Mesoscale Discussion 1158
   NWS Storm Prediction Center Norman OK
   0151 PM CDT Thu Jul 09 2020

   Areas affected...Parts of northeast Wyoming into southwest South
   Dakota and far northwestern Nebraska

   Concerning...Severe potential...Watch possible 

   Valid 091851Z - 092045Z

   Probability of Watch Issuance...40 percent

   SUMMARY...Deep convective development is expected within the next
   few hours. Large hail and damaging winds are expected to be the
   primary threat with the stronger storms. An isolated tornado cannot
   be ruled out.

   DISCUSSION...CU are beginning to develop per latest visible
   satellite imagery across northeast parts of WY into southwest SD in
   the presence of strong diurnal heating and the approach of a small
   mid-level vort max. As convective inhibition continues to erode,
   initiation should transpire within the next couple of hours. 8+ C/km
   mid-level lapse rates atop a well-mixed boundary layer, as shown by
   the latest SPC Mesoanalysis, is contributing to 1500 J/kg MLCAPE
   across the region, that combined with 40 knots of effective bulk
   shear, may support organized, vigorous updrafts. KUDX VWPs show a
   relatively straight hodograph in the lowest few km, indicative of
   splitting supercells as the primary mode of convection. Steep
   low-level lapse rates and a well-mixed boundary layer will support
   damaging winds and large hail as the primary severe threat.

   An outflow boundary from earlier convection farther east has stalled
   along the NE/SD border. While upslope flow will contribute to
   low-level convergence for storm initiation along the higher terrain
   in WY, additional convergence along the outflow boundary suggests
   that storm initiation may eventually occur here as well. RAP
   forecast soundings also depict larger, clockwise hodographs in
   closer proximity to this boundary, and any supercell structure that
   can become sustained and traverse this boundary may acquire
   low-level rotation. As such, a tornado cannot be completely ruled
   out.

   ..Squitieri/Guyer.. 07/09/2020

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

   ATTN...WFO...LBF...UNR...CYS...BYZ...RIW...

   LAT...LON   42460198 42190259 42100335 42250417 42770492 43790596
               44490611 44800578 44790454 44410335 43740253 42960187
               42460198