Mesoscale Discussion 0698
NWS Storm Prediction Center Norman OK
0347 PM CDT Thu May 11 2017
Areas affected...Portions of eastern KY...northeastern TN...southern
WV...southern VA...NC
Concerning...Severe potential...Watch possible
Valid 112047Z - 112315Z
Probability of Watch Issuance...40 percent
SUMMARY...At least isolated severe risk will extend from portions of
eastern KY east-southeastward to eastern NC into the evening hours.
It is unclear whether severe coverage will be sufficient for Watch
issuance, though environmental/convective trends will be monitored
for possible Severe Thunderstorm Watch issuance.
DISCUSSION...Clusters of thunderstorms have developed from parts of
central KY to southern WV and will continue tracking
east-southeastward into the evening hours. This activity lies within
the warm side of a baroclinic zone extending from KY through
northeastern NC. Some of this activity has shown indications of
localized upscale growth, which could subsequently support a
downstream, greater risk for damaging winds amid pre-convective
diurnally steepened low-level lapse rates.
Ahead of the KY/WV convection, additional convective development may
occur. This would especially be the case in proximity to a segment
of the baroclinic zone from southern VA into
northern/central/eastern NC -- where baroclinic circulations are
enhanced in association with more substantial contrasts in theta-e.
Cumulus development is already noted in this regime, where greater
surface heating (temperatures into the lower 80s) has boosted
low-level lapse rates.
All of the aforementioned convection will spread east-southeastward
and perhaps southeastward toward/across the Appalachians, Piedmont
region, and coastal plain into the evening hours. With around
500-1250 J/kg of MLCAPE and 40-55 kt of effective shear, continued
robust and somewhat organized convective structures may evolve.
Isolated damaging wind gusts will remain possible (as previously
described), and some severe-hail risk may accompany any supercell
structures.
The greatest risk for a supercell -- and perhaps a brief tornado --
will extend from parts of southern VA into northern/central/eastern
NC, where buoyancy and low-level SRH will be the greatest (albeit
modest in magnitude). Overall, however, the lack of stronger deep
ascent could restrict severe coverage to some extent. If a more
substantial severe risk were to become apparent, Severe Thunderstorm
Watch issuance could become necessary later this afternoon or
evening for portions of the region.
..Cohen/Guyer.. 05/11/2017
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...AKQ...MHX...RAH...RNK...RLX...GSP...MRX...JKL...
LAT...LON 34847759 36248311 36858462 37438400 37438241 36917883
35987653 35107640 34847759
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