SPC AC 191755

   Day 2 Convective Outlook RESENT 1
   NWS Storm Prediction Center Norman OK
   1255 PM CDT Fri Jun 19 2020

   Valid 201200Z - 211200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
   THE NORTHERN PLAINS...

   ...SUMMARY...
   A few strong to severe storms will be possible over portions of the
   Plains into the Midwest region Saturday afternoon and evening. 
   Isolated large hail and locally damaging gusts will be the main
   hazards with these storms.

   ...Northern Plains...

   A shortwave trough embedded within an upper low over the Canadian
   Prairie provinces will eject eastward across the northern Plains
   Saturday afternoon/evening. The region will be behind a surface cold
   front, resulting in modest boundary layer moisture with dewpoints
   generally in the 50s F. However, cold temperatures aloft will result
   in steep lapse rates, aiding in weak destabilization of around
   500-1000 J/kg MLCAPE amid 30-40 kt effective shear. This should
   support storm clusters and a few high-based supercells capable of
   large hail. Steep low level lapse rates and a relatively dry
   sub-cloud layer could also foster locally strong gusts.

   ...Southern High Plains to Mid-MS Valley/Upper Midwest Vicinity...

   Quite a bit of uncertainty remains in the forecast for this region
   on Saturday. A surface cold front will extend from a weak low over
   IA to southeast KS and into OK/northwest TX Saturday morning. Areas
   of showers and thunderstorms will likely be ongoing Saturday
   morning, mainly across the southern Plains. Southwesterly low level
   flow will maintain mid 60s dewpoints ahead of the front, but cloud
   cover will result in modest surface heating from OK northeastward to
   WI. Nevertheless, MLCAPE around 1000-2000 J/kg is expected across
   parts of the mid-MS Valley into northern IL/WI. As the shortwave
   trough over the central Plains shifts eastward during the afternoon,
   thunderstorms are expected to develop from northern MO into IA and
   spread eastward across WI/IL. Increasing 0-6 km shear around 25-35
   kt and a strengthening southwesterly low level jet should support
   organized storm clusters capable of locally strong gusts. In pockets
   of greater instability, modest midlevel lapse rates and marginal
   supercell wind profiles/long hodographs could support isolated hail.

   The severe threat across parts of OK is more uncertain and
   conditional. Some guidance suggests boundary layer recovery will
   occur, such that thunderstorms may redevelop during the afternoon or
   evening along outflows from morning convection. Steep midlevel lapse
   rates and modest shear would support large hail potential.
   Additionally, if strong heating can occur, steep low level lapse
   rates and strengthening southwesterly low level jet could foster
   isolated damaging gusts. 

   Further south into parts of western TX, strong heating is expected
   south of morning outflow/effective frontal boundary, and east of a
   dryline near the NM/TX state line. Diurnally-driven convection is
   expected along the dryline and higher terrain of southwest TX during
   the late afternoon/evening. Steep midlevel lapse rates and modest
   shear will support isolated large hail, while steep low level lapse
   rates aid in strong gusts. Low confidence in storm coverage
   precludes higher probs at this time.

   ..Leitman.. 06/19/2020

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