ZCZC SPCSWOMCD ALL
ACUS11 KWNS 211930 
SPC MCD 211930 
WVZ000-PAZ000-OHZ000-212030-

Mesoscale Discussion 0481
NWS Storm Prediction Center Norman OK
0230 PM CDT Mon May 21 2018

Areas affected...Portions of the upper Ohio Valley

Concerning...Severe potential...Watch unlikely 

Valid 211930Z - 212030Z

Probability of Watch Issuance...5 percent

SUMMARY...A threat for isolated damaging winds and perhaps an
instance of marginally severe hail exists late this afternoon across
parts of the upper Ohio Valley. The threat will likely remain too
unorganized for watch issuance, however.

DISCUSSION...After developing within a weak warm-advection regime
over southwest Ohio this morning, thunderstorms have slowly evolved
eastward this afternoon, with some recent southward component of
propagation into stronger instability. One cell over Washington Co,
OH, has exhibited a deepening reflectivity core over the last hour
or so, likely in response to ongoing boundary-layer destabilization.
While flow aloft is not particularly impressive, these cells exist
on the southern fringe of stronger 500mb westerlies, with about 25
kt of effective shear promoting multicellular evolution. As
convection continues east/southeast, a few instances of gusty,
potentially damaging winds may be realized. Relatively poor
mid-level lapse rates will temper hail growth aloft, but an instance
of marginally severe hail could occur as well. Considering the
low-end nature of the threat, watch issuance is not expected.

..Picca/Weiss.. 05/21/2018

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

ATTN...WFO...PBZ...RLX...ILN...

LAT...LON   38988262 39578178 39738048 39718036 39598014 39217992
            38908008 38658040 38118132 38018162 38278221 38628274
            38988262 

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