SPC MD 545

MD 0545 CONCERNING SEVERE POTENTIAL...WATCH POSSIBLE FOR SOUTHERN VIRGINIA AND NORTHERN NORTH CAROLINA

Mesoscale Discussion 0545
NWS Storm Prediction Center Norman OK
1057 AM CDT Sat Apr 22 2017

Areas affected...Southern Virginia and northern North Carolina

Concerning...Severe potential...Watch possible 

Valid 221557Z - 221800Z

Probability of Watch Issuance...40 percent

SUMMARY...Scattered thunderstorms are expected to develop early this
afternoon, and a few of the storms could produce damaging gusts and
marginally severe hail.  This area will continue to be monitored
through the afternoon, though the need for a watch is unclear.

DISCUSSION...Differential surface heating and a slow-moving front
across southern VA will likely focus thunderstorm initiation early
this afternoon.  Visible satellite imagery shows cumulus development
near the NC/VA border in a zone of differential heating, where
surface observations show temperatures warming into the mid-upper
70s with dewpoints in the mid 60s.  12z soundings revealed rather
modest midlevel lapse rates over this area, but continued surface
heating will boost MLCAPE into the 1000-1500 J/kg range, and a lack
of convective inhibition should allow scattered thunderstorm
development early this afternoon.  Some increase in storm coverage
may also be related to a band of ascent spreading east of the
southern Appalachians, in association with a weak convectively
enhanced midlevel trough.  

There is some enhancement to low-level shear on the immediate cool
side of the front sagging southward across southern VA, but wind
profiles will remain largely unidirectional with effective bulk
shear of 35-40 kt near and south of the front.  Thus, a few
organized storms/clusters, potentially with some supercell
structures, will pose a primary risk for damaging winds this
afternoon.  The scenario appears marginal for a severe thunderstorm
watch at this time, though the area will continue to be monitored.

..Thompson/Weiss.. 04/22/2017

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

ATTN...WFO...AKQ...RAH...RNK...

LAT...LON   36257840 36237946 36228031 36128082 36248132 36428162
            36758157 37228063 37387985 37237872 37207786 36937762
            36607762 36367784 36257840 

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