Severe Storm Outlook Narrative (AC)
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000
ACUS11 KWNS 121542
SWOMCD
SPC MCD 121542
PAZ000-WVZ000-OHZ000-KYZ000-INZ000-121815-

Mesoscale Discussion 0036
NWS Storm Prediction Center Norman OK
0942 AM CST Thu Jan 12 2017

Areas affected...Portions of OH...southeastern IN...northern
KY...western PA...western WV

Concerning...Severe potential...Watch unlikely

Valid 121542Z - 121815Z

Probability of Watch Issuance...5 percent

SUMMARY...Showers and thunderstorms crossing the middle Ohio Valley
region and vicinity may produce locally strong wind gusts through
the afternoon hours. A few marginally severe wind gusts cannot be
ruled out, and the addition of a Marginal Risk area is planned
across portions of the area and vicinity for the 1630Z Day-1
Convective Outlook. However, Watch issuance is not anticipated.

DISCUSSION...The 12Z soundings at Wilmington OH and Pittsburgh PA
sampled strong 850-mb southwesterly flow -- on the order of around
60 kt -- accompanying a LLJ overlying the local area. The related
return of marginal boundary-layer moisture -- e.g. surface dewpoints
around the middle 50s -- continues ahead of a sharp cold front
analyzed from northwest OH to southern IL. As the cold front
continues to advance into the modestly moist/marginally unstable air
across the middle OH Valley region and vicinity, and weak
pre-frontal isentropic ascent continues, bands of showers and widely
scattered thunderstorms will spread eastward/northeastward through
the afternoon hours. Convective sustenance has already been noted
across parts of IN. This activity will likely grow in areal coverage
and intensity as weak boundary-layer destabilization occurs eastward
amidst pockets of weak diurnal surface-layer heating. Convective
momentum transport -- augmented by the frontal circulation -- may
support locally strong wind gusts. A few marginally severe wind
gusts cannot be ruled out. Widespread cloud coverage ahead of the
front will limit boundary-layer destabilization, mitigating a more
substantial severe risk.

..Cohen/Kerr.. 01/12/2017

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

ATTN...WFO...PBZ...RLX...CLE...ILN...LMK...IND...

LAT...LON   39518578 40368438 41278121 41028013 40348045 39218201
            38368505 38538613 39518578




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