SPC MD 503



MD 0503 CONCERNING SEVERE POTENTIAL…WATCH UNLIKELY FOR PORTIONS OF NORTHERN AND NORTHEAST VIRGINIA…WASHINGTON D.C….EASTERN MARYLAND

MD 0503 Image

Mesoscale Discussion 0503
NWS Storm Prediction Center Norman OK
0228 PM CDT Thu May 02 2019

Areas affected...Portions of northern and northeast
Virginia...Washington D.C....eastern Maryland

Concerning...Severe potential...Watch unlikely 

Valid 021928Z - 022130Z

Probability of Watch Issuance...20 percent

SUMMARY...Current multicellular clusters, along with anticipated
downstream development, pose an isolated damaging wind threat
through the mid-late afternoon hours. The isolated extent of the
severe threat precludes a WW issuance at this time.

DISCUSSION...Convective development (including multicellular
clusters), is underway across the easternmost fringes of the higher
terrain associated with the Appalachians, along the nose of a
surface thermal ridge. Aloft, large scale mid-level ridging is in
place, suggesting that convective development has mainly been
supported by vigorous boundary layer mixing (with up to 8.5 C/km
sfc-3km AGL lapse rates present as suggested by 19Z RAP forecast
soundings), and orographic lift. 

Adequate buoyancy (i.e. 500-1000 J/kg MLCAPE) and effective bulk
shear (30-40 knots of mainly speed shear in the 850-700 mb layer) is
in place. Nonetheless, the lack of stronger synoptic deep-layer
ascent, directional deep-layer shear, and negligible low-level
shear, all suggest that storms should be organized for only brief
periods of time, long enough to perhaps support water loaded
downdrafts capably of producing damaging wind gusts. Given the
brevity and isolated nature of the severe threat, a WW issuance is
not anticipated at this time.

..Squitieri/Hart.. 05/02/2019

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

ATTN...WFO...PHI...AKQ...LWX...RNK...

LAT...LON   37717951 38567864 39457743 39487697 39697614 39327571
            38547617 37857820 37717951 

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