SPC AC 180727

   Day 3 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0227 AM CDT Tue Apr 18 2017

   Valid 201200Z - 211200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   THE OHIO VALLEY AND LOWER GREAT LAKES...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   THE SOUTHERN PLAINS...

   ...SUMMARY...
   A few strong/severe storms may be possible across parts of the Ohio
   Valley and lower Great Lakes region Thursday afternoon and evening.
   Overnight, isolated severe storms capable of large hail will be
   possible across parts of the southern Plains.

   ...Synopsis...
   A mid-level shortwave trough will advance from the upper Great Lakes
   region to southeastern Ontario, as upstream ridging builds over the
   lower/mid Missouri Valley. Farther west, a trough will progress from
   the Inter-Mountain West to the southern/central Rockies. Along the
   southern periphery of this trough, an impulse will approach the
   southern Plains Thursday night.

   ...Portions of the Ohio Valley and Lower Great Lakes...
   Related to the trough over the Great Lakes and southern Ontario, a
   surface low and attendant cold front will advance east across the
   region on Thursday. Ahead of this front, modest surface heating and
   surface dew points in the lower 60s will contribute to
   marginal/moderate buoyancy, supportive of a few more stout updrafts.
   While wind profiles will be largely unidirectional, westerly
   850-500mb flow of 40-50 kt will offer the potential for some
   convective organization. In turn, thunderstorms may organize into a
   few small bowing segments, capable of strong wind gusts that could
   result in localized damage.

   ...Portions of the Southern Plains...
   As heights aloft lower late Thursday night, convection is forecast
   to increase in coverage in response to a strengthening low-level
   jet. The most likely area for this convection currently appears to
   be across portions of the Texas Panhandle and western/central
   Oklahoma. Steep mid-level lapse rates will favor vigorous
   acceleration within updrafts rooted above the surface. Organized by
   increasing west/southwesterly convective-layer flow, a few of these
   cells may be capable of large hail Thursday night.

   ..Picca/Smith.. 04/18/2017

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   NOTE: THE NEXT DAY 3 OUTLOOK IS SCHEDULED BY 0730Z