Mesoscale Discussion 1575
   NWS Storm Prediction Center Norman OK
   0340 PM CDT Sat Aug 21 2021

   Areas affected...portions of the Intermoutnain West

   Concerning...Severe potential...Watch unlikely 

   Valid 212040Z - 212230Z

   CORRECTED FOR TYPO

   Probability of Watch Issuance...20 percent

   SUMMARY...Scattered thunderstorm development ongoing across portions
   of NV, ID, UT and WY will continue through this evening with a risk
   for hail and damaging wind gusts with the strongest storms.

   DISCUSSION...As of 2030 UTC, Regional WV imagery showed a
   well-developed mid-level low across the northwestern US. Forecast to
   move east this afternoon and evening, ascent from the low will
   continue to slowly overspread much of the central Rockies and Great
   Basin where a cold front lies from southwestern Wyoming into
   northeastern Nevada. Radar and satellite trends show weak convection
   has emerged across the area with additional development likely over
   the next several hours. Driven by steep mid-level lapse rates
   beneath the cold pocket aloft, RAP soundings indicate around 500
   J/kg of MLCAPE is present. A mid-level speed max of 40-50 kt around
   the base of the trough will support moderately strong shear profiles
   supportive of organized multicells and perhaps weak supercells.
   While buoyancy will be limited, low-level inverted v profiles will
   support strong downdrafts with the potential for damaging wind
   gusts. Cooling 500 mb temperatures (-12 to -14 C) will also support
   the risk of hail, especially with the stronger cells. 

   Hi-res guidance and observational trends suggest the greatest risk
   for organized severe potential may be associated with storms
   currently developing near the cold front from eastern NV, into
   northern UT and western WY. Here, greater lift and buoyancy in
   proximity to the front may contribute to stronger convection and
   better potential for organization. Convective trends will be
   monitored, but uncertainty on the longevity of any organized severe
   threat suggests a watch is unlikely.

   ..Lyons/Guyer.. 08/21/2021

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

   ATTN...WFO...RIW...TFX...SLC...PIH...BOI...LKN...

   LAT...LON   40091347 39801430 39661559 40111589 41581476 43111341
               43981261 44721193 44961132 44871075 44271011 43181001
               42291030 41801065 41381114 40651231 40431276 40091347