SPC AC 150728

   Day 3 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0228 AM CDT Mon Apr 15 2019

   Valid 171200Z - 181200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM PARTS OF
   EASTERN OKLAHOMA AND WESTERN ARKANSAS SOUTHWEST ACROSS PARTS OF
   CENTRAL AND EASTERN TEXAS...

   ...SUMMARY...
   Strong/severe storms are forecast Wednesday afternoon and evening,
   from the Iowa vicinity south-southwest into the southern Plains.

   ...Synopsis...
   A gradually strengthening upper trough will move out of the Rockies
   and into the Plains Wednesday, and will be the primary feature of
   interest this period.  Flanking the trough, ridging will encompass
   the western and eastern portions of the country.

   At the surface, a weak low initially over Kansas is forecast to
   shift northeastward to Iowa by sunset, and then into the northern
   Illinois/Wisconsin area overnight.  Along a trailing cold front,
   models forecast weak secondary/frontal low development over the
   southwest Oklahoma vicinity during the afternoon -- likely near the
   intersection of the front an a southward-extending dryline.  This
   cold front and dryline should focus late afternoon development of
   strong/locally severe storms.

   ...Portions of the central and southern Plains east to the lower
   Missouri/mid Mississippi Valleys...
   As low-level moisture spreads gradually northward on southerly flow
   ahead of the advancing storm system, steep lapse rates associated
   with eastward advection of an elevated mixed layer will result in
   development of a moderately unstable but capped warm sector.  

   Capping should hinder convective development -- particularly over
   the southern Plains -- until late afternoon, but expect storms to
   eventually develop along the cold front, and southward along an
   eastward-mixing dryline as ascent increases in advance of the
   strengthening upper system.

   With flow aloft forecast to gradually strengthen as the trough
   advances, shear sufficient for supercells will reside across much of
   the area by afternoon.  As such, developing storms will likely
   become quickly severe given the degree of CAPE expected, with very
   large hail likely to be the primary severe risk.  Greatest risk for
   the largest hail appears to exist across the southern Plains, near
   the axis of steepest lapse rates associated with the elevated mixed
   layer advecting northeastward from northern Mexico/New Mexico. 
   Damaging wind gusts will also be possible locally, and a tornado or
   two cannot be ruled out.  Convection will continue overnight --
   spreading eastward toward the Mississippi River, but severe risk
   should gradually diminish overnight.

   ..Goss.. 04/15/2019

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