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Quincy

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  1. Quincy
    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.

  2. Quincy
    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.

  3. Quincy
    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.

  4. Quincy
    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.

  5. 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.

  6. Quincy
    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.

  7. 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.

  8. Quincy
    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.
  9. 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.

  10. Quincy
    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

  11. 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.
  12. 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, 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.

  13. Quincy
    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.
  14. 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.
    *
  15. Quincy
    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.
  16. 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.

  17. 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.
  18. Quincy
    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.
  19. Quincy
    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.
    Flurries and light snow moved into Connecticut around daybreak on February 18th as low pressure formed east of New Jersey. The snow moved east and began to develop into a steadier area of snow across New Haven and Middlesex Counties. As a compact, but potent low pressure system developed over Long Island, a band of heavy snow formed near and just east of I-91 from the New Haven area up to the Massachusetts border. Snowfall rates of 1 to 2 inches per hour were observed in many locations.
    The snow changed to a bit of rain across extreme southeastern Connecticut before ending. Some mixed snow and ice pellets were also noted near the shoreline from New Haven and points east during the afternoon.
    Snow ended in northeastern Connecticut by late afternoon. A general 3 to 6 inch snowfall was observed for the eastern half of the state. Less snow fell in western Connecticut and across southeastern sections. There was a narrow band of 6"+, extending from near Meriden, northeastward up to Somers.
    Here in New Haven, the total snowfall was 4.1" Toward the end of the storm, 1.2" of snow fell in just one hour from noon to 1 p.m. The precipitation ended as snow pellets shortly after 1 p.m.
    Here is a black and white version of the map:

  20. Quincy
    Here are some 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.
    Light snow overspread the state from southwest to northeast shortly after midnight on February 5th. This was ahead of a low pressure system that was moving into the eastern Ohio Valley. The snow quickly became heavy at times around daybreak, with snowfall rates of 1 to 3 inches per hour. A gradual change to sleet and freezing rain also took place through the morning from south to north. Warmer air flooded in aloft, although there was a cold layer that was very slow to erode near the surface.
    Around midday, there was a break in the action with just some spotty drizzle and light mixed precipitation. The shoreline and parts of eastern Connecticut did briefly rise above freezing. A glaze of ice was observed between I-95 and I-84, with the most significant icing across the climatologically favored sheltered areas of Fairfield and New Haven Counties in the vicinity of Route 15. An inch of sleet was reported in many areas and the size and intensity of sleet that I observed was the most impressive I can ever recall.
    During the afternoon, colder air moved in as a secondary low developed just south of Long Island. Precipitation ended as a few snow showers on the night of the 5th, with a few flurries into the early morning hours on the 6th across eastern Connecticut.
    Snowfall totals between 8 and 10 inches were common. Somewhat less snow fell along the immediate shoreline and in eastern Connecticut. The higher totals were around a foot across central and northwest portions of the state.
    Here is a black and white version of the map with filtered reports:

  21. Quincy
    Here are some 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.
    Flurries began to move into Connecticut shortly after daybreak on January 21st. The snow gradually overspread the state from southwest to northeast and light accumulations were noted across southwestern Connecticut by midday.
    As an area of low pressure developed off the mid-Atlantic coast during the afternoon, a band of heavy snow developed along a SW to NE axis from Philadelphia into Long Island. This band of heavy snow lifted northward and made it about as far as I-84 in Connecticut. Drier air won out on the northwest side of the storm as snowfall totals across Litchfield and Hartford Counties were generally lower than forecast. Areas southeast of the I-95 corridor from Bridgeport to the Rhode Island border also saw less snow, as the heaviest band of snow lifted inland.
    The below radar image demonstrates where the heavy band of snow maxed out. Most of the higher-end snowfall totals were observed in the green shading:

    With low pressure moving eastward early on January 22nd, snow tapered off from west to east during the pre-dawn hours. By daybreak, the accumulating snow was over and air temperatures had dropped into the single digits above, and in some cases, below zero.
    Liquid-to-snow ratios with this storm were fairly impressive. Ratios were commonly in the 20-25:1 range, although some locations observed even greater ratios. Here is a sampling of some of the ratios that were reported:
    North Grosvenordale: 30:1, Oakdale: 26:1, Stratford, 26:1, Portland: 20:1, Essex: 19:1, West Hartford: 18:1.
    The result was a very light and fluffy snow that was very easy to move and shovel. The fluffy nature of the snow also resulted in settling and compaction.
    Here in New Haven, the final snowfall was 8.0". Most of the snow fell before 10 p.m. Snowfall rates averaged around 1" per hour from about 4 p.m. to 7 p.m. when the band of heavy snow moved through the area. The depth of snow as of the afternoon on January 22nd was approximately 6".
    Liquid equivalent precipitation amounts were generally less than modeled across Connecticut. Common values were near 0.2 to 0.3", with lower amounts across north-central and northwestern parts of the state. The SREF data did an excellent job at nailing down a region for heavy snow from the northern half of New Jersey into southwestern Connecticut. It was here that the model showed strong frontogenetical forcing and was eluding to a snowfall maxima. With that said, the SREF and many other models were too generous on the northwest side of the storm for precipitation amounts.
    Here is a black and white version of the map with filtered reports:

  22. 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.

  23. Quincy
    Here are some 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. Blowing and drifting snow made it difficult to obtain an accurate measurement. Some towns had multiple reports and totals that appeared to be too high based off of surrounding reports were not used.
    Some warm-advection snow lifted into Connecticut as early as the night of January 1st, the vast majority of the accumulating snow began on January 2nd. From morning through afternoon, flurries and periods of light snow moved from south to north across the state. By afternoon, some areas, mainly across the northern half of the state, reported an inch or two of snowfall. The 12z sounding from January 2nd at OKX indicated somewhat of a dry layer aloft, while ALY was more saturated. The best snows early on were measured from central New York into portions of interior Massachusetts.
    During the evening, low pressure eventually developed off of the mid-Atlantic coast and an area of snow filled in across Connecticut. It was from about 9 p.m. to 4 a.m. that the heaviest snow fell. The bands of heaviest snow wound up remaining south of Connecticut and there were even more impressive snowfall totals across eastern Massachusetts. There, ocean-enhancement was a key role in significantly higher snowfall amounts.
    In Connecticut, accumulating snow ended by mid-morning on January 3rd, with most areas receiving anywhere from 4 to 7 inches of snow. There was a narrow band of 7 to 7.5 inches across the northern part of the state, where additional snow during the beginning of the event increased overall totals. Close to the coast, there were also a few totals of 7 to 7.5 inches, where some towns were grazed by heavier snow toward the end of the event.
    While there were a few snowfall totals reported in the range of 8 to 9+ inches, those did not line up with other totals in the same or neighboring towns. Strong winds caused blowing and drifting snow, which was the most likely cause for the totals that were assumed to be erroneously high.
    One variable that was generally missed by the computer forecast models was lower liquid-to-snow ratios. While these ratios are generally close to 10:1, model forecasts predicted anywhere from 15-20:1 ratios, or even higher. If higher ratios had been observed, snowfall totals across Connecticut would have been higher. In the end, ratios were fairly close to 10:1.
    It was quite cold during the storm with temperatures falling into the lower 10s and single digits by the morning of January 3rd. Although there is a loose correlation between surface temperatures and snow ratios (colder yielding higher ratios), it was the snow growth above the surface that did not promote higher ratios. Surface temperatures alone have no impact on snow ratios, unless the temperatures are near or above freezing, then they can actually lower the ratios.
    If any amounts you reported conflict with these amounts, please comment back with your total(s).
    Here is an alternate black and white version of the map:

  24. Quincy
    Here are some 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.
    A clipper system that gave way to a coastal low just south of Long Island resulted in generally 2 to 4 inches of snow across the state. There were a few localized totals of just over 4 inches, but there were no reports over 5.0 inches. The highest totals were across the higher terrain, where some modest orographic enhancement and/or higher snowfall ratios may have come into play. There was a "snow hole" in southeastern Connecticut where generally 2 inches or less was measured. A few of the higher resolution models hinted at this area of localized lower amounts, but most data pinned that area further north.
    Snow flurries developed around daybreak on December 17th and periods of light snow continued through midday. After a break in the action, an area of moderate to locally heavy snow formed by mid-afternoon as low pressure intensified just to the south. Snowfall rates approached one inch per hour for a time. Some warmer air worked north and there was a change to sleet and freezing rain cross portions of lower Fairfield County. Snow tapered to flurries during the evening hours.
    If any amounts you reported conflict with these amounts, please comment back with your total(s).
    Here is an alternate black and white version of the map:

  25. 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.

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