SPC MD 458

MD 0458 CONCERNING SEVERE POTENTIAL...WATCH POSSIBLE FOR PARTS OF CENTRAL AND EASTERN NORTH CAROLINA INTO CENTRAL AND EASTERN VIRGINIA

Mesoscale Discussion 0458
NWS Storm Prediction Center Norman OK
0459 AM CDT Thu Apr 06 2017

Areas affected...Parts of central and eastern North Carolina into
central and eastern Virginia

Concerning...Severe potential...Watch possible 

Valid 060959Z - 061130Z

Probability of Watch Issuance...60 percent

SUMMARY...Severe risk will gradually increase across central and
eastern portions of North Carolina and Virginia over the next few
hours, which may require watch issuance.

DISCUSSION...Latest radar loop shows some increase in both coverage
and intensity of convection across central North Carolina.  This is
occurring in response to strengthening ascent pivoting
north-northeastward across the Carolinas and Virginia as mid-level
short-wave troughing has rounded the base of the Midwestern low and
is now shifting rapidly toward the mid-Atlantic region.

The boundary-layer airmass across the NC/VA area remains
cool/saturated and slightly stable, with temperatures and dewpoints
in the upper 50s to low 60s.  However, with focused ascent near and
just ahead of the surface front yielding gradual cooling aloft,
steady weakening of the low-level inversion is expected to result in
near moist-adiabatic low-level profiles -- i.e. sufficient for
storms to eventually become at least near surface-based.  Above the
lower troposphere, mid-level cooling continues to gradually steepen
lapse rates, with the overall effect trending toward a thermodynamic
environment sufficient for vigorous storms.

Presuming storms can become near surface-based, severe risk --
including potential for a tornado or two -- will become increasingly
likely, as currently observed southeasterly surface winds veer and
increase rapidly with height, supportive of  updraft rotation. 
While the degree of risk remains a bit conditional/uncertain due to
the currently stable boundary layer, risk appears great enough to
warrant consideration of watch issuance over the next 1-2 hours.

..Goss.. 04/06/2017

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

ATTN...WFO...AKQ...MHX...LWX...RAH...ILM...RNK...

LAT...LON   35438002 36517981 37887892 38907726 38507591 37617596
            36557596 35777664 34827844 34887962 35438002 

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