Mesoscale Discussion 1322
   NWS Storm Prediction Center Norman OK
   0259 PM CDT Thu Jul 23 2020

   Areas affected...Eastern Montana and the western Dakotas

   Concerning...Severe potential...Watch possible 

   Valid 231959Z - 232200Z

   Probability of Watch Issuance...60 percent

   SUMMARY...Thunderstorms developing in the coming hours will pose a
   severe hail and wind risk. Trends will be monitored, and a watch is
   possible.

   DISCUSSION...Recent GOES visible imagery shows a well pronounced
   surface low over southeast MT, slowly moving to the northeast. A
   trough axis/dryline is noted in surface observations draped to the
   east/southeast into western SD. Increasingly agitated cumulus has
   been noted along this trough/dryline and in the vicinity of the
   surface low, suggesting that boundary-layer mixing/deepening is
   ongoing and inhibition is becoming weaker over this region. Daytime
   heating has also contributed to 1000-2000 J/kg MLCAPE in the
   vicinity of these features, and 30-40 knot flow aloft is supporting
   marginal, but sufficient, 25-30 knots of effective bulk wind shear. 


   Convective initiation appears probable in the coming hours, roughly
   in the 22-00Z range per recent hi-res guidance. Boundary-normal deep
   layer shear should support initially discrete cells, though
   confidence in the longevity of discrete storms is somewhat low due
   to weak deep layer shear with increasing northeastward extent.
   Storms will pose the potential for severe hail and wind, especially
   across the MT/SD/ND tri-state region where clearing skies has
   allowed for deeper boundary layer mixing and steeper low-level lapse
   rates. 10-15 knot southeasterly winds along the trough axis and into
   western ND are supporting 50-100 m2/s2 ESRH, suggesting that a
   low-end, but non-zero, tornado threat may exist with any organize
   discrete storm. Trends will be monitored and a watch may be needed.

   ..Moore/Hart.. 07/23/2020

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

   ATTN...WFO...BIS...UNR...BYZ...GGW...

   LAT...LON   44420390 44950425 45420469 46140488 46590562 47300558
               47950522 48480437 48210347 47090254 45910219 45120205
               44570234 44240317 44420390