Subj : MESO: Mesoscale Discussion 1521
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Thu Jul 13 2023 18:37:30

ACUS11 KWNS 131837
SWOMCD
SPC MCD 131836=20
PAZ000-MDZ000-DCZ000-VAZ000-WVZ000-132100-

Mesoscale Discussion 1521
NWS Storm Prediction Center Norman OK
0136 PM CDT Thu Jul 13 2023

Areas affected...Portions of eastern WV...VA...DC...western/central
MD...and central/eastern PA

Concerning...Severe potential...Watch possible=20

Valid 131836Z - 132100Z

Probability of Watch Issuance...40 percent

SUMMARY...Some threat for damaging winds and hail may exist as
thunderstorms move eastward this afternoon. The need for a watch
remains unclear, but trends will be monitored.

DISCUSSION...Scattered thunderstorms have developed this afternoon
across parts of the central Appalachians. More isolated activity is
attempting to deepen across parts of north-central into northeastern
PA, closer to the upper trough over NY and southern Quebec. A
surface lee trough is present along/east of the Appalachians/Blue
Ridge Mountains, with ample daytime heating acting to steepen
low-level lapse rates. Latest mesoanalysis shows a relative minimum
in instability along/east of the lee trough across parts of
central/eastern VA into central MD and eastern PA. This area appears
to have shallower low-level moisture based on area 12Z soundings,
and some lingering MLCIN.

Still, various RAP/NAM forecast soundings across this region suggest
that a well mixed boundary layer will support at least an isolated
damaging wind threat with any convection that can spread eastward
off the higher terrain this afternoon and evening. Around 25-35 kt
of deep-layer shear should also foster some thunderstorm
organization, with multicells to marginal supercells possible. Some
hail may occur with the strongest cores. With better large-scale
ascent focused farther north across NY and New England, overall
thunderstorm coverage remains uncertain. The need for a Severe
Thunderstorm Watch this afternoon is also unclear, but observational
trends will be closely monitored.

...Gleason/Bunting.. 07/13/2023

....Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj=
g!7FFe1MZqPg2KJuFiMktfJt6_qFz1_kT75eFFiYeNAQDxekOufNpKnQZczMF7A6ObxNdUho-vA=
nzpb17j58F_JKBD0VI$  for graphic product...

ATTN...WFO...PHI...BGM...AKQ...CTP...LWX...RNK...

LAT...LON   36898068 39057921 39887863 41777665 41747536 40947513
            38517672 37207843 36657958 36898068=20


=3D =3D =3D
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