Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Fri Jul 14 2023 18:41:45

AWUS01 KWNH 141841
FFGMPD
MAZ000-NHZ000-VTZ000-CTZ000-NYZ000-NJZ000-PAZ000-150040-

Mesoscale Precipitation Discussion 0727
NWS Weather Prediction Center College Park MD
241 PM EDT Fri Jul 14 2023

Areas affected...Interior Northeast...New England

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

Valid 141840Z - 150040Z

Summary...Thunderstorms are beginning to erupt across portions of
the Interior Northeast and New England along a stationary front.
Bouts of high rainfall rates upwards of 2-2.5"/hr will lead to
some instances of flash flooding this afternoon given the
compromised soils across the Northeast and New England.

Discussion...Radar and day cloud phase imagery across the East
Coast depicts convective initiation is underway between KENX and
KBGM, in the vicinity of a stalled cold front. Thunderstorm
coverage is expected to increase over the next several hours as
convergence along the front interacts with several weak shortwaves
and some coupled jet forcing. Filtered insolation combined with
upper 60's-low 70's dewpoints supports 500-1500 J/Kg MLCAPE across
the region, albeit with some CIN in the wake of this morning's
storms. An abundance of tropical air remains across the region
with PWATs ranging from 1.2-1.9" (hovering in the 75th-90th
percentile range), and deep warm cloud layers hovering around
3-4000 meters. Meanwhile, enhanced southwesterly flow is forecast
to yield 25-30 kts of effective bulk shear which will encourage
some organized multi-cell clusters. In all, this environment
should support efficient warm rain production going into the
afternoon, with rates upwards of 2-2.5"/hr possible.

As storms build, bulk shear vectors oriented acutely to
quasi-parallel to the front and upper-forcing are expected to
support some repeat instances of thunderstorms, with rainfall
totals upwards of 2-4" possible through 0z tonight. This is
expected to lead to flash flooding given the degree of compromised
soils and FFGs (.25-1.25"/hr 1 HR FFGs) atop the region in light
of the very heavy rains over the last week. The 12Z HREF suggests
enhanced probabilities of 6 HR QPF exceeding the 5-10 year ARI
across the region (45-35%, respectively), with a signal for 100
year ARI exceedance also noted across portions of eastern PA
through NH (5-15%). Given the degree of the previous rainfall,
current signal from the HREF, and urban coverage, instances of
flash flooding are considered likely through tonight.

Asherman

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!9L2V5-KZ4OTK0OEy9QZ6l-yLS-MIAdQx7fRM0_mouMgAhpzkaOHUwb-hCPl2IjXJM54s=
H8z3HYxGbmcBmFnMMsZYU10$  for graphic product...

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

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

LAT...LON   44857207 43827125 41997226 40277432 40527542=20
            41267608 41817611 42537570 43297449 44107312=20
=20=20=20=20=20=20=20=20=20=20=20=20

=3D =3D =3D
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