Increasing Humidity in New England Late Week (6/23 - 6/27)
As a robust 500mb ridge builds across Canada, a closed low/trough will be held in place and meander around the Great Lakes / Southern Appalachian mountains through at least early next week. As of 00Z Tuesday (6/20), this upper level low is centered broadly over western Viginia and North Carolina. At the surface, a weak trough extends east-northeast from the outer banks of North Carolina, driving persistent onshore flow across southern New England. As the upper level low retrogrades between now and Friday, the surface pressure pattern will result in a more backed (southerly) low level fetch, quickly drawing moisture northward into the region.
Guidance differs somewhat in terms of when the richest moisture will arrive – it seems possible that it could be in place as early as Friday morning, or perhaps as late as Saturday morning. Once it is established, there is strong consistency that the column will moisten meaningfully (Precipitable Water magnitudes of 1.5" - 2") with surface dew points in the 65-72°F range.
Given the deeply moist atmosphere, and prospect of at least intermittent heating despite widespread cloud cover, surface based instability should develop each day this weekend, and likely into early next week as well. Guidance generally indicates MLCAPE values in the 500 - 1,500j/kg range, generally supportive of deep most convection. The proximate and fairly favorable position of the upper level trough, around which subtle shortwaves may rotate regularly, could also help to initiate rounds of convection each day. The prospect of organized severe thunderstorms remains unclear at this timeframe, but appears limited both due to the lack of stronger surface hearing/meager lapse rates resulting in narrow CAPE profiles, and a lack of organized/robust deep layer shear.
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.