Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Fri Jul 07 2023 15:11:36

AWUS01 KWNH 071511
FFGMPD
VTZ000-NYZ000-PAZ000-072110-

Mesoscale Precipitation Discussion 0652
NWS Weather Prediction Center College Park MD
1109 AM EDT Fri Jul 07 2023

Areas affected...Interior Northeast

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

Valid 071510Z - 072110Z

SUMMARY...Blossoming thunderstorms with slow storm motions and
hourly rainfall rates over 2"/hr will likely produce areas of
flash flooding, especially in areas with more sensitive soils.

DISCUSSION...A broad 250-500mb trough axis over southeast Canada
is co-located just west of a 250mb jet streak over Quebec. The
diffluent right-entrance region is positioned over the Northeast
at the same time as a frontal system approaches from western
NY/PA. Strong surface based heating is ongoing from central PA on
north and east through the Finger Lakes of NY, the Catskills and
Adirondacks, and up towards Lake Champlain. The atmosphere is
growing more primed to support excessive rainfall rates with
increasing PWATs (1.5-1.75" available) and MLCAPE that is forecast
to reach 1,000-1,500 J/kg later this afternoon.

The available moisture and storm motions are supportive for flash
flooding potential. RAP guidance suggests 1000-500mb RH values
will range between 80-90% in some parts of the area with warm
cloud layers as deep as 11-12kft. Dew points are already in the
upper 60s and low 70s with any lingering CIN quickly eroding.
Visible satellite shows storms have already begun to take shape
and more will develop over the next hour or two. Storm motions
will be on the slower side with sfc-3km winds generally <10 kts.
There are stronger winds above 3km, but this is also fostering a
more sheared environment as latest RAP guidance also shows 25-30
kts worth of effective bulk shear this afternoon.

The region has dealt with rounds of heavy rain in recent weeks,
particularly in northern PA, south of I-90 in NY, and as far north
as the NY/Quebec border. Soils are a little more susceptible to
flash flooding, highlighted by 1-hr FFGs <1.5" in most of these
aforementioned areas. Given the favorable atmospheric parameters
and antecedent soil moisture present, flash flooding is likely to
occur this afternoon. Areas with the most saturated/sensitive
soils, as well as more urbanized settings and poor drainage areas
are most vulnerable to flash flooding.

Mullinax

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!_jf63kVbqE_ql2njkSEHbFR2M15BpguOAtSTzfwCoRmk9_nuNzp7ZUJ_yeXnqw7BzgNQ=
IBiFyfthq1Tcx4lpwzKZ6aE$  for graphic product...

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

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

LAT...LON   45057416 45027318 44597303 43757334 42547415=20
            41357523 40707629 40817887 41417954 42907790=20
            44337620 44917525=20

=3D =3D =3D
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