest thinking:
    The shield of heavy snow is backing west through Long Island and southern New England as of 11:35 p.m. Monday. The back edge should make it to roughly the New York border before it essentially stalls. Interior southern New England should remain within the steadiest snow for the longest period of time. There are still unclear details about a mesoscale band of enhanced snowfall totals, but a general 20 to 26 inch snowfall is expected from the hills of eastern Connecticut into much of interior eastern Massachusetts. Banding may result in some 30"+ snowfall amounts, somewhere between northeastern Connecticut and the Worcester-Boston area.

  6. Quincy
    A notable threat of severe thunderstorm activity in early February has been showing up in the models for several days now. As the event gets closer, confidence is increasing that a setup favorable for severe weather is likely to occur. However, there still are a lot of details left to be nailed down. The broad pattern involves a vigorous trough in the jet stream digging across the Four Corners region on Monday, February 1st and swinging east to northeast across the United States into Groundhog Day. The greatest severe weather threat will be focused on where energy around this trough ejects with the orientation (tilt) of the trough being a factor of important consideration.
     
    Lee-side cyclogenesis is likely on Monday across the southern High Plains with low pressure rotating from the Texas/Oklahoma vicinity into the Middle Mississippi Valley and eventually the Great Lakes. Given the low-level jet projected with this system, ample moisture return should bring 60+ degree dew-points northward into the Gulf Coast states. Instability forecasts have varied from weak to modest and the shear signal has been significant, with a sizable area of 50+ knots of 0-6km shear likely.
     
    Similar setups in the past (analogs) have mixed signals, with some showing significant severe outbreaks and others with little to no severe activity. My main focus at this point is the orientation of the trough. A more negatively tilted trough will yield an increasingly unidirectional wind field. If the trough is closer to a neutral tilt or slightly positive, that would maximize the amount of directional shear. The trends appeared to favor the trough becoming negatively tilted on Tuesday, February 2nd, meaning that the storm mode could get messy and trend toward a squall line. The new 00z ECMWF shows a trough closer to a neutral tilt as the upper level flow is southwesterly, not south-southwesterly. If this were to be a hiccup and the trough is more negatively tilted, then the severe threat will not be maximized. It is important to note that severe thunderstorms, including tornadoes, will still be possible in this scenario, but if the ECMWF is correct, we may have a more significant threat to monitor.
     
    Based on the latest data, I would expect an isolated, conditional severe threat to develop across the southern Plains late Monday into the overnight, mainly from parts of North Texas into the eastern half of Oklahoma. Given cold advection and steep mid-level lapse rates, the major threat would likely be large hail, although damaging winds and perhaps a couple of tornadoes would also be possible. Tuesday is the day of focus, as any discrete to semi-discrete thunderstorms that develop in the warm sector could become tornadic. It appears that this area will encompass northeastern Louisiana and eastern Arkansas into Mississippi, far southeastern Missouri, far southwestern Kentucky and western to middle Tennessee. Although the threat could punch north into southern Illinois, southern Indiana and more of Kentucky, meager instability amidst an increasingly pinched warm sector, there is lower confidence in this scenario. Also, the severe threat could reach Alabama later in the day, but the last several runs of the ECMWF have suggested a somewhat slower evolution, keeping the threat a bit farther west, perhaps only reaching northwestern Alabama.
     
    With all of this said, severe weather seems likely on Tuesday with at least a few tornadoes. The wind fields would support a strong tornado. If one or a combination of the following conditions are met, then this setup could turn into a higher-impact event with numerous tornadoes, some strong and long-tracking: More instability than currently forecast would support a more robust setup, particularly in terms of localized vs. larger scale. A near-neutral or even slightly positive tilted trough would increase the amount of directional shear. Discrete thunderstorm development in the warm sector, especially early in the day on Tuesday, would suggest an elevated tornado threat.
     
    First thoughts:
     
    -Conditional threat of a tornado or two late Monday night/early Tuesday.
    -At least a few tornadoes on Tuesday; better than 50/50 odds of a strong tornado.
    -Tornado threat is maximized on Tuesday from far northeastern Louisiana and eastern Arkansas into northern Mississippi, western to middle Tennessee, far southeastern Missouri, far southwestern Kentucky and northwestern Alabama.

  7. Quincy
    Recapping May: On the heels of a relatively active month for severe weather and tornadoes in April, May 2015 continued the pace. Although the month started slow with no tornadoes for the first two days and only a handful through the 5th, the greatest single day tornado event of 2015 occurred on May 6th. This was actually expected to be proceeded by a much more significant event on the 9th, but the former won out with 59 tornado reports, as the 9th did not fully live up to the hype/potential*.
    The first third of May paced at a somewhat above average count of tornadoes. Steady tornado events continued fairly regularly through the middle and latter portion of the month. Although there was no “defining” tornado outbreak after May 10th, there were multiple instances of picturesque tornadoes. While the previous forecast for May hinged on a near-average month, it looks like the period will end up at least slightly above average. The analog May of 1991 turned out to be the best fit among the four analogs from the 1990s. It was also the most active one of those four. The very persistent troughing across the Inter-mountain West to High Plains was well-indicated in both the forecast ensembles and analog data. Long-range forecasts may not always work out that well, but in this case, the verification speaks for itself. Only four days in the month reported no tornadoes, 5/1, 5/2, 5/12 and 5/31**, which includes an 18-day streak of reported tornadoes from the 13th to 30th.

    To quickly touch on the Plains long-term drought, it has been reduced significantly. Consistent bouts of heavy rain and convective activity have eliminated most of the drought area in the central to southern Plains. It now covers just a fraction of an area that it had before. In terms of tornado activity, the moisture transport northward has boosted the storm potential, but in a way, has also hampered the ability to easily storm chase. Without much EML (elevated mixed layer) influence this May and a tendency for storms to congeal into MCSs (mesoscale convective systems), countless tornadoes have been produced by high-precipitation supercells. Many of those tornadoes were rain-wrapped and/or difficult to see. Portions of Oklahoma reported a record-breaking 20 inches of more of rainfall in the month of May this year. A large portion of the southern Plains came in with precipitation anomalies of +8 inches or more for the month. That essentially means an extra two to three months worth of rain fell, if not more. This has caused major flooding in much of the region.
    June 1st through 10th: A general continuation of the recent pattern should continue through at least the first week of June. While the month begins with ridging across the southern Plains, the short-range models and global models alike are in strong forecast agreement with the upper level pattern. A trough is progged to dig into the West Coast with ripples of shortwave energy swinging into the central/northern Plains from June 1-3. Even though neither one of those three days appears particularly significant in terms of tornado potential, multiple severe reports, including tornadoes, should occur each day. After that, the parent trough is expected to continue digging and beyond that is where the forecast gets a little bit tricky. When looking back at the ensemble forecasts, the models had a ridge bias and did not really pick up on the trough becoming as amplified as it may. (For example, the most recent run, May 28th, of the Euro Weeklies looks much different for the second half of the first week of June, in comparison to the May 31st Euro ensemble run, which is more amplified) The trough could also become cutoff as some model projections indicate. The current expectation is that the trough axis may be just a little bit too far west to favor an outbreak-type severe setup in the Plains. With that said, whether the trough eventually ejects east to cause a significant event, or rather just a string of steady days (much like April and May of this year), there should be fairly consistent tornado threats through about the 7th or 8th of June. Rounding out the period, whatever is left of negative height anomalies in the West should relax to near climatology.
    Verdict: Somewhat above average tornado activity between June 1st and 10th. Fairly consistent bouts of severe weather, including tornadoes, are expected through the first week of June. Much like the previous six to eight weeks, while there may not be a higher-end severe setup on any particular day, tornado reports should be observed on most of these days.
    June 11th through 30th: Fighting with climatology and the computer model forecasts, there is only so long that relatively amplified troughing can dominate the pattern across the western half of the U.S. Starting with analog guidance, the results are fairly mixed. The general pattern assessed in the top four analogs (based off of GEFS 8-14 day prog from 00z 5/31 and extending out 20 days) is characterized as featuring ridging across the western U.S. to central/southern Plains and some troughing across the Great Lakes. It sounds a bit like what happened to start 2015. However, the individual four analogs (based on early June 2015 forecasts) diverge greatly in the period 10 to 20 days following. The 1991 analog, which was a strong match to May 2015, continues to show up. That June featured slightly below average tornado counts. Another analog that was also mentioned in the May 2015 tornado forecast is 1990. This one also shows up for the month of June and that particular month was well above average in terms of tornadoes. On the flip side, the other two analogs showed well below average tornado counts. The expected pattern to start June 2015 resembles late June 2006. That June finished fairly quiet and was followed up by one of the quietest months of July on record in terms of tornado activity. The final GEFS-based analog is 2002. That June was even quieter than 2006 and July of that year was also well below average for tornadoes.

    What can be made out of these mixed signals? Based on persistence and trends observed so far this spring, the computer forecast models have generally erred on the side of too much ridging occurring too quickly in a long-range forecast. It is inevitable that ridging will eventually prevail, but that does not entirely shut off the tornado season. In fact, it is very possible, if not probable, that troughing across the Great Lakes and/or Northeast could enhance the threat of severe weather from the Midwest into the Ohio Valley. A northwest flow regime tends to favor tornadoes in that region, especially the Ohio Valley. The expectation with this forecast is that mid-June should feature decent tornado potential, but that late June may not be as active. All four of the analogs above were eventually followed by a sharp drop-off in the tornado season, whether that came in late June or July. Also, one cannot forget June 16-18, 2014, in which an otherwise quiet tornado season become extremely active seemingly out of nowhere.

    Moisture return cannot be overlooked and this sets June 2015 apart from recent months of June. The soil moisture content across much of the Plains is much higher than it has been in at least two to three years. The period from May 1-29, 2015 featured slightly to somewhat above average soil moisture content from the Southwest into most of the Plains. This available moisture alone would tend to favor tornadoes, even if upper air and kinematic support are marginal. If the jet stream can stay active and provide enhanced flow aloft, a setup like mid-June 2014 could be possible sometime in June 2015. If such a setup did occur, available moisture would probably not be a concern at all. The bigger question becomes, can the Plains and Midwest eventually see more EML influence? That may be the difference between another “climo month,” versus a more memorable month for tornadoes.
    So far in 2015, it has been an active tornado season in two areas. One lies from north Texas/Red River Valley into central Oklahoma. The other is across the central to southern High Plains. Looking ahead to June 2015, early June features tornado prospects from the central/northern High Plains eastward into the Dakotas and Nebraska. Later in June, signs point toward Siouxland eastward through the Midwest and into portions of the lower Great Lakes/Ohio Valley.
    Verdict: Near to slightly average tornado activity between June 11th and 30th.

    June 1-10 forecast: Somewhat above average tornado counts in the U.S.
    June 11-20 forecast: Near average tornado counts in the U.S.
    June 21-30 forecast: Slightly below average tornado counts in the U.S.

    June 2015 tornado estimate: 255 tornadoes in the U.S. (slightly above average)
    *As has been the case many times this year, morning convective activity and MCS dominance have mitigated the frequency of discrete supercells.
    **This is subject to change as it may take a day or two for official reports to come in for May 31st.
  8. Quincy
    There is the potential for a regional severe weather event on June 22nd. The threat zone extends from portions of the middle/upper Mississippi Valley into the western Great Lakes. All severe weather hazards are possible and given the nature of the setup, forecast trends are being closely monitored.
    As at least two pieces of shortwave energy rotate from the upper Midwest into the Great Lakes on Monday, a surface low is forecast to deepen from Iowa/Minnesota into Wisconsin. Impressive wind fields for this time of the year will combine with strong instability to create an environment favorable for severe weather. As it stands right now, two rounds of storms are expected. The first round would most likely be in the form of a mesoscale convective system (MCS) Monday morning, moving into the Great Lakes by midday and early afternoon. The second round develops in the wake of this activity, at and shortly after peak heating, later in the afternoon.
    The setup is a bit complicated and there are reasons to believe that two rounds of mixed intensity are favored over one robust atmospheric punch. The MCS during the first half of the day could pose a threat for primarily damaging winds and isolated hail. Once that system moves out, there should be modest air-mass recovery. The issue is that wind fields in the lower levels begin to veer, causing a more unidirectional shear pattern. This will likely dampen the tornado potential somewhat. Nonetheless, even forecasts on the more conservative end of the spectrum indicate a setup favorable for at least a few tornadoes. The afternoon to early evening threat may feature fairly widespread damaging winds, if storms were to merge into a linear system. Supercells still appear probable and they may extend into the early evening. However, for the reasons listed above, this does not look like an ideal setup for a major severe weather outbreak.
    Trends for this event tend to move the surface low a bit quicker, which also speeds up the veering of winds. The best wind fields may also become somewhat displaced to the northeast of stronger instability to the south. The Euro has joined the GFS/NAM in developing strong instability, as earlier it was showing a less unstable setup. The RGEM is also on-board and all of the models are in general agreement in terms of timing and geographic placement.
    Wisconsin is the target for the initial MCS on Monday. That system should weaken as it moves into portions of upper and lower Michigan. Later in the day, the target becomes southern Wisconsin and northern Illinois. Portions of lower Michigan and northwestern Indiana may also get in on some action. Damaging winds should be the predominant threat. The stronger cores can produce large hail and a few tornadoes seem probable.
    At least one of the following scenarios would need to occur to more fully maximize the tornado threat: First, outflow from the morning MCS could work to set up one or more boundaries to locally enhance a tornado threat. If the MCS decays faster than projected, that could lead to less disruption of the wind field and even stronger instability. A mesoscale low and/or a main low tracking further south into southern Wisconsin (instead of northern sections) may maintain more backing in the lower level wind fields through the threat zone.
    It should be noted that even with the projected wind fields, at least a few tornadoes remain likely. Given both a strong low level jet and 0-6km shear in excess of 50 knots, there is at least some potential for strong tornadoes. All of the factors currently forecast likely place Monday into more of a mid-range (SPC moderate risk) severe weather threat, as opposed to a higher-end (SPC high risk) outbreak. Stay tuned to later forecasts to see how the forecast setup evolves.
    The NAM forecast below for 21z Monday shows winds veering substantially across Wisconsin and Illinois:

  9. Quincy
    The April tornado forecast was a trial run and a lot has been learned since it was made. After some success with that forecast, I will be incorporating a lot more statistical analysis (analog data) into coming up with a forecast for the month of May.
    Quickly recapping April:
    Overall, April was a fairly steady month for tornado reports across the U.S., with 21 out of 30 days reporting tornadoes. April 1-9 was very active, including a notable, early season EF-4 tornado in northern Illinois. April 10-18 was relatively inactive, but had tornadoes reported in all but two of those days. April 19-27 was rather active, but no single day featured a major or significant outbreak. Most of the tornadoes in the month were EF-1 or weaker, although the April 9th EF-4 was an exception. Preliminary tornado counts indicate that the month was near to slightly below average in tornado activity. The prior forecast issued on March 31st predicted slightly above average tornado counts. Once the numbers become official, I will get into more detail with comparing the forecast vs. actual.
    Before we get into May, there are some things to consider with the current state of the U.S. Although a long-term drought continues for much of the Plains, heavy rainfall throughout April reduced drought conditions considerably across portions of Oklahoma and Texas. This is critical, because relative tornado inactivity during the first half of spring 2014 across the Plains was at least partially attributed to a lack of available moisture. When we think about creating environments that support tornadoes, moisture is key and that moisture source can originate in Texas. Yes, the Gulf of Mexico is another player, but that moisture must also be able to track hundreds of miles inland, across the big state of Texas.
    Additionally, the overall atmospheric pattern has shifted somewhat, as although there has been continued troughiness across eastern Canada and the Northeast, we are seeing a trend toward more ridging developing. This will have many implications on how the tornado season evolves into May. With less blocking across northeast Canada toward the North Pole, that should tend to favor positive height tendencies as well. (Not to mention seasonality helps with that as well)
    For this outlook, the focus will be split into two portions. May 1-10 and May 11-31. I will still include breaking the month down into thirds at the end of the outlook, but keep in mind that specifics beyond May 10th lack the confidence needed to get into extreme detail in that time period. May is also a potentially volatile month, as one outbreak or even one day for tornadoes can effectively skew the big picture. It would be difficult to nearly impossible to predict any such outbreak more than 10 days in advance. The point of this outlook is to look at May as a whole.
    May 1st through 10th:
    After a quiet finish to the tornado season in April, the first few days of May look to continue that theme. This should not last long, though, as both the operational and ensemble forecast models are in strong agreement with the expected pattern. On paper, it looks encouraging for severe weather prospects. An upper level trough and surface low should exit the New England area may May 3rd, leaving the Lower 48 with a relatively zonal pattern, at least for a short-time. Downstream ridging across the East should give way to a digging trough across the West Coast by May 4th to 5th. With some blocking across eastern Canada, we are looking at western U.S. trough that will persist for several days, with potentially multiple impulses rotating around from the Intermountain West into the Plains.
    This could ultimately evolve in many ways. At this point, the most probable scenario would appear to be two to three, perhaps four, days that are conducive for minor to moderate severe weather events, including tornadoes. I would not want to write off the potential for a big event just yet, but it seems more likely that we will have a series of smaller events, kind of how April panned out. What will be working in the favor of severe weather will be the bonus of a better moisture source across the southern Plains and moderate to strong instability ahead of approaching shortwaves. It is the details that get somewhat muddled out, with the amount of clearing/destablization, storm mode, locally backed winds, etc. Essentially, the pattern looks favorable for severe weather and tornadoes, particularly between May 5th and 8th. As mentioned before, maybe only two of those days wind up decent for severe, but if the pattern lines up just right, there could be multiple tornadoes each day.
    Verdict: Near average tornado activity between May 1st and 10th. The period should begin quiet, but then see multiple days with at least modest tornado activity. The period may close out with a couple of quiet days as the pattern trends more zonal, assuming the model projections are correct.
    May 11st through 31st:
    I have put a lot of time into assessing analog data for this period and not so heavily relying upon forecast model ensembles, as was the case with the April tornado outlook. What has been most alarming lately is that the longer-range models have really struggled beyond day 10 over the past several weeks and have often showed little to no skill in the period of days 15 to 30. This means that the models have flip-flopped back and forth, giving little meaningful insight to what might lie ahead. Now, I am not totally discounting the models here. Sometimes they can struggle during a large scale pattern change, much like what we may be seeing into May. I put a fair amount of stock into the European ensembles/weeklies, but I think taking a look at the past will help shed some light on what might happen in the future.
    To come up with analogs, I have looked at two things in particular. First, I assessed the short-term model analogs for May 1-2. Secondly, I looked at the day 6-10 ensemble predictions from the GEFS and those analogs. There was some overlap and plenty of similarities to note. In the broad scheme, the analogs began with the western troughing/eastern ridging that we are expecting to see into the first week of May. The analogs are then in strong agreement with positive height anomalies along and east of the Rockies from the 2nd week of May, pretty much through the entire month. After gaining visibility to the latest 00/30 Euro Weeklies, pretty much the same is the case here. That only increases confidence in this forecast. I pretty much disregarded the CFS entirely for this outlook, as its members are all over the place for May and as an ensemble system, has not had a good track record as of late.
    Going back to the ridge axis, that is the key thing to consider. The indications, in general, point toward a mean ridge axis setting up somewhere between the Missouri River and the Mississippi River. The latter, or a further east ridge axis, would be more supportive of tornadoes, allowing for troughs to dig a bit further south and west into the Plains. Even the former would be encouraging, as it would tend to favor High Plains activity. That region has not had a great chase season in a while. Based on the reports, it appears as if 2010 was the last solid year there and 2008 was decent too, particularly across western Kansas. Either way, since we are looking at a broad period here and kind of splitting hairs, there is nothing necessarily stopping from a rogue, deep trough to swing through, although it would appear that if that was going to happen, it would tend to favor late May over mid-May. As a result, I am leaning toward a somewhat more active end to May, even though I do expect a fair amount of activity in the middle of the month as well. (When I say fair amount of activity, I expect several days with scattered severe reports, again, in some ways similar to what April featured)
    Verdict: Near average tornado activity between May 11th and 31st. The middle of May holds some potential, but is forecast to feature slightly below average tornado reports. Into late May, there are some indications that tornado activity could rebound to near to slightly above average levels with more potential activity.
    When looking at some of the recent analogs (over the past 25 years), 3 out of 4 had slightly to moderately below average tornado counts in May. On the flip side, they tended to favor average to even very active months of June. Since May 2015 does not appear to be a particularly close match to any of those analogs, I would take that information with a grain of salt. If anything, it does give at least some additional confidence in the thinking that May could end more active and lead into another active June. I do not want to get ahead of myself here, so we will hold off on further discussion about June until the next monthly tornado forecast.
    May 1-10 forecast: Near average tornado counts in the U.S.
    May 11-20 forecast: Slightly below average tornado counts in the U.S.
    May 21-31 forecast: Near to slightly above average tornado counts in the U.S.

    May 2015 tornado estimate: 260 tornadoes in the U.S. (near to slightly below average)
    For those wondering, the top 5 analogs are as follows, beginning with the given date and extending out 20 days: 4/28/1994, 5/12/1991, 4/28/1957, 5/10/1993 and 5/18/1977, in that order. The “recent” analogs mentioned earlier in the post were 1990, 1991, 1993 and 1994.
  10. Quincy
    Following up a cold winter across much of the country, April has proven to be a transition month. Although the month started mild for a large portion of the country, much cooler air has moved in for the middle of the month. There are signs, however, that any negative temperature departures after April 20th into the start of May will be relatively insignificant.
    Before looking at May, it makes sense to look at the April forecast. For the most part, everything is going to plan from the forecast that was made on March 15th. Although portions of the Northeast have been milder than forecast for the month as a whole, one and perhaps two shots of cool air to finish the second half of April will likely counteract the present offsets. As far as the models go, the Euro MJO prediction of moving into phase 2 and 3 verified very well, although the MJO has since looped back around into phase 5 an 6.
    Click here for a follow-up to the April forecast.
    Going forward, there continue to be signs of the remnant winter pattern of troughs across the East Coast breaking down. The Euro shows no clear move with the MJO, although it tries to keep it in the vicinity of phases 4-6 to even neutral. Each of those phases would suggest near to slightly above average temperatures for much of the center and eastern portion of the country with slightly below average temperatures across portions of New England. The GFS ensembles move toward phase 8 and 1, suggesting more of a northern Plains warm-up with near to even below average temperatures near the Gulf States.
    With no strong signals with respect to the MJO, focus shifts toward the Euro and CFS. The Euro weeklies show a fairly zonal pattern with only near to slightly above average temperatures for much of the area. Much like the MJO projections, such a pattern could yield near average temperatures across the Gulf States. The CFS is robust with warming across the upper Plains and yields near to slightly above average temperatures for most other areas. While the CFS keeps the upper Great Lakes below average, this may be overdone due to below average water temperatures.
    Final considerations and forecast:
    The thinking is that the persistant drought across the desert Southwest and adjacent lower Plains will continue. This will especially be the case if the CFS is correct with pronounced ridging in the area. The dry soil will tend to favor above average daytime temperatures. So while there may only be substantial confidence in slightly above average temperatures in the range of 1 to 2F across the mid-Mississippi and Ohio Valleys, a +2 to +3F anomaly forecast has been introduced for portions of the western lower Plains. Ridging could extend into the Great Lakes, but still below average water temperatures should mitigate any warming, especially downwind of a prevailing west-southwest flow. There is moderate confidence in some cooler than average temperatures hanging on across northeast New England, so a small area of -1 to -2F anomalies are included for Maine.
    Severe thunderstorms:
    A forecast graphic is not being made for this outlook with respect to severe thunderstorms. The year 2014 continues to follow a near-record low number of severe thunderstorm events and tornadoes. A series of severe weather events, which may or may not be significant, are possible between April 23rd and 25th. Beyond that, a fairly zonal flow with some above average heights in the Plains and Midwest does not look overly impressive for severe activity. However, the pattern will favor at least an increase to near average activity through the month of May. In summary, the severe thunderstorm forecast is close to climatology and has little confidence in specifics. Prior years that saw very low activity through mid-April did see an increase in activity by late April. A close analog to 2014 is 2010. That season saw an uptick in severe reports between the end of April and through the month of May.

  11. Quincy
    There was a lot of anticipation leading up to July 15th. Some argued there was a "very impressive" severe setup unfolding for (southern) New England, but there was plenty of disagreement with the placement and potential severity of such an event.
    For a quick summary, the severe weather parameters in place (both forecast prior and during) the event were marginal compared to past severe events in southern New England. Not one important severe weather parameter was terribly impressive and there were many pieces to the puzzle that were missing here.
    As of July 17th, there have only been a handful of severe wind reports, centered over a small geographical area between far northeastern Massachusetts and adjacent far southeastern New Hampshire. There were a few damaging wind reports in downeast Maine, along with two marginally severe hail reports. Although there were several tornado warnings in the area, only one tornado has been confirmed so far. That was an EF-1 in Somerset County, Maine. (this blog post will be edited if any additional tornadoes are confirmed) Flooding was more of a widespread issue across much of New England and extending down into the NYC metropolitan area and New Jersey.
    There are some misconceptions as to what constitutes as a “significant” or “impressive” severe setup in New England. Generally almost all significant severe outbreaks occur with a west to northwest flow aloft and an anomalously strong overlap of shear (speed and directional) and instability. While it’s not uncommon to see strong instability and significant wind shear in this part of the country, they don’t often coincide with each other. There are other setups too, which are usually more marginal, sporadic and difficult to forecast. While some southwest to southerly flow events have produced severe, unless key ingredients are in place, those events usually only result in widely scattered or isolated severe reports.
    This event was well-modeled in the synoptic view. There was an anomalously strong upper level cutoff low moving into the Great Lakes. Ahead of this feature, there was a surface cold front advancing through Pennsylvania and New York with a pre-frontal/lee-side surface trough axis across New England by the morning of July 15th.
    While this may sound like a good setup, as often is the case in this part of the country, many additional things have to line up just right. If one or two (or more) variables don’t pan out right, then the whole setup will likely underperform compared to expectations. Timing was also another issue, as with the cutoff low displaced so far west from New England, the best forcing would also remain further west.
    The mesoscale models were predicting anywhere from 500 to 1,250 J/kg of MLCAPE (with somewhat greater SBCAPE) coinciding with 30-40 knots of bulk shear across central New England and portions of western southern New England. While both parameters are what can be considered “elevated,” they are on the low end (lower 50 percentile) for what has been observed in the Northeast in prior tornado cases. When looking at severe producing supercells in general (all types/modes), the values mentioned above are actually even less significant. Consider that the mean bulk shear value for supercells in the southwestern New England window* is 44 knots with a mean MLCAPE value of 1,421 J/kg.
    So, there were two key parameters in place that were elevated, but not terribly impressive in comparison to past severe events. There is another piece here that made the whole setup look even more marginal. Storm relative helicity or SRH (effective) was very meager on the computer forecast models for July 15th across most of the area. The progs were only between about 50 and 100 m2/s2. This is again on the low end, when considering that the mean SRH value for tornado and supercell cases alike in the area is 139 m2/s2 (which some cases over 300 m2/s2).
    While looking at this forecast setup from a strict numerical standpoint, while the threat of tornadoes and other severe weather were somewhat elevated, it was clearly a “below average,” or in other terms, an “unimpressive” setup.
    As far as the model simulated radar guidance, the NAM struggled to develop much in the way of discrete cell activity across southern New England, instead favoring a line of thunderstorms moving in from eastern New York by late afternoon and evening with stronger forcing ahead of the cold front. The HRRR was a bit more alarming, with a line strong to severe cells and clusters moving into southwestern New England by late afternoon. The HRRR by the 11z and 12z runs were showing some weak convection along the pre-frontal trough giving way to stronger convection further west later on.
    The morning of July 15th:
    Convection was already firing along the pre-frontal trough by midday, but due in part to limited heating, and weak forcing, the activity across Connecticut and south-central Massachusetts never reached severe limits. The HRRR continued to show stronger activity later in the day, but later runs gradually backed off on that idea. It was clear from the start that there was also a fairly unidirectional shear pattern with not much backing of low-level winds. Surface observations through the entire event, including the early to mid morning hours, showed surface winds S to SW.
    It cannot be overlooked that a small area from northeastern Massachusetts into southeastern New Hampshire and much of Maine did see scattered strong to severe thunderstorms develop later on during the afternoon.
    Analyzing the severe weather parameters on July 15th:
    The models did a good job of predicting wind shear, as the SPC mesoscale analysis showed an average of about 40 knots of bulk shear across the area, with more across northern and northwestern sections and less across southern and southeastern sections. MLCAPE was also close to model guidance with generally 1,000 J/kg, on average. The pre-frontal activity did decrease instability across Connecticut with a noticeable uptick in CIN, especially in the vicinity of the trough. It was across northeastern Massachusetts and points northwest where less CIN and more significant SBCAPE values supported more in the way of storms being able to reach marginally severe limits.
    Taking a step back, the mid-level lapse rates were fairly unimpressive across the area and this was acknowledged by SPC leading up to the event. The reanalysis showed lapse rates of 5.5 C/km or less across much of southern New England, with some lapse rates over 6 C/km across Maine.
    Upper level considerations:
    Analogs very strongly favored a relatively low-end severe event, especially given the position of the upper level low and the fact that the flow aloft was out of the SW. The RAP analysis from July 15th shows that the most significant vortmax was located very close to the upper level low, which was west of even western New York. There was some positive vorticity advection across northern New England, which likely was a factor in boosting some of the severe thunderstorms north and northwest of Boston, Mass. The mesoanalysis showed a weak, elongated vortmax between 18z on the 15th and 00z on the 16th, but this was up across northern Vermont and the northwestern Maine/Canada border.
    Finally, when also looking at the upper level flow, it was once again below climo levels with respect to significant severe events. The GYX and OKX soundings showed just 40 knots and 39 knots respectively of 500mb flow at 12z on the 15th. The upper level flow actually decreased notably at OKX to 31 knots by 00z on the 16th. While severe events can occur in the Northeast with limited upper level flow, the more impressive events typically have much stronger flow aloft. It should also be mentioned that the 850mb jet was unimpressive, with wind speeds of just 20 to 30 knots. Only one run of the Euro showed a signal of a strong jet and that was 144 hours prior, when it was predicting 45-55+ knots of 850mb flow.
    The relatively weak flow and generally unidirectional shear pattern can be seen clearly in the 12z July 15th OKX sounding:

    Considering the mesoscale models:
    The HRRR performed poorly on the larger scale, as it did not show pre-frontal activity contaminating the environment across southwestern New England. Instead, it was more optimistic in terms of severe and even showed somewhat alarming significant tornado parameter values over 1 across much of Connecticut. Although some convection did cross over from Long Island into Connecticut, this wasn’t until late at night and most of that activity was marginally severe or below severe limits. Some fairly weak storms did fire across eastern New York by late afternoon, but those merged with other convection to form a very messy storm mode, one that favored training of heavy rains and flash flooding. The models also showed more backing of low-level winds than what was observed on the morning of July 15th and through the event.
    In summary, what went wrong?
    While it’s easy to blame the entire bust on early day convection across Connecticut, consider again the forecast parameters in place that verified very closely to the actual analysis. Instability was somewhat elevated, but still modest at best with around 1,000 J/kg of MLCAPE. Shear was also elevated, but 40 knots of bulk shear is somewhat below the average for past severe cases. One of the most glaring parameters missing from the equation was helicity. Helicity was expected and verified to be quite low on the spectrum, with 100 m2/s2 at best, while tornado activity favors more than that. With a SW flow aloft, a more strongly backed low-level wind profile would have supported a greater threat of severe. Instead, any backing was minimal, with the mean low-level wind flow being S to SW. It would have been one thing if mid-level lapse rates were impressive, to offset some of the other marginal parameters, but 5.5 C/km is not going to make up for everything else.
    *
  12. Quincy
    Here's a recap of the 2013 tornado season across the Northeast.
    Connecticut had four reports of tornadoes during 2013, which is roughly twice the average amount of about two. Keep in mind that 2012 had no tornadoes in the state, so one could argue that this was nature's way of balancing itself out.
    Elsewhere, New Jersey was the only other state in the Northeast with above average tornado reports. (They average two per year, but had three in 2013) Maine is not pictured here, but Maine had at least two tornado reports. Since they average two per year, that's right at average. Massachusetts also saw an average year with one tornado report. Vermont and New Hampshire typically average about one tornado per year, but both states saw no tornadoes this year. New York was well below average with just four tornadoes. The average there is 10 per year. Pennsylvania reported nine tornadoes, also well below their average of 16 per year.
    Averages based off of 1991-2010 reports, per NCDC.
    April 19th: An EF-1 tornado touched down near Bainbridge, N.Y. and was on the ground for 3.2 miles. (link)
    May 9th: A weak EF-0 tornado touched down near Stoughton, Mass., but the length of damage was less than 0.5 miles. This was a cold air funnel case and not a "classic" tornado. (link)
    May 28th: There were four tornado reports across northwestern Pennsylvania. Three of the tornadoes were rated EF-1s and one was an EF-0. The longest tracking tornado was an EF-1 that touched down near Edinboro and had a damage path of 18 miles long.
    May 29th: Two tornadoes were reported in eastern New York State. One was a significant, long-track tornado (EF-2). It was on the ground for 17 miles and the damage path was up to 1 mile wide. Another tornado, a weaker EF-1, was reported just to the southwest of that storm. (link)
    June 2nd: Two brief and weak EF-0 tornadoes were reported in Maine.
    June 27th: Two EF-1 tornadoes were reported in central Pennsylvania.
    July 1st: A somewhat unusual morning tornado (EF-1) was reported in extreme northeastern New Jersey. The same storm that was responsible for that tornado resulted in three tornado reports across Connecticut from late morning into early afternoon. The first report was an EF-0 that touched down in Greenwich. The most notable tornado was the second one, which was an EF-1 in the Windsor and Windsor Locks areas. A weak, brief EF-0 tornado was the third report in Enfield. (link)
    July 10th: A brief EF-1 tornado was reported near Moravia, Penn. during the afternoon. Less than an hour later, an intermittent EF-1 tornado was reported in Connecticut between Andover and Mansfield. The damage path of that tornado was 11.2 miles long.
    July 27th: An EF-1 tornado was reported in north-central Pennsylvania near Borie. That same storm dropped another EF-1 tornado in adjacent New York State about an hour later. The second of those two tornadoes was on the ground for 14 miles.
    August 7th: A minor EF-0 tornado was reported in southwestern Pennsylvania near Ralphton.
    August 13th: A weak EF-0 tornado was reported near Manahawkin, N.J.
    October 7th: An EF-1 tornado was reported near Paramus, N.J.
    The tornadoes pictured above across Delaware, Maryland and Ohio were not included in the above time-line.
    As might be expected, the strongest and longest-tracking tornadoes across the Northeast this year were across New York and northwestern Pennsylvania.

    Those areas are climatologically favored for significant tornadoes, at least when compared to areas further east. With that said, there have certainly been cases of strong tornadoes in southern New England. The most recent case was the deadly EF-3 tornado that tracked across south-central Massachusetts on June 1st of 2011. The above image is a composite that is not perfectly to scale.
    United States tornado seasons:
    Through then winter, the Gulf States are favored for tornado development. There was a minor event this past Sunday, on January 12th, that featured a few EF-0 tornado reports in extreme southeastern Virginia. Into spring, the focus shifts toward the Midwest and late spring into early summer is when the Northeast most commonly sees tornadoes.

  13. Quincy
    The image is comprised of snowfall totals from various sources, some of which include the New England forum on here. Snowfall totals across Connecticut were pretty uniform around 3-4", although slightly lower amounts occurred along I-95 and there were a few isolated amounts around 5".
    I'll post a contoured color map within the next 12 to 18 hours.
  14. Quincy
    The National Weather Service (NWS) reported that an EF-0 tornado touched down in eastern Massachusetts Thursday afternoon, shortly after 4:30 p.m.
    An upper level low lifted northward through New England on Thursday. An unseasonably cold air mass was in place, resulting in cold temperatures aloft. It was the combination of low Lifted Condensation Levels (LCL's) and moderate wind shear aloft that helped create an environment that was marginally supportive of tornado development. It is possible that a land-sea interaction with winds off of the nearby ocean may have played a role in spawning this tornado. The NWS reported that it was a case of a cold air funnel.
    The tornado touched down in Stoughton, M.A. in Norfolk County and stayed on the ground for 0.25 miles. The tornado was a strong EF-0 with maximum sustained winds of 85 MPH. Damage was minimal, but a local car dealership reported seeing the tornado and had some vehicles blown around by the winds.
    Looking back at historical tornadoes in the Northeastern United States, the helicity values and amounts of instability in place on Thursday were relatively low compared to prior tornadic events. However, it was the low LCL heights and moderate wind shear that did elevate the tornado potential somewhat. On a scale of 0-5, 0 being unfavorable and 5 being highly favorable for tornadoes (based on local climatology), the environment yielded a value of 1.9.
    A note that a 2.5 value would be equal to the mean of past tornadoes.
    PUBLIC INFORMATION STATEMENT
    NATIONAL WEATHER SERVICE TAUNTON MA
    158 PM EDT FRI MAY 10 2013
    ..TORNADO CONFIRMED IN STOUGHTON IN NORFOLK COUNTY MA
    LOCATION...
    STOUGHTON IN NORFOLK COUNTY MA
    DATE...MAY 9 2013
    ESTIMATED TIME...431 PM EDT
    MAXIMUM EF-SCALE RATING...EF0
    ESTIMATED MAXIMUM WIND SPEED...85 MPH
    MAXIMUM PATH WIDTH...50 YARDS
    PATH LENGTH...0.25 MILES
    BEGINNING LAT/LON...42.10N / 71.10W
    ENDING LAT/LON...42.10N / 71.10W
    * FATALITIES...0
    * INJURIES...0
    * THE INFORMATION IN THIS STATEMENT IS PRELIMINARY AND SUBJECT TO CHANGE PENDING FINAL REVIEW OF THE EVENT(S) AND PUBLICATION IN
    NWS STORM DATA.
    ..SUMMARY
    THE NATIONAL WEATHER SERVICE IN TAUNTON MA HAS CONFIRMED A BRIEF TORNADO TOUCHDOWN IN STOUGHTON MA ON MAY 9 2013.
    THE TORNADO TOUCHED DOWN AT A CAR DEALERSHIP ON ROUTE 138 WHERE IT WAS CAPTURED BY A SECURITY CAMERA AND RECORDED ON CELL PHONE CAMERAS BY SEVERAL OF THE DEALERSHIP EMPLOYEES.
    THREE RV TRAILERS...WEIGHING ABOUT 5000 POUNDS EACH...WERE PUSHED BACK ABOUT 6 FEET AGAINST A CHAIN LINK FENCE. ONE TRAILER WAS LIFTED ABOUT 15 FEET INTO A LIGHT POLE BUT LANDED ON ITS WHEELS WITH MINIMAL DAMAGE.
    AN ALUMINUM DOOR ABOUT 20 FEET HIGH AND 15 FEET WIDE WAS BLOWN OUT OF THE SERVICE GARAGE. EYEWITNESSES REPORTED CEILING TILES BEING LIFTED INSIDE THE DEALERSHIP AS THE TORNADO PASSED OVERHEAD.
    THE TORNADO ENTERED A WOODED AREA JUST TO THE NORTHEAST OF THE DEALERSHIP. ABOUT 0.25 MILES AWAY...TWO LARGE PINE TREES WERE DOWNED ON ERICA DRIVE AND DEAN ROAD BEFORE IT DISSIPATED.
    BASED UPON A SURVEY OF THE DAMAGE...THE TORNADO IS CLASSIFIED AS EF0 ON THE ENHANCED FUJITA SCALE WITH MAXIMUM WINDS OF 85 MPH. THE PATH LENGTH WAS 0.25 MILES AND THE MAXIMUM WIDTH WAS ABOUT 50 YARDS.
    Here's a look at radar imagery about a half hour before the time of the tornado:

    The Supercell Composite Parameter was relatively low, although some slightly higher values did target the area near the tornado touchdown:

    The only severe weather report in the Northeast on Thursday was that tornado in Massachusetts!
  15. Quincy
    The National Weather Service (NWS) confirmed that an EF-1 tornado touched down in New York state Friday evening, shortly before 8 p.m.
    A strong cold front moved across Pennsylvania and New York state late Friday evening. At the same time, a marginally unstable air-mass was in place closer to the surface. With moderate to strong wind shear in place and significant storm relative helicity in place, the stage was set for damaging winds and even a marginal tornado threat.
    As a result, a Tornado Watch for a large portion of Pennsylvania and New York state. A tornado touched down near Bainbridge, N.Y. in Chenango County and stayed on the ground for 3.2 miles. The tornado was a strong EF-1 with maximum sustained winds of 110 MPH.
    Looking back at historical tornado environments in the same general area, the wind shear and helicity values in place on Friday were actually more "severe" than the climatological mean for past tornadoes. The only thing that was lacking was instability, as there was very little in place. Despite this fact, strong, twisting and turning winds aloft combined with an approaching squall line ahead of a cold front resulted in the tornado.
    PUBLIC INFORMATION STATEMENT...UPDATED
    NATIONAL WEATHER SERVICE BINGHAMTON, NY
    954 AM EDT MON APR 22 2013
    ...TORNADO CONFIRMED FROM 4 SSE BAINBRIDGE IN CHENANGO COUNTY TO 3 S SIDNEY IN DELAWARE COUNTY NEW YORK...
    UPDATED DATA ON LAT/LON POINTS AND WIDTH.
    LOCATION...
    FROM 4 SSE BAINBRIDGE IN CHENANGO COUNTY TO 3 S SIDNEY IN DELAWARE COUNTY NEW YORK
    DATE...APRIL 19 2013
    ESTIMATED TIME...753 PM TO 758 PM EDT
    MAXIMUM EF-SCALE RATING...EF1
    ESTIMATED MAXIMUM WIND SPEED...110 MPH
    MAXIMUM PATH WIDTH...200 YARDS
    YARDS PATH LENGTH...3.2 MILES
    BEGINNING LAT/LON...42.2481N / 75.4516W
    ENDING LAT/LON...42.2674N / 75.3939W
    * FATALITIES...0
    * INJURIES...0
    * THE INFORMATION IN THIS STATEMENT IS PRELIMINARY AND SUBJECT TO CHANGE PENDING FINAL REVIEW OF THE EVENT(S) AND PUBLICATION IN NWS STORM DATA.
    ..SUMMARY
    THE NATIONAL WEATHER SERVICE IN BINGHAMTON, NY HAS CONFIRMED THAT A TORNADO TOUCHED DOWN ABOUT 4 MILES SSE OF BAINBRIDGE IN CHENANGO COUNTY...TRACKED NORTHEAST ABOUT 3.2 MILES...AND THEN ENDED ABOUT 3 MILES SOUTH OF SIDNEY IN DELAWARE COUNTY NEW YORK FROM 753 PM EDT TO 758 PM EDT ON APRIL 19 2013.
    THE TORNADO TOUCHED DOWN BETWEEN INTERSTATE 88 AND HIGHWAY 206...ON EAST AFTON ROAD...WHERE 2 POWER POLES WERE SNAPPED AND A CAR WAS DESTROYED BY A LARGE TREE BRANCH. ANOTHER VEHICLE WAS ALSO DAMAGED. SEVERAL TREES WERE SNAPPED OR UPROOTED. A BARN HAD MINOR ROOF DAMAGE. THE TORNADO CONTINUED NORTHEAST AND CROSSED HIGHWAY 206...WHERE A FARM EQUIPMENT BUILDING AND A MOBILE HOME WERE HEAVILY DAMAGED...AND A STORAGE TRAILER WAS DESTROYED. OTHER NEARBY HOMES HAD MINOR DAMAGE...AND A CARPORT WAS LIFTED AND MOVED 75 FEETFARTHER DOWN ITS PATH...THE TORNADO INTENSIFIED TO A HIGH END EF1 STRENGTH WHILE TRAVELING IN THE VICINITY OF HOUCK DRIVE. IN THIS AREA IT UPROOTED OR SNAPPED MANY 1 TO 2 FOOT DIAMETER TREES ALONG ITS PATH...BOTH HARDWOODS /MAPLES/ AND SOFTWOODS /PINES/...WITH THE LARGEST MORE THAN 3 FEET WIDE. IT ALSO CAUSED STRUCTURAL DAMAGE TO A SINGLE FAMILY RESIDENCE AND GARAGE...WHILE TRANSPORTING A SIGNIFICANT AMOUNT OF DEBRIS A HUNDRED YARDS OR MORE. THE TORNADO THEN CROSSED INTO DELAWARE COUNTY...DOWNING SEVERAL MORE TREES ON SOME PROPERTIES ALONG HIGHWAY 8 BEFORE DISSIPATING.
    Here's an SPC archived radar image from 00z, just minutes after the tornado touched down. A noticeable kink can be seen along the squall line near the location of the tornado, along with the approximate track below it:


    Here are some more storm reports from Friday:


  16. Quincy
    Two tornadoes (an EF-2 and an EF-1) touched down in eastern New York on Wednesday, both around 7:00 p.m., according to the National Weather Service (NWS).
    The stronger tornado, an EF-2, had winds of up to 125 MPH and caused damage along a relatively wide and long path. The tornado width was estimated at 1 mile wide with a track length of 17 miles from Florida to Rotterdam.
    The second tornado formed just to the southwest of the EF-2 tornado, around the same time. It was a weaker and shorter-lived tornado, but was associated with the same powerful squall line that was moving east-southeast across New York.
    An upper level shortwave disturbance passed across New York state on Wednesday. Daytime heating across the state helped destabilize the atmosphere. Veering winds aloft created an environment that was conducive for the formation of tornadoes.
    I was actually chasing the EF-2 tornado, but was too far west to catch up to it. Heavy rain, flash flooding and traffic didn't help matters. As I drove into the Rotterdam area along I-90, I noticed cars parked under overpasses. While they may have not witnessed the tornado, I'm sure they experienced strong winds and may have been aware of the Tornado Warning. Personally, I did not see a lot of damage, but the tracks of the tornadoes were mainly south of I-90, which was my route of travel.
    PUBLIC INFORMATION STATEMENT
    NATIONAL WEATHER SERVICE ALBANY NY
    1209 PM EDT FRI MAY 31 2013
    ...PUBLIC INFORMATION STATEMENT...
    TORNADO TOUCHDOWN IN MONTGOMERY AND SCHENECTADY COUNTIES ON WEDNESDAY MAY 29 2013.
    LOCATION...
    BEGAN IN FLORIDA IN MONTGOMERY COUNTY NEW YORK TO ROTTERDAM IN SCHENECTADY COUNTY NEW YORK.
    DATE...05/29/2013.
    ESTIMATED TIME...647-700 PM.
    MAXIMUM EF SCALE RATING...EF-2.
    ESTIMATED MAXIMUM WIND SPEED...125 MPH.
    ESTIMATED PATH WIDTH...1 MILE WIDE.
    PATH LENGTH...17 MILES.
    BEGINNING LAT/LON...42.8457/-74.2034
    ENDING LAT/LON...42.8042/-74.0208
    * FATALITIES...NONE.
    * INJURIES...1.
    * THE INFORMATION IN THIS STATEMENT IS PRELIMINARY AND SUBJECT TO CHANGE PENDING FINAL REVIEW OF THE EVENT AND PUBLICATION IN NWS STORM DATA.
    SUMMARY...PATH WIDTH WAS CONSISTENT ALONG THE ENTIRE PATH LENGTH. MAXIMUM DAMAGE INCLUDED ROOFS TORN OFF OF MULTIPLE STRUCTURES AND HIGH TENSION POWER LINE TOWERS TOPPLED. LARGE NUMBER OF HARD AND SOFT WOOD TREES WERE EITHER TOPPLED...UPROOTED AND OR SHEARED. WIDESPREAD POWER OUTAGES OCCURRED AS WELL.
    ******************************************************
    PUBLIC INFORMATION STATEMENT
    NATIONAL WEATHER SERVICE ALBANY NY
    1241 PM EDT FRI MAY 31 2013
    ...PUBLIC INFORMATION STATEMENT...
    TORNADO TOUCHDOWN IN SCHOHARIE COUNTY ON WEDNESDAY MAY 29 2013.
    LOCATION...
    SUMMIT AND EAST JEFFERSON IN SCHOHARIE COUNTY NEW YORK.
    DATE...05/29/2013.
    ESTIMATED TIME...657 PM TO 702 PM.
    MAXIMUM EF SCALE RATING...EF-1.
    ESTIMATED MAXIMUM WIND SPEED...100 MPH.
    ESTIMATED PATH WIDTH...200 YARDS.
    PATH LENGTH...2 MILES.
    BEGINNING LAT/LON...42.515196/-74.554181
    ENDING LAT/LON...42.522471/-74.578385
    * FATALITIES...NONE.
    * INJURIES...NONE.
    * THE INFORMATION IN THIS STATEMENT IS PRELIMINARY AND SUBJECT TO CHANGE PENDING FINAL REVIEW OF THE EVENT AND PUBLICATION IN NWS STORM DATA.
    SUMMARY...BRIEF TOUCHDOWN ALONG RIDGE LINE SEEN FROM JUNCTURE OF DUTCH HILL ROAD AND WHARTON HOLLOW ROAD. DOZENS OF SOFT AND HARD WOOD TREES FALLEN IN DIFFERENT DIRECTIONS AND SHEARED OFF. ALSO TREES DOWN IN DIFFERENT DIRECTIONS ALONG ENID ROAD AND PERAGLIA ROAD.
    Here's a look at radar imagery at 7:00 p.m. when both tornadoes were on the ground:

    Notice overlap of strong bulk wind shear and MUCAPE leading up to the touchdowns:

    Here's a look at storm reports from across the area:

    Here are the tornado tracks to date (2013) in the region:

    Here's a look at my closest pass to the EF-2 tornado, which was basically at the time that it was reported to have lifted off the ground:

  17. Quincy
    What a challenging forecast and I still think the models have more to resolve, mainly on Sunday with respect to enhancement of snow along a trough.
    Essentially, a light mixture of rain and snow overspreads the region through later today. Across the lower Hudson Valley, Connecticut, Rhode Island and southeastern Massachusetts, I expect virtually no daytime snow accumulation. Low pressure develops south of the area tonight, but the heaviest precipitation and best lift also stays south.
    Some snow falls early Sunday morning and a period of light to moderate snow may develop for a good chunk of the second half of the day, especially across northern Massachusetts and central New England. Here, snowfall totals are forecast to finish in the 4 to 8 inch range by 12:00 a.m. Monday. (Could snow possibly linger later? Yes.)
    We'll see how things continue to change!
  18. Quincy
    The relatively active month of May looks to heat up again in the coming days. After a lot of severe thunderstorm activity last week, the first few days of this week have been on the quieter side. I am looking ahead to three days in particular for the next notable severe weather threats.
    Sleeper Thursday: This day has not been on the radar for most, but offers some potential, even if it is lower-end and in a relatively small area. I am focused on western Texas for isolated supercell/severe potential late Thursday afternoon into the evening hours. A small perturbation/vorticity lobe is modeled to pivot from eastern New Mexico into western Texas late Thursday. At the surface, modest daytime heating will likely result in an area of 1000-2000 J/kg SBCAPE, coupled with approximately 30 knots of 0-6km shear. Although the shear is somewhat marginal for supercell potential and the aerial extent of overlapping parameters is small, the higher resolution models do favor clusters of storms developing in this area.
    Some red flags include weaker winds aloft and storm mode/coverage, but an increasing low-level jet and backing winds around 00z may provide a small window for tornado development. What gets my attention about this event is that it is under the radar and in favorable chase terrain. I do not expect a lot of people to be out and the High Plains have featured several beautiful structure and tornado events this season, so I am not sure I can pass it up. Worst case, I would bail and head north, to get into closer position for Friday.

    Localized outbreak on Friday:
    The model guidance continues to show a strong signal for a severe weather on Friday, with an increased tornado potential across portions of the central Plains. Due to the models speeding up the system just a bit, more forcing and a favorably placed, developing surface low, Friday will probably feature the greatest potential in the otherwise multi-day threat. With the surface low moving into the central High Plains Friday afternoon, the models show strong instability developing across Kansas and Nebraska. The focus appears to be Nebraska, where multiple boundaries/fronts will locally enhance a tornado threat. The warm front is an obvious focus point, as it lifts through Nebraska late in the day. Moving toward late afternoon, the 4km NAM fires a line of discrete storms along a dryline, which will advance eastward through Nebraska and adjacent Kansas ahead of the developing surface low. Look for severe storms along this line, with an isolated to scattered tornado threat. This may extend as far south as sections of north-central Kansas. Along the warm front, the focus narrows in closer to the surface low and warm front/dryline intersection. I would watch the first or second cell closest to that point for a tornado threat. Aside from at least 2000-3000 J/kg SBCAPE (NAM is more like 3000-4000 J/kg), 35-45 knots of 0-6km shear (a bit higher via NAM) and favorable forcing for ascent all favor this severe threat. I imagine that the threat level will be upgraded to Moderate Risk by the Storm Prediction Center (SPC). What makes the threat here a bit more robust than some previous days is that we are not seeing a strong signal of convective debris or MCS activity overturning the atmosphere prior to peak heat. If there should be any convection in the morning, it would likely be limited in coverage, and outflow from that activity may only serve to further enhance the threat by leaving additional boundaries in place. Another quick note is that depending on how wrapped up the surface low becomes, the threat may punch northward into southern portions of South Dakota, especially into Friday evening.
    It is hard to really outline any significant red flags for Friday. There is the question of storm coverage, but a higher-end event in this case is actually favored when storms are more isolated. Precipitable water values are also expected to be lower than some recent events, so that further mitigated an MCS threat. I suppose there could be storm mergers and some messy storm mode eventually, but all in all, I think this is a bonafide threat and certainly a day to get out and chase.

    Messy mayhem on Saturday:
    The setup, overall, has a lot of similarities to last Saturday. It is likely that some junk convection and MCS activity in the morning will mitigate the threat. Also, the mid to upper level flow looks rather southerly, which is not ideal, as forecast soundings show veer-back-veer issues. With that said, if there are pockets of moderate instability, as the models indicate, there should still be corridors of an enhanced severe threat. This includes tornadoes, as 0-6km shear looks to be at least 40-50 knots and probably higher across some western areas of the threat zone. The red flags win out here, but there is time for this to change. In terms of chase potential, it will take some patience and strategy. Even last Saturday did result in clusters of tornadoes. With this threat being furthest out and potentially disappointing, I will not spend too much time focusing on it at this point. Of course, trends will be monitored and the threat will continued to be monitored.
  19. Quincy
    As the calendar passes deeper into June, there is typically a steady drop-off in the frequency of severe weather threats across the U.S. Last year featured a grand finale to the severe weather season with a fairly significant sequence or tornado events across portions of the north-central U.S. from June 16th to 18th. While this year will likely not see quite an intense show as June 2014, there could very well still be some respectable severe activity with tornadoes.
    Mid-June of this year has been on the radar, so to speak, for quite some time. While there are still some model differences, it would appear that at least a couple of days between Thursday, June 18th and Sunday, June 21st should feature at least localized severe weather events. Note that there is some isolated potential before June 18th, this article will focus more so on the 18th onward.
    With it only being the 15th and plenty of time for forecasts to change, it is too soon to get into specifics. There are at least two main ingredients that would appear to favor severe weather, more-so, perhaps, than the U.S. has seen over the past week or so. Strong to possibly extreme instability is projected to be in place. Both the GFS and Euro show sizable areas of of 3000+ J/kg MLCAPE. The upper level flow is shifting toward a more zonal pattern, at least in the larger scale. An increasingly tight height gradient is likely from the central/northern Plains into portions of the Midwest by the end of the week and into the weekend. This is expected to result in a stronger component to the winds in the upper levels. The result is favorable forcing aloft and enhanced wind shear with any shortwave energy that ejects through.
    There are always caveats and red flags. While there may be more severe weather ingredients to work with, the overlap of those parameters may be relatively small. For example, while 500mb flow may be in excess of 50 knots for a time during this period, the best instability will almost certainly remain displaced well to the south and east. This in itself should tend to favor a more localized severe weather risk. Nonetheless, the Euro and especially the GFS progs over the past several runs highlight(ed) the period in and around June 18th to 21st. The potential exists for severe weather, possibly significant, including tornadoes somewhere in the region between the northern half of the Plains to the western Great Lakes. At the very least, some high CAPE/low shear setups are likely. The questions will become, how large can the threat zones extend and will some of the more impressive shear overlap with stronger instability?
    Take a look at some forecast soundings for this weekend if you want some severe weather eye candy. It is silly to take these progs too seriously at this point, so we will have to wait and see how the forecasts evolve. A broad geographical area is highlighted here and it will not be until the short-term that exact threat zones can be confidently identified. Nonetheless, at least one or two solid chasing days are predicted between Thursday and Sunday. If you are willing to travel or on a chasecation, there is reason to be cautiously optimistic about the storm chase potential coming up.
  20. Quincy
    For the fourth year in a row, overall severe thunderstorm activity, including tornadoes, finished below average across the Lower 48. This graphic shows the severe thunderstorm watch departure from the 13-year average. The vast majority of the U.S. saw at or below average numbers of severe thunderstorm watches. The greatest departures from average were across the central Plains into parts of the Midwest. The only state with more severe thunderstorm watches than average was Texas, with a higher instance of watches over parts of central to southern Texas. What was the cause for this, aside from the seemingly long-term lack of severe thunderstorm activity?
     
    The 2015 severe weather season actually got off to a relatively fast start from late March into early April, remaining active into much of May. Attention shifts toward June, which is usually the the peak of the season. June 2015 featured substantial ridging across the western U.S. While not the sole factor, that ridging was a big player in the relative lack of severe thunderstorm activity into June. The severe season climatologically focuses in to parts of the central and northern Plains in June, but the 500mb height pattern in June 2015 was not the most favorable for severe thunderstorms. Some troughing evident over the Great Lakes favored multiple severe weather events across the Midwest and Ohio Valley. However, even here, the season, overall (not in all cases), was on the quieter side.

    Above image shows 500mb heights and anomalies for June 2015.
    The overall tornado activity in 2015 was below average, but some parts of the country did see an increase in activity compared to recent years. Portions of Iowa and northern Illinois saw a very active tornado season. This included an early season outbreak on April 9th and a fall event on November 11th. Texas also saw an active season, particularly in North Texas. The High Plains saw a broad area of increased activity, particularly from the Texas panhandle into eastern Colorado and western Kansas. The other part of this graphic that stands out is the lack of tornado watches across the Deep South. Given recent trends and forecasts, it is conceivable that the severe season over the Gulf Coast states, including Florida, may remain on the active side over the next few weeks. Deeper into the year, it is a bit more unclear if March and April will see an uptick in activity across Dixie Alley. Only time will tell.

  21. Quincy
    The potential exists for a low-end severe weather outbreak across portions of the Plains this weekend, April 12th-13th.
    The first focus is on Saturday afternoon into the overnight period across the central Plains. Surface low pressure is forecast to move to a position in the vicinity of the Oklahoma panhandle by 00z Sunday. Now while there is good agreement among the models of destablization in the warm sector, capping will likely mitigate any convective activity for most of the day. However, by late afternoon and into the evening hours enough of the CAP may erode to allow for some isolated severe thunderstorms.
    In the upper levels, a broad positively-tilted trough is projected to be crossing the Rockies late Saturday. The NAM and GFS show an embedded, but small vortmax being ejected northeast from Kansas toward the Missouri/Iowa border Saturday night. Wind fields are not overly impressive and the 18z NAM low level jet appears overdone. With that said, at least 30 knots of bulk wind shear is modeled.
    CAPE values via the NAM and GFS exceed 2000 J/kg from Oklahoma up into Kansas and northern Missouri. The Euro has increased instability somewhat from the 00z run, but only maxes out values around 2000 in eastern Kansas. Given the amount of CIN that has to be overcome, the severe potential here is marginal at best. Given the time-frame three days out, the exact positioning and severity of this threat could shift.

    A somewhat more favorable severe setup may develop on Sunday. As the upper level trough digs into the southern Plains, surface low pressure deepens and slides southeast through Oklahoma and into northern Texas. With the trough axis approaching a neutral tilt, the overall dynamics alone become supportive for severe thunderstorms.
    At the surface, low pressure matures across far northern Texas Sunday afternoon as a strong cold front quickly dives south. A moist southerly flow will aid with moisture transport as dew-points move into the mid and upper 60s. The GFS also shows lifted indicies as low as -12. Ahead of the dryline, a moderately unstable air-mass is forecast on both the GFS and Euro. The GFS has 1500-2500 J/kg of CAPE across eastern portions of Texas into southern Oklahoma with the Euro showing similar instability levels. There should not be much capping, so convective can initiate ahead of the dryline with isolated supercells possible in the warm sector as well.
    Kinematic support increases with bulk shear in excess of 50 knots possible further south of the low across Texas. While damaging winds and hail may be the most significant threats, the setup may also be supportive of at least a few tornadoes. Severe thunderstorms could continue into early Monday, with at that point the cold front should have overtaken the dryline. The result would be more of a squall line with potentially damaging winds than discrete supercell structures. If the somewhat faster GFS is correct, the threat would extend further east into Arkansas and Louisiana.
    While confidence is greater in the severe threat on Sunday, a faster-moving cold front or weaker storm system could alter the forecast. There is relatively narrow window during the second half of Sunday that this system must align with in order for severe weather to be a significant concern. A quick note that the 18z GFS has trended toward stronger kinematic support for Sunday.
  22. Quincy

    Severe Weather Sunday

    By Quincy,

    Severe thunderstorms are likely today across portions of the Plains and Mississippi River Valley.
    Ongoing thunderstorms early this morning may be marginally severe across portions of Iowa, northern Missouri and Illinois. Additional showers and thunderstorms are likely from late morning into the early afternoon hours further south before a more serious threat develops.
    Sunday afternoon, low pressure will be in the vicinity of the central border between Texas and Oklahoma. An upper level shortwave will begin to rotate through the area with a vortmax swinging into eastern Oklahoma. Thunderstorms will likely fire just ahead of a dryline during the afternoon hours. These thunderstorms can explosively develop, producing large hail, damaging winds and at least a few tornadoes.
    The greatest potential for tornadoes will be from extreme northeast Texas into eastern Oklahoma. There is some uncertainty with respect to how far north this threat will extend, but the area south of the KS/OK/MO tri-state border has the highest probability of seeing tornadoes. There is high confidence that there will be numerous severe reports, but it is not clear over how large of an area the most intense storms will extend.
    Climatology suggests that the tornado threat could extend further east into Arkansas and southern Missouri late Sunday night into early Monday. Although this is possible, a loss of heating and a cold front overtaking the dryline should mitigate the risk after 12 a.m. Monday.
  23. Quincy
    As the pattern over North America shifts, an extended period of potential severe thunderstorms targets the central U.S. Although this update covers May 6-10, thunderstorms are ongoing today (May 5th) and were prevalent in prior days as well. The difference here is that we are gradually starting to see more and more potentially potent setups on the horizon.
    Wednesday, May 6th: This day has been on the radar for a while and things are coming into somewhat better focus. As shortwave energy pivots from the High Plains to central/northern Plains on Wednesday, an area of surface low pressure will develop. With more forcing in place than prior days, that alone signals an enhanced severe weather threat.
    —
    By Wednesday afternoon, a portion of the surface low should be crossing over from far eastern Colorado into western Kansas. The strongest forcing should reside from northwestern Oklahoma into central Kansas. However, the greatest instability will likely be displaced further south from central Oklahoma down into north Texas.
    Partial to considerable cloud-cover will tend to limit the amount of destabilization that takes place. That combined with modest flow at 500mb, progged to be on the order of about 35 to 45 knots, will tend to limit the extent of the severe weather potential. The surface low itself is also a bit elongated. If it were more concentrated and also deeper, that would signal a greater severe thunderstorm potential. Nonetheless, with a tongue of 1,000 to 2,000+ J/kg CAPE, favorable speed and directional shear, and some forcing aloft should favor at least scattered severe thunderstorms by mid to late afternoon.
    —
    In terms of severe threats and the areas to watch…
    It comes down to northwestern Oklahoma into central Kansas for what should be the greatest severe threat. More isolated severe storms are still possible along a dryline down into western and central Texas. Large hail, perhaps very large in a couple of storms, appears to be the most significant risk. Damaging winds will be possible, especially into the overnight as storms may tend to merge into lines. There is a tornado threat, which should be maximized during the early evening hours, as the low level jet ramps up. As has been the case many times this year, while there is an evident tornado threat, the intensity and duration of any tornadic storms will be dampened somewhat by the limiting factors mentioned above. There is a fairly good likliehood that multiple tornadoes (but not a major outbreak) will be reported late Wednesday afternoon into Wednesday evening.
    Thursday into Friday, May 7th and 8th, also provide some severe weather threat, but in a more isolated and sporadic nature. Upper level heights should remain fairly neutral through the period with no significant forcing noted in the models. Each day is likely to feature moderate instability and at least marginally supportive wind shear for supercell thunderstorms. The corridor for this period should be narrowed in on the Texas panhandle, portions of interior Texas and into Oklahoma. While some severe threat may nudge into portions of Kansas, the greatest (still somewhat limited) threat should hang back further south. Each day, storms may produce large hail with some damaging winds and a few tornadoes.
    —
    Each day, watch for a few things: First, where is the greatest instability? If cloud-cover and convective debris are limited during the morning, expect a somewhat enhanced severe weather threat during the afternoon. Also, look for any outflow or other mesoscale boundaries that can be the focal point(s) for storm development. Finally, notice any upper level perturbations, even if seemingly minor, as they could provide just enough forcing to locally increase the severe threat.
    Saturday, May 9th has the potential, but the keyword is potential, to be a significant severe weather outbreak with numerous tornadoes. The overall pattern is favorable, as a trough swinging from the Four Corners region to eastern Colorado/New Mexico by late-day will provide ample forcing from the High Plains into portions of the central to southern Plains. Caution must be applied when looking at the analogs, but there is a fairly strong signal from the analogs that favors widespread severe thunderstorms and at least isolated significant severe events, including strong and/or long-track tornadoes.
    —
    Now, even though some major events show up in the analogs, there are a few limiting factors that will not favor a high-end outbreak. While the flow and forcing increase aloft, 70-80 knots at 300mb and 50-60 knots at 500mb will fall well short of an event such as 4/14/12, which showed up as a GFS-based analog. As far as instability, even though moderate CAPE values are predicted, we’re not looking at strong to extreme instability. There seems to be a common theme, with this week especially, that the atmosphere is not quite taking full advantage, resulting in a less extreme “than possible” setup.
    —
    With all of this said, even if the timing is not exactly right, and the timing looks pretty favorable right now, severe thunderstorms are strongly favored on Saturday. What will be the difference between a low-end event and a more significant outbreak will come down to mesoscale details. What also favors severe weather on Saturday is how the models, overall, have been in very good agreement with the general setup on Saturday for quite some time. The focus on Saturday ranges from north Texas through much of Oklahoma and Kansas, to perhaps as far north as portions of Nebraska. All severe weather modes are anticipated, with an enhanced risk of tornadoes.
    Sunday, May 10th is a bit further out there, but yet another severe day is quite possible. Details are a bit more muddled, as the evolution of Saturday will have a sizeable impact on what transpires on Sunday. The threat zone inches somewhat east, ranging from portions of Texas up through central and eastern Oklahoma, eastern Kansas and perhaps into portions of Missouri and Arkansas.
    In summary, expect severe weather threats for the rest of this week and likely through most of this weekend across the central U.S. At least a few severe thunderstorms are expected each day, with scattered severe storms on Wednesday and perhaps a mode widespread and significant event on Saturday. Tornadoes are possible each day, but the day with the likelihood for the most tornadoes is also Saturday. In terms of storm chasing, there should be many quality opportunities to get out in prime real estate, from the High Plains into the Plains west of I-35. With the threats covering a long period over some similar areas, it may be worth while to hunker down and start thinking of possible targets or even just places to stay (if you’re planning a multi-day trip). Without giving too much away, and since details may change, I tend to favor a corridor from the Texas panhandle into southwest and central Kansas. Climatology also favors this zone for the greatest severe weather threat and trends this year have kept the dryline a bit further west, mainly across these areas, during most events.
  24. Quincy
    An upper level trough across the Great Lakes is associated with areas of surface low pressure in and around New York State. Bands of showers and thunderstorms have been pinwheeling through the eastern United States as a result. By afternoon, more organized thunderstorm development is expected and some storms could become severe.
    Isolated severe thunderstorm threat...
    Low pressure is spinning across New York State. An area of increased wind shear is in place along the east of the Appalachians. Satellite imagery has indicated that much of the region has broken out to at least partial sunshine. This is creating moderately steep lapse rates and with cooler temperatures aloft associated with a 500mb trough, that steepness continues into the mid-levels. A rich southerly flow continues to keep dew-points on the higher side with most stations in the upper 60's to lower 60's.
    As far as forcing goes, there there is a weak frontal boundary movingly slowly eastward across the Appalachians. The higher resolution models couple that disturbance with an unstable air-mass and develop isolated thunderstorms and broken line segments across the Northeast by mid-afternoon.
    Some of the obstacles include a marine influence and some shower activity across southern New England, which may limit just how much the atmosphere can destabilize. However, elevated amounts of wind shear can promote updraft formation and some strong to severe thunderstorms. The coverage of these storms is not anticipated to be widespread in New York and New England. With cooler 500mb temperatures, there is a marginal hail threat with some of the stronger updrafts. Damaging winds seems to be the biggest concern with a relatively low, but still mention-able tornado threat, especially given the relatively low ML LCL's. Climo would not favor widespread severe activity given a south wind, but a coastal front could have some interaction with the upper level setup, which may slightly enhance convective activity.
    Convection is trying to initiate as of midday, but the focus is from early to mid afternoon across the Appalachians and late afternoon in southern New England for any strong to potentially severe storms.
    Numerous severe thunderstorm threat...
    Further south, stronger wind shear combines with more impressive daytime heating to warrant a threat of numerous strong to severe thunderstorms. The focus for this extends from southeastern Pennsylvania and western New Jersey and points southwest. Here there is a threat of large hail, damaging winds and also isolated tornadoes, especially given bulk shear values near or possibly above 50kts this afternoon.

  25. Quincy
    Low pressure develops across Pennsylvania later today and I am expecting at least some isolated severe thunderstorms across the region.
    Isolated thunderstorm threat...
    Satellite imagery shows mostly clear skies with just some high clouds across eastern Pennsylvania and New Jersey. Daytime heating is expected to push surface temperatures well into the 80's along with dew-points that are already in the upper 60's to lower 70's. In the warm sector well ahead of a cold front (east of the Appalachians in the mid-Atlantic states), a few thunderstorm cells or clusters could develop and become marginally severe this afternoon. As the cold front approaches, a squall line is depicted on the higher resolution models. This may cause isolated wind damage, especially across eastern Pennsylvania and western New Jersey. NAM forecast MLCAPE values are modest at best, near 1000 J/kg in spots. Some hail is possible in the stronger storms, but large hail is not a major threat. Due to the relatively late timing, the severe threat is a bit more unclear across portions of New York State. Even with a loss of daytime heating, proximity to deepening low pressure may cause strong to isolated severe thunderstorms to continue into the overnight period and through the pre-dawn hours of Friday. Although the threat is relatively low due to a lack of directional wind shear, the northern portion of this isolated threat zone will see increased shear after sunset as low pressure amplifies. The late timing does not climatologically favor nighttime tornadic development, but a quick spin-up could be possible, mainly in northeastern Pennsylvania, northwestern New Jersey and portions of southern New York State.

    In Connecticut...
    Although skies are breaking for sunshine across southwest portions of the state, there is a lack of a trigger mechanism to fire off any storms. MLCAPE values may increase to near 500 J/kg in parts of the state. SBCAPE looks more impressive, but with poor mid-level lapse rates, severe thunderstorm activity is not anticipated. Some pop-up thunderstorms are possible late in the afternoon and some embedded thunderstorms are expected overnight, especially west of the Connecticut River.
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