MD 1282 CONCERNING SEVERE POTENTIAL…SEVERE THUNDERSTORM WATCH LIKELY FOR PORTIONS OF SC…NC…VA…THE EASTERN WV PANHANDLE…MD…DC…DE…CENTRAL/EASTERN PA…NJ…AND SOUTHERN/WESTERN NY
Mesoscale Discussion 1282
NWS Storm Prediction Center Norman OK
1136 AM CDT Mon Jun 26 2023
Areas affected...Portions of SC...NC...VA...the eastern WV
Panhandle...MD...DC...DE...central/eastern PA...NJ...and
southern/western NY
Concerning...Severe potential...Severe Thunderstorm Watch likely
Valid 261636Z - 261900Z
Probability of Watch Issuance...95 percent
SUMMARY...Scattered to numerous damaging winds and large hail will
become an increasing concern this afternoon. Multiple Severe
Thunderstorm Watches will likely be needed to address this severe
threat over the next couple of hours.
DISCUSSION...16Z surface analysis shows a surface low centered over
Lower MI with a cold front extending southward from this low across
the OH Valley. A weak pre-frontal trough is present along/near the
Blue Ridge Mountains into western/central NC. Much of the
Mid-Atlantic still has considerable cloudiness early this afternoon,
which will hamper diurnal heating to some extent. The clouds across
central/eastern VA into MD is associated with a remnant
MCV/mid-level vorticity maximum, with weak subsidence noted behind
it. Better heating will continue across southwest VA into western NC
and much of SC, where less cloud cover exists. Still, a moist
low-level airmass is present across the Mid-Atlantic/Carolinas, with
generally mid 60s to low 70s surface dewpoints in place. Continued
heating of this airmass will likely promote around 1000-2500 J/kg of
MLCAPE by mid afternoon, with greater instability expected in the
Carolinas where mid-level lapse rates are steepened.
Current expectations are for thunderstorms to continue developing
across the higher terrain of the Appalachians, and perhaps the
surface lee trough, as weak ascent associated with an upper
trough/low centered over the Great Lakes overspreads the
Mid-Atlantic. Convection is already ongoing across parts of PA and
western/southern NY, with a measured severe gust recently recorded
at KDKK in far western NY. Weaker forcing across the Carolinas casts
some uncertainty regarding overall thunderstorm coverage with
southward extent. Better mid-level flow around the base of the upper
trough/low should tend to remain over the Carolinas through the day.
30-40 kt of deep-layer shear across NC/SC will support some threat
for supercells and large hail with initial development.
Across the Mid-Atlantic, effective bulk shear should be somewhat
weaker, generally in the 20-30 kt range. Mainly multicells/clusters
should be the dominant mode across this region, with perhaps
isolated/marginal supercells possible. Wherever enough clearing can
occur to promote steep low-level lapse rates, a threat for damaging
downdraft winds will exist. Multiple corridors of potentially
greater coverage of scattered to numerous damaging gusts are evident
based on observational and short-term guidance trends. One such
possible corridor is across eastern PA into NJ. Multiple Severe
Thunderstorm Watches will likely be needed this afternoon across the
Mid-Atlantic and Carolinas to address the increasing threat for
damaging winds and severe hail.
..Gleason/Grams.. 06/26/2023
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...OKX...ALY...PHI...BGM...AKQ...BUF...CTP...LWX...
RAH...ILM...RNK...CAE...GSP...
LAT...LON 33798208 34798225 36388125 38547930 40737817 42097914
42857863 43337753 43447664 42867540 42117436 41567404
40877377 39577418 38957477 38297507 37287569 36357710
34787913 33498090 33338151 33798208
