AWUS01 KWNH 091529
FFGMPD
VTZ000-NYZ000-NJZ000-PAZ000-092100-

Mesoscale Precipitation Discussion 0848
NWS Weather Prediction Center College Park MD
1129 AM EDT Fri Aug 09 2024

Areas affected...PA, northwestern NJ into Upstate NY and far
nortwestern VT

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

Valid 091526Z - 092100Z

SUMMARY...Post-T.C. Debby will maintain areas of flash flooding
from northern PA into NY, northwestern NJ and possibly far
northwestern VT. Rainfall rates of 1-2 in/hr (locally higher) and
additional totals of 3-5 inches are expected through 21Z. Some
flash flooding could be significant, especially with overlap of
urban locations and/or sensitive terrain.

DISCUSSION...Post-T.C. Debby was located over north-central PA as
of 15Z, moving quickly to the NE at just over 30 kt. An area of
heavy rain was associated with Debby's circulation center,
straddling the central NY/PA border, containing MRMS and gauge
derived rainfall rates of 1-2 in/hr. MLCAPE was limited to below
500 J/kg via the 15Z SPC mesoanalysis over central PA into central
NY but precipitable water values of 2.1 to 2.3 inches and strong
upper level divergence/diffluence were compensating for the lack
of instability. Farther east from east-central PA into the Hudson
Valley of NY, higher MLCAPE of 500-1000 J/kg was aiding in high
rain rates within south to north axes of training
showers/thunderstorms despite slightly weaker forcing aloft.

The surface low of Post-T.C. Debby is forecast to continue a swift northeastward movement toward the Tug Hill Plateau through 21Z. A
stripe of heavy/training rain will likely follow just west of the
path of the surface low where an axis of 2-4, locally up to 5
inches of rain is expected through 21Z with embedded rainfall
rates of 1-2 in/hr (locally higher). Farther east, areas of
training will be more transient but still noteworthy with embedded
rates of 1-2 in/hr and localized additional totals of 2-4 inches
through 21Z. Some of these areas of training could impact
sensitive terrain within the Catskills and Adirondacks or overlap
with urban areas, resulting in significant impacts.

Otto

ATTN...WFO...ALY...BGM...BTV...BUF...CTP...OKX...PHI...

ATTN...RFC...MARFC...NERFC...OHRFC...NWC...

LAT...LON 45207443 45197332 44487323 43517364 42417392
41867407 40777476 40307620 40417722 40977777
41357851 42147864 42657840 43437769 43697685
44457637 45127514
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