Mesoscale Discussion 1742
   NWS Storm Prediction Center Norman OK
   0229 AM CDT Thu Aug 15 2019

   Areas affected...Parts of eastern Wyoming...southwestern South
   Dakota and northwestern Nebraska

   Concerning...Severe potential...Watch unlikely 

   Valid 150729Z - 150930Z

   Probability of Watch Issuance...20 percent

   SUMMARY...A relatively isolated, but intense storm probably will
   continue to pose at least a localized severe hail and wind threat
   across northern portions of the Nebraska panhandle through daybreak.
    Barring further upscale growth, it is not certain that a watch is
   needed, but trends will continue to be monitored.

   DISCUSSION...A number of generally low amplitude mid/upper waves
   appear to be progressing through broader-scale anticyclonic
   mid/upper flow across the northern Rockies and Plains.  In
   association with one of these perturbations, forcing for ascent
   appears to be aiding ongoing thunderstorm development now south of
   the Black Hills, near the western Nebraska/South Dakota border area.

   The strongest convection, mainly limited to an isolated but
   sustained supercell, has been confined to areas west/southwest of
   the Black Hills during the past few hours, aided by inflow of
   moderate CAPE of 1500-3000 J/kg, in the presence of steep
   lower/mid-tropospheric lapse rates.  Large-scale forcing for ascent
   associated with warm advection along a tightening mid-level thermal
   gradient (roughly around 700 mb) also appears to be providing
   support for this storm.  This front extends east-southeastward
   across northern portions of the Nebraska panhandle, and may provide
   a continuing focus and support for the maintenance of intense
   convective development into areas northeast of Alliance NE through
   9-11Z.

   Reflectivity associated with the isolated supercell has recently
   transitioned to more of a bowing structure, in the presence of
   strong deep-layer shear, likely accompanied by at least localized
   strong to severe surface gusts.  This threat may continue, along
   with a risk for severe hail through daybreak.

   ..Kerr/Thompson.. 08/15/2019

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

   ATTN...WFO...LBF...UNR...CYS...

   LAT...LON   43660482 43610386 43290276 42800174 42210127 41830188
               42040296 42330354 42730405 43250463 43660482