A Few Storms North Today, Cooler for the Fourth (7-2-2020)
Analysis: First and foremost, today’s convective chances. As the upper level low that has dominated weather the last several days pulls away, a shortwave trough rippling through the flow aloft will kick off one or more bands of thunderstorms across southern Canada and northern New England this afternoon. A warm, moist environment at the surface, with middle 60s dew points extending north to the Canadian border, combined with ample diurnal heating should drive the development of some surface based instability across a broad region from the upper Hudson Valley east into Maine.
Northerly deep layer flow of 20-35kts juxtaposed over westerly to southwesterly surface winds will result in effective bulk shear magnitudes of 25-35kts region wide. With this degree of shear, a severe storm or two can not be entirely ruled out. CAM guidance indicates some risk of storms may extend into southern New England during the evening hours, but coverage is expected to be low.
As the boundary layer cools and the upper level disturbance begins to pull away late this evening, storms should dissipate by 03Z at the latest. In response to the shortwave, a surface low will organize in the Gulf of Maine overnight Thursday into Friday morning. In response to the surface pressure falls, boundary layer winds across much of New England become easterly and eventually northeasterly Friday morning. These winds will mark the arrival of a strong backdoor cold front, which should arrive in Boston, Lawrence and Concord around 13Z, in Worcester around 14:30Z, in the Pioneer Valley around 16Z, and in the Berkshires around 20Z. As the front moves through, temperatures in the upper 70s and low 80s should cool into the 60s in most places, though it may remain a bit warmer in the more protected valleys.
Northerly-to-northeasterly flow will likely maintain itself at the surface through the Independence Day holiday. With the strong July sun angle, the temperatures in the cool sector should moderate at least somewhat on Saturday, but with the breeze off the North Atlantic, daytime highs will probably struggle to exceed 72-74F at the immediate coast, and 80F inland, well below average for midsummer.
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.