Mesoscale Discussion 1111
   NWS Storm Prediction Center Norman OK
   0400 PM CDT Sun Jul 05 2020

   Areas affected...Northeast Wyoming/southeast Montana and western
   South Dakota

   Concerning...Severe potential...Watch possible 

   Valid 052100Z - 052300Z

   Probability of Watch Issuance...60 percent

   SUMMARY...The potential for large hail and severe-caliber wind gusts
   is expected to increase through late afternoon/early evening across
   northeast Wyoming and western South Dakota as well as southeast
   Montana. A Watch will probably be needed (by around 4-5pm MDT) for
   at least parts of the region, most likely across northeast
   Wyoming/western South Dakota.

   DISCUSSION...The region is generally influenced by a
   semi-moist/increasingly unstable post-frontal air mass. While some
   diurnal mixing has occurred, near 60F surface dewpoints have been
   maintained near/north of the Black Hills, with middle/upper 50s F
   surface dewpoints extending westward into northeast Wyoming.

   Towering Cu/incipient storm development is noted as of 230pm MDT in
   vicinity of the Black Hills, with other high-based convection
   expected to gradually deepen/mature across interior Wyoming and the
   southern Montana mountains through late afternoon. Such development
   will likely be aided by a subtle mid-level impulse/speed max noted
   in water vapor imagery near the Idaho/Montana/Wyoming border region
   at mid-afternoon.

   With deep-layer winds expected to modestly strengthen into this
   evening, steep lapse rates/moderate buoyancy in the presence of
   40-50 kt effective shear will be conducive for at least isolated
   supercells capable of large hail by late afternoon/early evening.
   This will particularly be the case as storms develop across western
   South Dakota and/or move east-northeastward and reach the somewhat
   richer moisture/greater instability across northeast Wyoming/far
   southeast Montana. This may include the potential for isolated very
   large hail, mainly across northeast Wyoming toward the Black Hills
   vicinity. Aside from a risk for isolated supercells, one or more
   semi-organized storm clusters could organize and move into/across
   western Dakota later this evening with a severe hail/wind risk
   likely continuing.

   ..Guyer.. 07/05/2020

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

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

   LAT...LON   45490908 45660684 44910377 44400259 43660245 43170359
               42960583 44100641 44990762 45490908