Soaking Rain Expected This Weekend (4-29 & 4-30)
Synoptic Evolution
A favorable setup for widespread, locally heavy rainfall is evident over the next 36-60 hours across the northeastern United States. Three key upper level disturbances are noted in current (4/28-22Z) analysis – the first is rapidly moving southward into MN from southern Manitoba, the second is a digging, vigorous shortwave trough currently driving an evolving line of severe thunderstorms across southeastern TX, and the third is an amplifying shortwave trough driving south through Saskatchewan.
The two northern stream disturbances are modeled to interact and quickly amplify into a large closed upper level low centered over the Great Lakes during the day on Saturday. The southern stream shortwave is captured by the rapid flow around the aforementioned upper level low and should move rapidly northeastward. In response to this upper level evolution, two clear surface low pressure centers should establish themselves on Saturday – one in the Great Lakes, and a second over AL/GA. As the southern stream shortwave ejects rapidly to the northeast on Sunday, the southern surface low should deepen and absorb the northern low by 00Z Monday. This evolution triggers a significant mass response, drawing moist air up the Atlantic Seaboard and setting the stage for soaking rain across a broad region. Precipitable Water could rise 1-2 standard deviations above normal in New England Sunday night.
Projected 500mb Heights/Flow/Vorticity 00Z Monday
New England
Though persistent easterly flow is already established across New England and rain is close by (as far north as NYC), it's possible that much of Saturday stays relatively dry across the region. Guidance has trended drier in the last 24 hours, particularly near the coast. Model soundings indicate a lack of saturation below 700mb as late as 18Z, and given that the upper level disturbances are still quite far upstream at that time, confidence is increasing that much of Saturday will remain dry.
Periodic rain should overspread the region during the day on Sunday as the 500mb southern stream shortwave begins to approach from the south. Towards Sunday evening, the organizing low pressure system lifting north along the Hudson Valley will drag a warm front north across southern New England. Guidance develops a healthy 850mb jet ahead of this warm front, which should aid in rapidly transporting anomalously moist air northwestward, generating a broad region of moderate to heavy rain. With strong southeasterly flow, orographic enhancement could lead to maximized rainfall totals along the east-facing slopes of the White Mountains in eastern New Hampshire and western Maine. Both GEFS and EPS ensembles and more high-resolution guidance corroborate this conceptual model, placing the most impressive rainfall totals in orographically favored regions along the nose of the precipitable water plume.
EPS (top) / GEFS (bottom) – Total Precipitation through 00Z Tuesday
All told, rainfall totals exceeding 1" are likely for the entire Mid-Atlantic and Northeast region, with locally higher totals expected in a corridor from DC to downeast Maine, where a combination of anomalously high PW values and favorable dynamics will be co-located. Within this zone, totals near or over 3" are possible in orographically favored zones including central PA, and east-central NH/western ME.
Expected Precipitation
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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.