Mesoscale Discussion 1544
   NWS Storm Prediction Center Norman OK
   1046 PM CDT Fri Aug 21 2020

   Areas affected...Parts of southern Arizona

   Concerning...Severe potential...Watch unlikely 

   Valid 220346Z - 220615Z

   Probability of Watch Issuance...5 percent

   SUMMARY...Strong thunderstorm generated wind gusts may impact
   portions of Santa Cruz and Pima counties by Midnight-2 AM MST.

   DISCUSSION...Deep-layer ambient mean flow beneath upper ridging is
   generally light and variable near the Arizona/Sonora vicinity. 
   However, easterly/southeasterly flow at mid-levels (centered around
   500 mb) appears to be contributing to a west-northwesterly
   propagation of vigorous thunderstorm development off the higher
   terrain of northern Sonora.  This is now generally focused along a
   conglomerate, convectively generated surface cold pool, which may be
   maintained several more hours as inflow of moist air characterized
   by large CAPE (perhaps up to 4000 J/kg) continues.  

   While cooler and more stable boundary-layer air is maintained 
   across much of southeastern Arizona, stronger thunderstorm
   development seems likely to remain focused south of the
   international border, across northern Sonora.  However, a
   northwestward surge of the cold pool and associated vigorous
   thunderstorm development is possible late this evening, toward
   portions of south central Arizona, where the remnants of a hot,
   moist and deeply-mixed daytime boundary layer, may contribute to the
   potential for strong surface gusts.

   ..Kerr/Edwards.. 08/22/2020

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

   ATTN...WFO...TWC...

   LAT...LON   31401079 31230948 30961006 30411032 30181104 31491229
               31901165 31401079