SPC MD 1542

MD 1542 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR PORTIONS OF THE MID-ATLANTIC

Mesoscale Discussion 1542
NWS Storm Prediction Center Norman OK
0153 PM CDT Mon Aug 21 2017

Areas affected...Portions of the Mid-Atlantic

Concerning...Severe potential...Watch unlikely 

Valid 211853Z - 212100Z

Probability of Watch Issuance...20 percent

SUMMARY...Isolated to scattered thunderstorms will continue to
develop this afternoon from Virginia northward to Pennsylvania. The
strongest storms may be capable of isolated damaging winds and large
hail through early evening. However, the threat is expected to
remain sufficiently limited to preclude watch issuance.

DISCUSSION...Regional radar data depict blossoming convection across
the region this afternoon, aided by a weak impulse approaching the
northern Appalachians. 12Z regional soundings sampled poor mid-level
lapse rates, somewhat tempering convective vigor. Additionally,
visible satellite and radar data suggest a loss of insolation from
the ongoing solar eclipse is stunting destabilization of the
boundary layer. Nonetheless, with the return of stronger heating
later this afternoon, favorable low-level moisture should encourage
MLCAPE values upwards of 2500 J/kg. Weak southerly low-level flow
veering with height to modest mid-level westerlies (around 30-40 kt)
is offering around 30-35 kt of effective shear. In turn, a few
storms may exhibit sufficient updraft organization for isolated
instances of damaging winds and large hail. However, a lack of
greater coverage of severe convection will likely preclude watch
issuance.

..Picca/Grams.. 08/21/2017

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

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

LAT...LON   37937851 39587806 40557816 41557795 41717736 41627626
            41347593 39567614 38047648 37397715 37147755 37257822
            37937851 

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