Strong Storms Probable in New England This Afternoon (6-28-2020)
As of 04Z Sunday, mesoanalysis reveals a subtle shortwave currently centered near KAPX (Gaylord, MI), oscillating southeastward around a closed 500mb low centered over southeastern Canada. Given the modest belt of H5 west-north-westerlies south of the low, this feature should approach New England around 18-21Z today, setting the stage for one or more rounds of thunderstorm development.
At the surface, a relatively rich pool of moisture is present over and especially just off of the mid-Atlantic coast, an airmass that should translate northward into the morning hours. The 28.00Z OKX sounding revealed an impressively moist low level environment with small dew point depressions from the surface to 600mb and an attendant PW value of 1.77". Additionally, surface dew points of 66-68F, moister than the 00Z high resolution guidance mean, are being observed as far north as KPYM and KBDL, indicating, in conjunction with the RAOB from OKX, that the low level environment will likely be at least as moist as the mean of the guidance.
In conjunction with amply insolation and sufficient mid-level lapse rates, the moist boundary layer should yield a broad, moderately unstable environment characterized by MLCAPE of 1500-2000j/kg. Though sampled lapse rates at 00Z were not impressive, there may be some improvement as the 500mb temperatures cool by 2-3C tomorrow. All told, I am confident in sufficient environmental destabilization to support robust thunderstorms during the afternoon and evening.
As mentioned earlier in the discussions, winds aloft will not be particularly strong, and deep layer shear will be meager accordingly, likely only on the order of 25-30kts in the effective layer. With that said, the wind profile is unidirectional and fairly well-organized above 2km, so some storm organization, especially into loose clusters and transient bowing segments, is not out of the question.
With sufficient shear for loose storm organization and large buoyancy (by New England standards), hail up to 1.5" in diameter should be a threat with the most intense updrafts, and idea supported by numerous severe hail analogs on model soundings across the region. Strong to locally damaging winds will also likely be realized given DCAPE >= 700j/kg as inverted-V profiles develop towards peak heating.
Taking a peek at the latest HREF - convection-allowing guidance indicates the greatest concentration of robust updrafts should materialize along an arc from east-central New Hampshire southward across Massachusetts and Connecticut during the late afternoon hours. Given the expectation of weaker deep layer flow and buoyancy across northern New England, I think storms may be a bit weaker in that region despite cooler temperatures aloft.
The most probably scenario appears to be the evolution of one or more bands of storms, with strong to severe cells embedded across central and particularly Southern New England, perhaps extending westward into portions of the lower Hudson Valley. The chance for storms should maximize between 18Z and 22Z, perhaps lingering a bit longer in the easternmost counties.
More Forecasts
A Tornado Outbreak is Possible on Monday in Oklahoma & Kansas
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As of this evening, a broad corridor of conditional significant severe weather potential appears likely to evolve across Kansas, Oklahoma, and perhaps extreme northern Texas tomorrow afternoon and evening. If storms are able to form along the dry line between 3pm and 8pm, the ambient environment will be supportive of strong tornadoes, giant hail, and eventually upscale growth with an attendant damaging wind threat.
People in areas at risk for severe weather should monitor trusted sources tomorrow for additional information.
Synoptic Storm Expected Early Next Week (12-18-23)
Synopsis: A large low pressure system will bring active weather to much of the eastern seaboard, with a focus in New England, late this weekend into early next week. As the low moves northward from its current position in the northern Gulf of Mexico, a favorable upper-level pattern evolution should allow the system to deepen rapidly to near 980mb at 40°N. Rapid pressure falls should result in a large mass response/impressive low-level jet evolution, increasing the risk for damaging wind gusts and drawing a large plume of moisture northward. Near the surface low, a 10-18 hour period of steady to heavy rain can be expected, with a shorter window of potentially damaging winds along the NewEngland coast during the day on Monday.
Severe Storms in New England Thursday (7/27)
Thunderstorms are expected to develop across southern New Hampshire, the Hudson Valley, and perhaps northeast Pennsylvania, and move southeast with time through a favorable environment. Damaging winds, flash flooding, and tornadoes will all be possible with the most intense storms. A particularly favorable environment for tornadoes could evolve across northern MA/southern NH during the afternoon, where strong low-level shear will be co-located with substantial instability.
Strong Storms & Flooding Possible Friday (7-14)
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In a deeply moist and unstable airmass, subtle disturbances aloft should trigger waves of thunderstorms across New England and New York on Friday. A focused corridor of severe thunderstorm potential could emerge across portions of downstate NY and southern New England.