Forecasts

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.

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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.

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.

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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.

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A synoptic pattern change will result in rapidly increasing humidity late this week across the northeast. Given the lack of rich surface moisture so far this season, the shift should be particularly noticeable across southern New England. High dewpoints and periodic chances for showers and thunderstorms are expected to last well into the medium range (through at least next Monday 6/26).

To the east of a dryline/Pacific front extending from Kay county southwestward to near Electra, TX, a very moist and strongly unstable environment is established across Oklahoma and north Texas.  Despite subtle synoptic scale forcing, numerous thunderstorms are expected to develop along the boundary and organize into multicell clusters and broken lines, supported by modest deep layer shear.  Favorable lapse rate profiles will initially support a threat of large hail near the boundary (I-44 corridor), transitioning to a threat of primarily damaging winds as storms aggregate and interact.

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A conditional risk of severe weather appears likely to evolve across portions of central Oklahoma Thursday evening.  As a shortwave trough emerges over a bulging dryline, sparsely scattered thunderstorms should initiate west of Highway 81 in the afternoon.  Shear vectors largely orthogonal to the dryline (particularly w/ southward extent) will favor supercell storm modes and increasing low level shear will support a tornado threat after 22-23Z.

Lapse rates are expected to be unimpressive by Great Plains standards (≤ 7C/km in the H7-H5 layer), but seasonally rich low-level moisture may support at least moderate instability.  The convective presentation could be bimodal – numerous storms in Kansas, and fewer, more intense storms in central Oklahoma later in the evening.

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A widespread, soaking spring rainfall is expected this weekend (4-29 & 4-30) across much of the northeast. A broad swath of rainfall totals exceeding 1" is likely. More focused areas of higher totals are also possible – perhaps as high as 2.5" - 3" in pockets stretching from the National Capitol region northeastward into southern Maine.

Tropical Storm Isaias will bring a range of weather conditions to New England beginning early Tuesday morning and lasting through the overnight hours.

The first significant winter weather event of the year will impact much of New England tomorrow, though some of the details still need to be ironed out. A relatively broad region of 6-12″ snowfall totals is expected to extend from the northern Worcester Hills across much of New Hampshire and into portions of Western Maine. Region-wide, snow will be very wet and heavy, increasing the risk of power outages where snowfall totals exceed 6″.

Summary: Warm temperatures, with highs rising into the mid-80s region wide, are expected today, and a few strong storms may pop across the north country and drift south during the late afternoon. During the day tomorrow, a backdoor cold front will usher in a fairly significant cool down, especially for coastal areas. Temperatures will drop rapidly during the midday hours from the upper 70s region-wide, to the low 60s at the coast by evening (with slightly more mild readings inland). A coastal-inland temperature gradient should persist into the Fourth of July holiday, with temperatures around 70F in the east and around 80F in the west.

There is a chance of isolated thunderstorms developing across New Hampshire, eastern Massachusetts, and southwestern Maine later today. Though overall coverage in this area is expected to be low, any storm that forms may become severe and produce large hail, damaging winds, and perhaps a brief tornado. Uncertainty is higher than usual for a day-of forecast, so be sure to stay alert for updates this afternoon and evening.

Strong to severe storms appear probably tomorrow afternoon and evening across much of New England. Though severe weather will likely be isolated, the most intense storms may produce hail up to 1.5" in diameter and wind gusts to 60mph, along with heavy downpours and lightning. The best chance of seeing a storm will be between 2PM and 6PM across Massachusetts, Connecticut, southern New Hampshire and northern Rhode Island.

Heavy snow will impact a broad corridor extending from central Pennsylvania east into southern New England Wednesday night and Thursday. Snowfall amounts around 1' should be common across southern upstate NY, northeast PA, and southern New England. 16" amounts are locally possible across Metrowest Boston, the eastern Berkshire slopes, and the Poconos/NY Capitol Region.