SPC AC 190539

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1239 AM CDT Fri Jun 19 2020

   Valid 201200Z - 211200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
   OF THE PLAINS INTO THE MIDDLE MISSISSIPPI VALLEY REGION...

   ...SUMMARY...
   A few strong to severe storms will be possible over portions of the
   Plains into the Midwest region on Saturday afternoon and evening.

   ..Central and southern Plains into the Midwest regions...

   An upper trough will move from the Plains through the MS Valley
   region Saturday. A very slow-moving or stationary front should
   extend from the upper Great Lakes southwestward into OK. Areas of
   showers and thunderstorms will likely be ongoing mainly along and
   north of the front. The atmosphere is expected to become moderately
   to strongly unstable in moist warm sector south of this boundary
   with 1500-2000 J/kg MLCAPE, and possibly 2500-3000 J/kg MLCAPE where
   steeper mid-level lapse rates will reside across the southern
   Plains. Storms may redevelop and intensify along the front and
   residual outflow boundaries as the surface layer destabilizes during
   the afternoon. Vertical wind profiles will remain modest with 0-6 km
   shear from 25-35 kt supportive of multicells capable of isolated
   damaging wind and hail. During the evening and overnight, additional
   strong to severe storms might develop in vicinity of the front
   supported by a strengthening southerly low-level jet. Considerable
   uncertainty persists regarding evolution and extent of early
   convection, though greatest confidence in afternoon redevelopment is
   across the middle MS Valley region where weaker instability is
   expected. Farther southwest across the southern Plains, initiation
   is more uncertain and storm coverage will likely be more isolated
   due to stronger capping and possible subsidence in wake of the
   shortwave trough. Given lingering storm-scale and mesoscale
   uncertainties, will maintain MRGL this update.

   Other storms might develop over the mountains of southwest TX and
   possibly a storm or two along the weakly convergent dryline.
   However, much of this region will remain within zone of general
   subsidence in wake of the shortwave trough, suggesting coverage will
   probably be sparse, and any activity that does develop should
   diminish after sunset.

   ...Northern Plains region...

   A shortwave trough embedded within the circulation of an upper low
   centered over southern Canada will move through the northern Plains
   during the day accompanied by a weak cold front. Despite somewhat
   modest low-level moisture with dewpoints in the 50s F, cold
   temperatures aloft with -14 C at 500 mb along with diabatic heating
   of the surface layer will result in MLCAPE up to 500 J/kg. Storms
   will likely redevelop along the front across the central Dakotas and
   into NE during the afternoon. Vertical shear will increase to 35-40
   kt with the approach of the shortwave trough with both multicells
   and possibly a couple of supercells capable of a few instances of
   large hail and locally strong wind gusts into the evening. A SLGT
   risk upgrade might be required in later updates.

   ..Dial.. 06/19/2020

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