AWUS01 KWNH 311125
FFGMPD
MAZ000-CTZ000-NYZ000-NJZ000-PAZ000-311630-

Mesoscale Precipitation Discussion 0831
NWS Weather Prediction Center College Park MD
725 AM EDT Thu Jul 31 2025

Areas affected...Northeast PA...Northern NJ...Southern Upstate
NY...Western CT...

Concerning...Heavy rainfall...Flash flooding possible

Valid 311130Z - 311630Z

SUMMARY...Early morning elevated shallow thunderstorms within
favorable steering/confluence axis may pose training/repeating
with totals up to 3". Given complex terrain/urban settings, there
is a non-zero potential for some localized lower-end flash
flooding this morning.

DISCUSSION...Regional RADAR and early morning GOES-E Visible
imagery show a broken line of shallow thunderstorms extending from
NE PA across southern NY just south of a low-level stratiform
layer associated with northerly 850mb flow from dying band of
showers across central Upstate NY into Interior New England. This
northerly flow intersects the nose of weak southerly return flow
with a slight upglide enhancement from the stationary front that
hugs the southern CT coast across N NJ into the Lehigh Valley.
The enhanced 900-850mb FGEN forcing with this enhanced theta-E air
from the Mid-Atlantic has sufficient 750-1000 J/kg of CAPE for
these shallow thunderstorms. Deep layer moisture is nearing 1.75"
with CIRA LPW of the surface to 850mb and 850mb-700mb layer
denoting the nature of the low-level loading of moisture in the
profile. While flux is not strong, some isallobaric enhancement
to the inflow may support enough into these shallower
thunderstorms for occasional 1.5"/hr rates.

This alone is not likely to induce flash flooding with exception
of the most prone urban locales if intersected. However, the
deeper layer flow, while weak, is confluent upstream over central
PA into NE PA becoming increasingly unidirectional to support
potential for some training/repeating. Overall instability and
weaker inflow/flux forcing is likely to limit overall
coverage/activity, but there are some growing signals to support a
spot or two of repeating cores for an isolated spot or two to
reach 3" totals over the next few hours. Proximity to complex
terrain over the Poconos/Catskills and terrain of N NJ along with
urban centers of S NY into W CT have some lower FFG values
(especially in the 1-3hr range) that may be exceeded. As a result
it is possible for a localized incident of flash flooding this
morning; though these cells will lay down the foundation for wet
grounds for later rounds this afternoon/evening.

Gallina

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

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

LAT...LON 42087362 42067278 41717251 41497283 41277340
40997421 40857556 41187607 41567566 41927451

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