Subj : MESO: Mesoscale Discussion 1664
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Fri Jul 21 2023 16:20:33

ACUS11 KWNS 211620
SWOMCD
SPC MCD 211620=20
MAZ000-NHZ000-RIZ000-CTZ000-VTZ000-NYZ000-211745-

Mesoscale Discussion 1664
NWS Storm Prediction Center Norman OK
1120 AM CDT Fri Jul 21 2023

Areas affected...Parts of eastern NY...CT...central/western
MA...southern VT/NH

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

Valid 211620Z - 211745Z

Probability of Watch Issuance...40 percent

SUMMARY...Storm coverage will increase this afternoon, with some
threat for damaging wind, isolated hail, and possibly a tornado.
Watch issuance is possible.

DISCUSSION...In the wake of a weakening convective band now moving
across northern New England, showers have developed across parts of
western CT/MA, with convection recently becoming sufficiently deep
to support lightning across southwest CT. An increase in storm
coverage is expected into this afternoon from southeast NY into
parts of New England, as a jet maximum moves through the base of the
base of the upper-level trough, and related large-scale ascent
spreads over the region.=20

Diurnal heating of a moist low-level environment will support
continued destabilization this afternoon, with MLCAPE potentially
increasing to the 1000-1500 J/kg range. Meanwhile, moderate midlevel
flow will support effective shear in the 30-40 kt range, sufficient
for organized clusters and perhaps a few marginal supercells. Some
damaging-wind threat is expected to evolve as storms mature,
especially where stronger heating and steepening of low-level lapse
rates can occur this afternoon. Midlevel lapse rates are generally
weak across the region, but buoyancy will be sufficient to support
an isolated hail threat with any sustained supercells. Also, surface
winds may remain locally backed across parts of New England, to the
east of a surface trough across eastern NY. This may support
sufficient low-level shear/SRH for a brief tornado threat.=20

While the magnitude of the severe threat may remain somewhat limited
across the region, coverage of organized storms may become
sufficient for watch issuance this afternoon.

...Dean/Hart.. 07/21/2023

....Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj=
g!6oGdWZBl2cSlxwOENwgs3gvBB0e1e5cmb5LC7nx3QvFqFmMzH0DuFqpLUkUCkpzUSwb-8gpcl=
8FL1TQwrPNgY73zWow$  for graphic product...

ATTN...WFO...GYX...BOX...OKX...ALY...

LAT...LON   42117414 42767369 43137337 43207235 42967196 42677175
            42217173 41907182 41527211 41297302 41267361 41567393
            42117414=20


=3D =3D =3D
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