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Upcoming Severe Threats: 5/1

The final few days of April finished on the quiet side in terms of severe and that continued into May 1st. With that said, a larger-scale pattern change is likely to be accompanied by multiple threats of severe weather in the coming days. Saturday 5/2: Not seeing anything major here. Although we should finally see some modest instability up into the central Plains, dew-points are only expected to rise into the upper 40s to lower 50s across the area with some weak forcing during the evening. One plus is that wind shear will be supportive of supercell structures, assuming other variables line up. Verdict: A few, rogue severe thunderstorms are possible from late afternoon into the evening, but even those may only be marginally severe. The focus is on the central Plains
Sunday 5/3: The setup looks slightly better than Saturday, but that does not say much. A larger area can expect modest to moderate instability, but the drawback here is near-neutral height tendencies. Upper level progs show little focused area of forcing. The only thing that looks somewhat interesting is a surface low forming near the Colorado/Kansas border. This could narrow the focus on some isolated severe thunderstorms to the Texas and Oklahoma panhandles, but even here the prospects are not terribly exciting. If there is enough of a trigger, a few isolated strong to severe storms could also initiate up into the central Plains and as far east as the upper Midwest. Wind shear is questionable throughout the regions outlined. Verdict: Isolated severe thunderstorms are possible anywhere from the southern High Plains into the central Plains and upper Midwest. If there is one area to focus in on, it might be just ahead of a surface low, in the vicinity of the Texas/Oklahoma panhandles. While the ceiling may be somewhat higher than Saturday, storm coverage and intensity is not expected to be particularly impressive.
Monday 5/4: This looks like the beginning of what may be an extended period of active weather. A trough should begin digging into the West Coast, with some modest height falls reaching the High Plains. Moisture will likely be a positive and negative thing here. Although dew-points should reach the upper 50s to lower 60s at a minimum, cloud-cover, convective debris and increasing precipitable water values throw a wrench in the severe storm potential. Likewise, wind shear is not expected to be terribly impressive either. What may end up ultimately happening is that a few pockets of greater instability could lead to a few supercells reaching severe limits. Verdict: Mixed signals somewhat hamper the severe potential, but it would appear probable that at least a few isolated to widely scattered severe thunderstorms could develop from the Texas/Oklahoma panhandles into Kansas.
Tuesday 5/5 through Thursday 5/7: The Euro and GFS are actually in very good agreement overall through the period with the general pattern. The West Coast trough continues to dig and a piece of energy swings through from the High Plains on Tuesday into the central Plains on Wednesday. Tuesday looks muddled at best with meager instability and limited kinematic support. Wednesday may offer the best potential, if things line up. Shortwave energy should be pivoting into the central Plains, along with a surface low, but that low looks awfully elongated. The instability setup may suffer too, from limited instability and on-going clouds/sub-severe storms. With that said, a low level-jet should be cranking with both the Euro and GFS suggesting at least 40-50+ knot winds at 850mb. Thursday becomes a bit more unclear, despite continued model agreement. Storms may be ongoing Thursday morning, based on current trends, and the models seem, perhaps, a bit overdone with instability in the warm sector. Even so, wind shear looks to slacken off, which could be another factor to limit the severe threat. Timing is yet another concern, as a faster evolution could really hinder the Thursday risk, whereas a slower scenario might be better. Verdict: Some isolated to scattered severe thunderstorm potential each day, but details are still unclear. Wednesday may offer the greatest potential with Thursday being a wild card.
The worst case is that this upcoming week, there are just a few severe thunderstorms, but enough of a threat to track for a few days in a row. The best case is that things come together for one to possibly two decent chase days.

Quincy

Quincy

 

May 2015 Tornado Forecast

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.

Quincy

Quincy

 

Violent U.S. Tornadoes: 1962-2011

Over a 50-year span from 1962 to 2011, the most violent (F/EF-4 and F/EF-5) tornadoes occurred over Oklahoma and Mississippi. The maximum grid-points reported 16 over that period, with two of those grid-points in central Oklahoma and one in central Mississippi. While a broad area from the Plains to the mid-South sees the most tornadoes overall across the United States, there are three sub-areas with the most violent tornadoes. Much of Oklahoma falls into that category, as it is widely considered to be in the heart of tornado alley. Further north into Iowa is another area that has seen the most violent tornadoes during the period. The third area falls across Mississippi, where the tornado season is relatively elongated from the heart of winter into mid-Spring. The tornado season in Oklahoma generally occurs in a narrower window in mid-Spring. The season in Iowa tends to fall from mid to late spring with a secondary peak in the fall. A smaller and less significant maximum for violent tornadoes can also be identified across the upper Ohio Valley. While the tornado season tends to peak there in mid-Spring, a few events have also occurred in the fall. An interesting tornado minimum occurs in a small portion of central Missouri. Among multiple factors is the unique geographical area Missouri falls into. The classic tornado setup in the Plains is driven largely by lee-side cyclogenesis and the dryline. As storm systems move across the Plains, the bulk of the violent tornadoes tend to occur west and northwest of Missouri. Also, the dryline tends to have trouble advancing enough east to penetrate far into Missouri. Likewise, typical tornado events in the mid-South tend to thrive off of moisture from the Gulf of Mexico, producing tornadoes east of Missouri. With that said, higher instances of violent tornadoes have been noted across northwestern Missouri (tornado alley), far southeastern portions of the state (Dixie alley) and the devestating EF-5 tornado in Joplin, in far southwestern Missouri in 2011. East of the Appalachians, violent tornadoes are fairly uncommon. However, two particular regions have reported three or more violent tornadoes from 1962 to 2011. Portions of the Carolinas fall into that category. Further north, grid-points in the mid-Hudson Valley into southwestern New England have reported four violent tornadoes in that same span.

Quincy

Quincy

 

Connecticut Snowfall Totals: Mar. 20-21, 2015

Here is a snowfall map 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. Snow developed during the afternoon on March 20th across Connecticut. Dry air in place prior to the event resulted in several hours of virga until ground observations finally reported snow early in the afternoon. Snow overspread the state, but the snow was heaviest across southwestern sections. The snow continued overnight as low pressure developed east of New Jersey. Periods of light snow continued into the morning hours on March 21st. There was some enhancement of the snow across central Connecticut before the snow tapered to flurries statewide by midday. Snowfall totals ranged from 4 to 7 inches across southwestern Connecticut to just under 2 inches in northeastern Connecticut. Much of interior Connecticut reported 2 to 4 inches with a few isolated higher amounts in north-central portions of the state. A narrow band across the higher elevations of Fairfield County, just northwest of the Merritt Parkway, reported locally 7 to roughly 8 inches of snow.

Quincy

Quincy

 

Connecticut Snowfall Totals: Mar. 1-2, 2015

Here is a snowfall map 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. Periods of light snow developed across Connecticut between late morning and early afternoon on March 1st. The snow became moderate to briefly heavy at times during the evening hours. Snow tapered off across northwestern Connecticut by midnight, but lingered in eastern areas until the pre-dawn hours on March 2nd. The heaviest snow affected the I-95 corridor and a bit further north into eastern Connecticut. This event resulted in a general 3 to 6 inch snowfall around the state. The lowest amounts were reported in far northwestern Connecticut with near or just under 3 inches. A few spots in the southeastern half of Connecticut saw 6 to 7 inches of snow.

Quincy

Quincy

 

Connecticut Snowfall Totals: Feb. 21-22, 2015

Here is a snowfall map 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. Areas of weak low pressure moved through the Ohio Valley along a frontal boundary on February 21st and periods of light snow moved into Connecticut during the afternoon. The snow gradually became moderate to briefly heavy at times during the evening. Due to the frontal boundary being west of the state, winds were generally out of the south to southwest ahead of low pressure, through the event. This led to temperatures rising into the lower 30s overnight. Snow changed to sleet, roughly as far northwest as I-84. A narrow corridor of freezing rain was reported just to the northwest of I-95. Some areas changed to plain rain south and east of I-95 along the coast and east of I-395 in far eastern Connecticut. Precipitation changed back to snow in all areas before ending on the morning of the 22nd. Most of the state reported a 4 to 8 inch snowfall. A few totals just over 8 inches were reported in Litchfield and Tolland counties. Snowfall totals along and southeast of the I-395 to I-95 corridor were generally in the range of 2 to 4 inches. The immediate shoreline in southeastern Connecticut reported around or just under 2 inches.

Quincy

Quincy

 

Connecticut Snowfall Totals: Feb. 14-15, 2015

Here is a snowfall map 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. As low pressure moved east from the Great Lakes, some modest warm advection light snow developed around Connecticut during the morning and afternoon on February 14th. The snow was intermittent and amounts were generally less than two inches during the daylight hours. The storm system rapidly intensified east of New England overnight and some bands of moderate to heavy snow rotated through eastern Connecticut. The snow tapered off on Sunday, during the morning in most areas, but not until early afternoon near the Rhode Island border. Snowfall totals ranged from less than two inches across far western and southwestern Connecticut, to four to eight inches across most eastern portions of the state. A few totals up to nine inches were reported, across the hills of Tolland County and across southeastern Windham County.

Quincy

Quincy

 

Connecticut Snowfall Totals: Feb. 7-9, 2015

Here is a snowfall map 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. This event was spread out over three days as low pressure passed along a frontal boundary, draped from the Ohio Valley into southern New England. On the first day, Saturday, February 7th, occasional flurries and a few bands of light snow passed through Connecticut. Snowfall totals on this day were generally an inch or less around the state. On Sunday, February 8th, scattered snow showers and flurries continued. During the evening hours, a band of heavier snow developed from roughly Danbury to Meriden. Outside of that band, daily snowfall totals were mainly less than two inches. Snow across Connecticut, especially northern portions of the state, became steadier after midnight. Snow, heavy at times, continued through much of the day on Monday, February 9th. The heaviest snowfall affected the northern portion of the state. Snow finally tapered off during the evening hours in Windham County. The majority of the total snowfall from this event occurred on Monday. Through the event, there was some mixing with sleet, graupel and freezing drizzle across the southern half of Connecticut. Mixed precipitation was the dominant precipitation type in lower Fairfield County and much of New London County. Some shadowing of snowfall totals can be noted west of the hills in northwestern Connecticut and across the Connecticut River Valley. There, snowfall totals were generally 4 to 8 inches. Some localized 8"+ snowfall amounts were reported in west-central Connecticut and across some of the higher elevations in Tolland and Windham counties.

Quincy

Quincy

 

Connecticut Snowfall Totals: Feb. 1-2, 2015

Here is a snowfall map 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. Occasional flurries developed on Sunday, February 1st across Connecticut. A steadier snow moved in after midnight with some moderate to heavy snow during the morning hours on February 1st. By 7 to 8 a.m., precipitation changed to sleet across lower Fairfield County. Snow mixed with and changed to sleet in most areas up to roughly I-84 from mid to late morning. There was some spotty freezing rain as well, mainly for a short time near the I-95 corridor. As colder air worked in behind a low pressure system passing by east of Long Island, precipitation quickly changed back to all snow across the state. An intense band of heavy snow formed across western Connecticut and moved from west to east across the state. This band of snow was producing 2″+ per hour snowfall rates. Snow quickly tapered off by mid-afternoon in western Connecticut and by early evening near the Rhode Island border. The majority of the state saw anywhere from 8 to 12 inches of snowfall. Locally higher amounts were reported in the northwestern and northeastern hills. Southeastern Connecticut, where there was the longest period of sleet and freezing rain, had anywhere from about 5 to 8 inches of snowfall.

Quincy

Quincy

 

February 2nd Snow & Ice Forecast

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.

Quincy

Quincy

 

Blizzard of 2015 Snowfall Totals: Connecticut

Here is a snowfall map 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. Periods of light snow and flurries began on the morning of Monday, January 26th and continued through the afternoon. It wasn't until after dark that the snow became heavy at times, particularly across the eastern half of the state. Although western sections hung on to a steady snow, it was generally light to moderate. A band of intense snowfall set up near I-395 in eastern Connecticut during the early morning to predawn hours on the 27th. The band of snow dropped 2 to 4 and occasionally 5 inches per hour for a few hours. During the day on the 27th, periods of light to occasionally moderate snow continued across eastern Connecticut, while only a few stray flurries affected western portions of the state. A couple of bands of briefly heavy snow hit northeastern Connecticut on the night of the 27th. The last flurries ended early on the morning of the 28th across Windham County. This is where the highest amounts were found. I-91 was an approximate divide between less than a foot to the west and over a foot to the east. Over two feet of snow was common from northern New London County into much of Windham County. For some of these communities, this was the most significant snowfall since the Blizzard of 1978.

Quincy

Quincy

 

Final Snowfall Forecast: Blizzard of 2015

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.

Quincy

Quincy

 

Snowfall Forecast: Blizzard of 2015

A major snow storm is projected to bring blizzard conditions to much of New England Monday night through Tuesday. When all is said and done, many areas in and around the Boston area can expect two feet of snow with locally higher amounts. Despite the European model staying the course with greater snowfall amounts for areas around New York and New Jersey, it appears that most other data favors sharply decreasing snowfall amounts west of southern New England. As low pressure rapidly intensifies and moves toward Cape Cod and the islands, snow will become heavy with strong winds and blizzard conditions along the I-95 corridor from New York City to Boston and downeast Maine. As low pressure nearly stalls and does a loop, similar to historic blizzards in the past, a band of intense snowfall should drop excessive to possibly historic snowfall amounts. It appears that the likely positioning of this band would be on a SSW to NNE axis between central/eastern Connecticut and interior eastern Massachusetts. This may include the Boston metropolitan area. Although mesoscale details of such a band are not 100% clear, the potential exists for some 30"+ totals where this band sets up. Snow in this area will persist through the second half of Tuesday, before finally winding down early Wednesday morning. Here is the thinking for this storm. The greatest bust potential lies across far western New England, New York State, New Jersey and points west. Although this forecast leans closer to the more eastern GFS/NAM/RGEM solutions, it will still be interesting to see how the 00z Euro trends. It is very rare for the Euro to cave to the other models inside of 72 hours, but it is also hard to believe that it will stay as far west with the heavy snow as previous runs have. Another consideration is that liquid to snow ratios, especially across the interior high terrain, will be greater than 10:1. Ratios in the range of 14-18:1 across western and central Massachusetts should help offset some lower precipitation amounts with a considerable fluff factor. 8:30 a.m. Monday edit: The models have compromised a bit overnight, but the RGEM is still rather light with snowfall amounts across western New England and points west.

Quincy

Quincy

 

Connecticut Snowfall Totals: Nov. 26-27, 2014

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.

Quincy

Quincy

 

Snowfall Forecast: Nov. 26-27, PHL-BOS

An early season storm is expected to bring a heavy, wet snow to the interior hills of the upper mid-Atlantic region and New England on Wednesday into very early Thanksgiving morning. While the big cities from Philadelphia to New York and Boston can expect some snow, the greatest amounts will be to their north and west. Low pressure will develop along the Carolina coast this morning and ride up the East Coast. With the low passing close to, if not over Cape Cod, no strong high pressure center in place to the north and the fact that we're still in November, a warm surge of air should penetrate up to and even a bit northwest of I-95. While temperatures from 850mb down to the surface may hover near freezing, a warm layer up around 800-700mb will likely cause melting aloft, meaning there will be sleet and rain. The result is anticipated to be heavy wet snow well inland, but quite a bit of sleet across areas such as New Haven, Willimantic and the western Boston suburbs, with a change to rain in areas including Providence and Taunton. New York City and Philadelphia look to be in a bit of a different scenario, where rain will try to change to wet snow during the day on Wednesday. The time of day will not be favorable, along with the somewhat inland 700mb low track. The heaviest snow should fall from late morning through the afternoon across northern New Jersey and the mid-Hudson Valley. The hills of interior Massachusetts and central New England should see widespread snowfall amounts over 10" with the heaviest falling from the afternoon into the evening hours. 10 to 12" will be common with a few locally higher amounts possible. Due to the localized nature of 12"+ totals, they have been omitted from this map. Snow will taper off to snow showers early Thanksgiving morning and a few flurries could linger into the day in some locations. Snowfall forecast totals for the big cities: Boston: 2 to 4 inches Worcester: 8 to 12 inches Providence: 2 to 3 inches Hartford: 6 to 9 inches New York City: 1 to 3 inches Philadelphia: 1 to 3 inches

Quincy

Quincy

 

Connecticut Snowfall Totals: Nov. 13-14, 2014

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, with light snow across the higher elevations, developed across Connecticut during the evening hours of November 13th. The steadiest and heaviest snow fell around midnight and tapered off during the pre-dawn hours on November 14th. Most locations eventually changed to snow, with the exception being the immediate shoreline and urban coastal corridor from New Haven down toward the New York border. On average, the hills saw anywhere from 1 to 3 inches of snow, with generally an inch or less across the valleys and shoreline. The highest amounts around and just over 3 inches were reported in Litchfield County.

Quincy

Quincy

 

U.S. Tornado Days Per Year

The United States has a greater frequency of tornadoes than most other counties. For many factors, the vast majority of tornadoes occur east of the Rocky Mountains across the continental U.S. Although the central and southern Plains region is widely considered to be "Tornado Alley," there are other areas that see just as many tornadoes, if not even more. The two graphics below are adaptations of NOAA/NWS SPC graphics found in their Tornado Environmental Browser. A broad area from the east slopes of the Rockies east to the west slopes of the Appalachians typically see the most days with tornadoes per year. Two local maximums can be identified in northeastern Colorado and central Florida. While these areas may see numerous tornadoes in any given year, they are generally low on the EF-scale. The central Appalachians feature a local minimum of tornadoes, but as one travels east, the frequency of tornadoes increases. While terrain by itself will generally not have much of an effect on a tornado, especially a significant (EF/F-2 or stronger) one, there are reasons why terrain affects tornado frequency. In the Plains, lee cyclogenesis combined with a surge of warm, moist air from the Gulf of Mexico and drier air from the Rockies tends to create a favorable setup for severe thunderstorms and tornado development. Across the East Coast, there is less real estate to work with when considering the proximity to the Atlantic Ocean. Also, wind out of the south to southeast in the lower levels will often mitigate the risk of severe thunderstorms, especially in the spring and early summer months from the mid-Atlantic region into the Northeast. The placement of a "Bermuda" high and/or a "southeast ridge" of high pressure will tend to limit the formation of strong non-tropical low pressure systems along the East Coast during the warmer months, as the jet stream is often displaced further northwest. The frequency of days with significant tornadoes is in some ways similar to, but also has differences in comparison with the frequency of days with all tornadoes. While portions of Colorado and Florida may see the most tornadoes overall, there are two distinct areas that feature a much greater frequency of significant tornadoes. The southern Plains into Dixie Alley (lower to mid-Mississippi Valley) will on average experience the most significant tornado outbreaks. Here, there are three factors that are probably most responsible for this. First, their proximity to warm, moist air from the Gulf of Mexico fill favor higher dew-points and greater instability. Second, the tornado season is a bit elongated here. While April into May have featured the most significant tornadoes in Dixie Alley, the late fall into winter months have also included several major tornado outbreaks. Finally, there may be at least some influence from tropical systems. While tropical storms and hurricanes often do produce tornadoes, it should be noted that most of these tornadoes are generally not significant. Eastern Nebraska into the Midwest also averages an elevated number of days per year with significant tornadoes. Here, while the tornado season typically peaks in June, at least some fall tornado events have spawned significant tornadoes this far north. In 2013, October 3rd-4th recorded six significant tornadoes from eastern Nebraska into Iowa, with the major tornado outbreak of November 17th featuring 32 significant tornadoes in the Midwest. Other noteworthy observations: Missouri is an interesting case. The western portion of the state is often considered to be in tornado alley and some maps will place southeastern Missouri in Dixie Alley. The state has seen plenty of significant and even violent tornadoes, with the Joplin tornado of 2011 being one of the more recent examples. However, a small section of central Missouri features a local minimum in terms of both tornadoes and significant tornadoes. One possible explanation can be their location being in a "dryslot" of sorts for tornadoes. For storm systems developing just east of the Rockies, the eastward extent of associated severe weather will often fall short of central Missouri. Likewise, systems developing in the lower Mississippi Valley often form a bit too far east to target central Missouri with the most tornadoes. West Virginia has less tornadoes than most states east of the Rockies. One factor that immediately comes to mind would be the population density and terrain, which may limit some tornado reports. However, their location along the Appalachians certainly plays a role in the lower frequency of tornadoes. The higher elevations will typically have less instability. Likewise, moisture pooling will typically favor higher dew-points west and east of the Appalachians, leaving West Virginia in another tornado dryslot. According to the NWS, West Virginia has no recorded EF/F-4 or 5 tornadoes. With that said, a long-track F-5 tornado in southeastern Ohio narrowly missed passing into West Virginia before lifting. Also, an F-4 tornado that dropped southeast of Pennslvania into Maryland also lifted shortly before it would have passed into West Virginia.

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New England Severe Bust? 7/15/2014

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. *

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Connecticut Snowfall Totals: Apr. 15-16, 2014

Here are some filtered snowfall maps 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. After early afternoon highs in the lower 60s across much of Connecticut on April 15th, a strong cold front moved through the area at night. Rain quickly changed to sleet and snow across the higher elevations of western Connecticut between 8 and 11 p.m. Although a changeover eventually took place from west to east across most of the state, the heaviest snow fell across western Connecticut. Snow ended before the pre-dawn hours on the 16th. Snowfall amounts of 1 to 2″ were common across northern Fairfield and Litchfield Counties. Although there was a gap in the data, it is possible that there were more reports of greater than 2″ across the Litchfield Hills. With this relatively small sample, the highest amounts were from Redding to Roxbury with 2 to 3″ or so. The radar image above left shows a band of heavy snow across northwestern Connecticut shortly after 12:30 a.m. on the 16th. As of 2 p.m. on April 16th, temperatures across the higher terrain in western Connecticut were only in the mid to upper 30s. As is often the case with early spring snowfalls, unseasonably cold air followed the snow. Here is a black and white version of the map: Click here for a complete list of snowfall totals used in these maps.

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May Outlook - Central/Eastern U.S.

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.

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Severe Weather Sunday

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.

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Severe Weather Possible This Weekend

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.

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April Outlook - Central/Eastern U.S.

A colder than average pattern may persist into April across the Great Lakes and Northeast. Based on the information I've been reviewing over the past several days, I have enough confidence to post a temperature outlook for the month of April. As I see it, below average temperatures will likely continue from the Great Lakes into interior New England and up toward Hudson Bay Canada. I expect a continuation of troughiness extending from southeast Canada into portions of the Northeast. While the heart of the Arctic air should remain well north of the U.S. border, there are other factors coming into play. With the current Great Lake ice coverage being significantly above average, it is going to take quite some time for the ice to melt and for lake-water temperatures to rebound. This means that any wind flow over the lakes will likely bring at least locally cooler temperatures, with transport from cold water to the adjacent land. For portions of the Deep South and especially into the southern Plains, I am expecting slightly above to moderately above average temperatures. A gradual re-emergence of a "Southeast Ridge" combined with a general storm track (with shifting entirely possible) through the Ohio Valley and Northeast, warmer air should be able to extend from the lower Mississippi Valley toward the lower Appalachians. Further west, the long-term drought over the central and southern Plains may persist, which is return would tend to allow for higher daytime temperatures than what is observed on average. Temperatures along the immediate Gulf Coast may be able to remain near average, as sea-surface temperatures in the area are running somewhat below average. Further speculation into the potential severe weather season leads me to believe that a relatively slow start to the season will continue. With that said, I can see a scenario where the region from the Ark-latex into Mississippi and Alabama has the opportunity for at least a few severe weather outbreaks into the month of April. This is supported by climatology as well, but places such as Kansas, Oklahoma and western Texas may not see a marked increase in severe weather activity until the second half of April. Severe weather forecasting is challenging, because all it takes is one major event to leave a mark. 2013 is a great example, as while the overall year saw below average severe storm reports, there were at least a few particularly damaging events. Other supporting references: The Euro weeklies and now the extended day Euro ensembles show the Northeastern U.S. trough relaxing north with some ridging (above average temperatures) across the Gulf States. (this is for the final days of March leading into the start of April)
The CFS up until late last week had a strong lean on well below average temperatures continuing across the Northeast. There has not been the greatest run-to-run continuity, but as of March 18th, there was at least moderate agreement with warming by the 2nd week of April.
The extended CMC ensembles do show some troughing in the East to start April, despite substantially above average heights in the final days of March in the same area.
The MJO is forecast by the Euro ensembles to move into Phase 2 and perhaps even Phase 3. The GFS ensembles move the MJO toward the edge of Phases 8 and 1, with the end of the curve clustering into Phase 1. More lean is placed on the Euro solution, however it should be noted that Phase 1 of the MJO favors below average temperatures in the eastern U.S., especially the Great Lakes. Phase 8 is closer to neutral/average. Phases 2 and 3 both match up more closely to Phase 1, with below average temperatures in the East and well below average temperatures from the Great Lakes into New England and southeastern Canada.
The 1993-94 seasonal analog has matched up in more ways than not to 2013-14. April 1994 saw a return to near and slightly above average temperatures in the East, with some stations reporting well above average temperatures in the Deep South and southern Plains.
March 1967 has several days that match up closely to the predictions for the latter half of March 2014. April 1967 featured considerably warmer than average temperatures across the southern Plains.
With all of the factors considered, I think this is a fair forecast to make at this point. Since we're talking about temperatures averaged out for the entire month of April, it's possible that an overall colder than average pattern lingers into the beginning of April before shifting. It is likely that even in such a pattern, we could see a couple of bouts of warmth. A good example is at the end of March. While as of March 18th there was a strong signal for an East Coast low around March 25th-26th, the consensus at this point is that some above average temperatures reach the Northeast once the low passes. On Saturday, I said this: There is a growing signal of a late-season winter event from March 25-26. However, given the overall troughy pattern expected to start April, there could be yet another winter event between April 1-5. I contemplated putting together a precipitation forecast, but rain/snowfall can vary substantially over a region, especially this time of the year. I think the pattern will remain active and perhaps some of this activity could help relax the drought in the Plains come later this spring. This was outlook was originally created on Saturday, March 15th, but I have added a few things here and there as new data as arrived. The maps and overall thinking have not changed. This is my first stab at a formal long-range forecast, so a lot will be learned by watching how the trends pan out.

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