Mesoscale Discussion 698

Issued

May 11, 2017, 4:47 PM EDT (20:47 UTC)

Expired

May 11, 2017, 7:15 PM EDT

In force

2 hr

Issued by

the Storm Prediction Center

Chance of a watch

40%

The Roanoke radar (KFCX), 95 km from the middle of the area, began a volume at 20:50 UTC, the scan nearest the moment this went out.

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• Severe Thunderstorm Watch 211May 11, 7:45 PM EDT

634 
ACUS11 KWNS 112047
SWOMCD
SPC MCD 112047 
NCZ000-VAZ000-WVZ000-TNZ000-KYZ000-112315-

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

Mesoscale Discussions in North Carolina, 2017Mesoscale Discussions in Virginia, 2017Mesoscale Discussions in Kentucky, 2017Every mesoscale discussion in 2017

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.