SPC AC 110729

   Day 3 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0229 AM CDT Wed Apr 11 2018

   Valid 131200Z - 141200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM THE
   SOUTHWEST MISSOURI VICINITY SOUTHWARD INTO NORTHEAST TEXAS AND
   NORTHWEST LOUISIANA...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SURROUNDING THE
   ENHANCED RISK AREA...EXTENDING FROM PARTS OF THE MID-MISSOURI VALLEY
   TO THE WESTERN GULF COAST...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SURROUNDING THE
   ENHANCED AND SLIGHT RISKS...

   ...SUMMARY...
   Strong/severe storms are expected to develop Friday afternoon and
   continue into the overnight hours -- centered over a zone extending
   from Missouri to the Sabine River Valley.

   ...Synopsis...
   An upper low/trough is forecast to shift slowly eastward out of the
   Rockies and into the central and southern Plains Friday, with
   gradually strengthening ridges flanking the trough resulting in
   evolution of high-amplitude flow across the CONUS.

   At the surface, a low initially progged to lie in the southeast NE
   vicinity is expected to shift very slowly east along the IA/MO
   border area.  A trailing cold front will march more quickly eastward
   across the central and southern Plains, and is expected to reach the
   middle and lower Mississippi Valley region by the end of the period.

   ...Portions of Iowa southward to east Texas/Louisiana...
   Northward return of low-level Gulf moisture across the south-central
   U.S. combined with gradual mid-level cooling ahead of the
   approaching upper trough will allow marked diurnal warm-sector
   destabilization.  With around 1000 J/kg mixed-layer CAPE progged to
   evolve immediately ahead of the front from southwest Iowa southward
   to eastern Oklahoma, and up to 2000 J/kg southward into parts of
   east Texas and western Louisiana, vigorous afternoon thunderstorm
   development is expected.

   Initial storm mode will likely be supercellular, with
   veering/rapidly increasing flow with height supporting locally
   intense updrafts.  Large hail and locally damaging winds, and
   possibly a few tornadoes, can be expected near and ahead of the
   front in a north-south zone.  With time, upscale growth of
   convection is expected -- mainly from the Ozarks area southward
   where a more moist/unstable airmass supports widespread convection
   through the evening and overnight.  While storms/severe risk will
   likely wane over northern portions of the outlook area during the
   evening, at least some degree of all-hazard severe risk should
   linger into the overnight hours from Arkansas into east Texas and
   Louisiana.

   ..Goss.. 04/11/2018

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