SPC MD 439

[NorthGeorgiaWX]

MD 0439 CONCERNING SEVERE POTENTIAL...SEVERE THUNDERSTORM WATCH LIKELY FOR PORTIONS OF WEST VIRGINIA...VIRGINIA...MARYLAND...AND DELAWARE

Mesoscale Discussion 0439
NWS Storm Prediction Center Norman OK
1203 PM CDT Mon Apr 15 2024

Areas affected...portions of West
Virginia...Virginia...Maryland...and Delaware

Concerning...Severe potential...Severe Thunderstorm Watch likely 

Valid 151703Z - 151900Z

Probability of Watch Issuance...95 percent

SUMMARY...Thunderstorm activity is expected to increase by 3-4pm
EDT. Damaging gusts to 60-70 mph and large hail to 1.5 inches in
diameter will be possible through early evening.

DISCUSSION...Gradual destabilization is occurring from west to east
early this afternoon across the MCD region. Increasing cumulus
development is noted over the past hour across the higher terrain of
West Virginia into northern Virginia as temperatures have warmed
into the 70s to low 80s. The 12z MPAS-HT high-res guidance appears
to have the best handle on morning convection across the region, and
in the expected convective evolution through early evening. Based on
this guidance, and current observed trends, thunderstorm activity is
expected to increase by 19-20z/3-4pm EDT near/south of a residual
frontal boundary draped west to east across the region. This
development will be aided by continued heating/destabilization,
increasing midlevel moisture and a very steep low and midlevel lapse
rate environment (midlevel lapse rates around 8 C/km with southward
extent across VA).

While low-level winds will remain light, a belt of 30-40 kt midlevel
flow will foster effective shear magnitudes suitable for organized
convection. Initial cellular activity will pose a risk for large
hail and strong gusts. Meanwhile, a deeply mixed boundary-layer with
inverted-v sub-cloud thermodynamic profiles suggest strong outflow
winds will occur with this activity and clustering is likely to
occur via outflow interactions. A damaging wind threat will increase
with southeastward extent across Virginia toward the Chesapeake Bay
vicinity where steep low-level lapse rates and DCAPE over 1000 J/kg
will be focused.

A severe thunderstorm watch will likely be needed for portions of
the MCD vicinity by 18-19z.

..Leitman/Smith.. 04/15/2024

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

ATTN...WFO...PHI...AKQ...LWX...RNK...PBZ...RLX...

LAT...LON   39387892 39417647 39277553 38927496 38717477 38077471
            36797576 36617617 36577708 36797916 36977959 37708109
            38248124 38618114 38868058 39157996 39387892 

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