Mesoscale Discussion 1199
   NWS Storm Prediction Center Norman OK
   1149 AM CDT Sun Jul 12 2020

   Areas affected...Parts of north central Nebraska into south central
   South Dakota

   Concerning...Severe potential...Watch unlikely 

   Valid 121649Z - 121845Z

   Probability of Watch Issuance...20 percent

   SUMMARY...One or two supercells with the potential to produce severe
   hail and wind appear increasingly possible through Noon-2 PM CDT. 
   Isolated storm coverage may limit the need for a severe weather
   watch, but trends will be monitored.

   DISCUSSION...Lift associated with lower/mid tropospheric warm
   advection has likely contributed to ongoing increasing thunderstorm
   development southeast of the Badlands of South Dakota into the
   Sandhills of Nebraska.  It appears that this is being aided by a
   subtle short wave impulse migrating around the periphery of the
   still prominent subtropical ridging centered over the Southwest.

   Model output seems to confirm that initial activity is rooted above
   the boundary-layer, but inflow air may be characterized by CAPE on
   the order of 1000-2000 J/kg.  Pronounced veering of winds with
   height beneath a belt of 20-40 northwesterly flow at 500 mb is
   probably contributing to strong shear in the convective layer, in
   the presence of otherwise generally weak westerly deep-layer mean
   ambient flow.  However, if activity can root within the boundary
   layer, southeasterly near surface flow would contribute to shear
   even more supportive of supercells.

   This appears increasingly possible as early as the 17-19Z time
   frame, as the mid-level impulse continues east-southeastward across
   and east of the Valentine/Broken Bow NE area, where latest objective
   analysis suggests that at least modest boundary-layer
   destabilization is underway.  If this occurs, substantive further
   storm intensification may result in increasing potential for severe
   hail and wind.

   ..Kerr/Guyer.. 07/12/2020

   ...Please see www.spc.noaa.gov for graphic product...

   ATTN...WFO...FSD...GID...LBF...UNR...

   LAT...LON   42430108 43210090 43650005 42619879 41929861 41299916
               41300007 41750080 42430108