ZCZC SPCSWOMCD ALL
ACUS11 KWNS 291721 
SPC MCD 291721 
PAZ000-MDZ000-VAZ000-WVZ000-291915-

Mesoscale Discussion 1388
NWS Storm Prediction Center Norman OK
1221 PM CDT Thu Jul 29 2021

Areas affected...Central/South-Central PA...Central MD...Extreme
Northern VA

Concerning...Severe potential...Watch possible 

Valid 291721Z - 291915Z

Probability of Watch Issuance...40 percent

SUMMARY...Increase in storm coverage and intensity possible, with a
corresponding threat for damaging wind gusts.

DISCUSSION...Convectively induced shortwave trough continues to
progress quickly eastward across the upper OH Valley. Strongest
forcing for ascent within this shortwave appears to be moving
through central and southwest PA now, demarcated by a line of
slightly higher reflectivity from roughly Clearfield County
southwestward through Greene County. Estimated motion with the
northern/central portion of the line is eastward at around 45 kt.
Southern portion of this line appears to be a bit slower, with storm
motion estimated to be east-southeastward at 35 kt. In both cases,
this area of stronger ascent will continue to move eastward across
PA and adjacent northern WV/western MD as the downstream air mass
destabilizes.

Abundant mid to upper level clouds are obscuring the low-level cloud
field as well as tempering heating. Even so, some cumulus can still
be seen across eastern areas of the region and temperatures have
risen into the upper 70s/low 80s. Based on modified RAP forecast
soundings, any remaining convective inhibition is minimal.
Consequently, an increase in storm coverage and intensity seems
possible as this shortwave continues eastward into this region over
the next hour or two. The overall environment supports bowing line
segments capable of damaging wind gusts with any more robust,
long-lived storms.

..Mosier/Hart.. 07/29/2021

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...CTP...LWX...

LAT...LON   40877782 40887711 40747663 40237645 39397690 39017767
            39737881 40547830 40877782 

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