AWUS01 KWNH 290944
FFGMPD
MAZ000-NHZ000-RIZ000-VTZ000-CTZ000-NYZ000-NJZ000-291515-

Mesoscale Precipitation Discussion 0886
NWS Weather Prediction Center College Park MD
543 AM EDT Wed Jul 29 2026

Areas affected...Long Island, far northern NJ into eastern NY and
southern New England

Concerning...Heavy rainfall...Flash flooding likely

Valid 290942Z - 291515Z

Summary...Slow moving showers and thunderstorms will continue to
produce areas of flash flooding across eastern NY into southern
New England and Long Island this morning. Slow moving areas of
heavy rain are expected to produce an additional 3 to 5 inches of
rain in some locations through 15Z (11 AM EDT).

Discussion...Area radar imagery at 0915Z showed a slow moving
corridor of heavy rain impacting the Hudson Valley containing
observed hourly rainfall of 1-2 inches (locally higher). Farther
south, another axis of heavy rain was slowly pivoting east across
central Suffolk County into western CT. Despite weak instability
of about 500 J/kg or less, the region remained in a favorable
environment for heavy rain, positioned just ahead of a slow moving
low aloft with numerous mid-level vortices helping to focus
locally higher rainfall rates over inland locations. A surface/850
mb low has become rather well defined about 25 miles south of
Farmingdale, with 25-35 kt of southerly to south-southeasterly
925-850 mb flow transporting PWs of 1.7 to 2.0 inches across Long
Island into southwestern CT and eastern NY. Similarly oriented low
level and deeper layer steering flow has promoted training and
repeating rounds of heavy rain beneath diffluent and divergent
flow just east of the upper low over northeastern PA.

Short term forecasts from the RAP show the 850 mb low slowly
tracking north over the next 6 hours with the low level moisture
transport axis to its east pivoting eastward across Long Island
into southern New England. By 15Z, the low should be over
southwestern CT with low level southeasterly to easterly winds
across southern New England converging into a deformation zone
along the eastern NY border with CT/MA. It is here that the
highest additional rainfall totals may occur with slow moving
hourly rainfall values of 1 to 2+ inches over multiple hours.
While a single location may not see 1 to 2+ in/hr rainfall
continuously, the eastern NY into southwestern New England region
will be in a favorable location for periodic occurrences of higher
rainfall intensities. Terrain influences may factor into flash
flood severity. Given locally heavy rain across eastern NY into
portions of New England over the past 24-28 hours, flash flooding
could be locally significant this morning. Areas of flash flooding
will continue to be likely this morning with likely disruptions to
the morning commute and across locations of sensitive terrain.

Otto

ATTN...WFO...ALY...BGM...BOX...BTV...GYX...OKX...PHI...

ATTN...RFC...RHA...TAR...NWC...

LAT...LON 44117359 43967308 43607279 43027248 41957166
41337131 40937158 40667220 40467347 40657387
41177437 42237467 43407457 43937418

$$
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