Mesoscale Discussion 2001
   NWS Storm Prediction Center Norman OK
   0959 AM CDT Mon Sep 23 2019

   Areas affected...Southwest/South-Central AZ

   Concerning...Severe potential...Watch likely 

   Valid 231459Z - 231700Z

   Probability of Watch Issuance...80 percent

   SUMMARY...Multiple rounds of thunderstorms are expected across
   southwest/south-central AZ today, including supercells. Primary
   threat is large hail but strong wind gusts and an isolated tornado
   are also possible. A watch will likely be needed over the next few
   hours.

   DISCUSSION...12Z Yuma (1Y7) sounding sampled an usually moist air
   mass across the region, with a surface dewpoint of 70 deg F and a PW
   value of 1.86 inches. This area of ample low-level moisture extends
   throughout much of the Lower AZ Desert, with surface dewpoints in
   the 70s southwest of the Mogollon Rim. Warm surface temperatures
   coupled with this ample low-level moisture and relatively cool
   temperatures aloft result in an air mass already characterized by
   little to no convective inhibition and moderate buoyancy (i.e.
   1500-2000 J/kg of MLCAPE). In addition to this buoyancy, the
   shortwave trough digging southward into southern CA has promoted
   increased mid-level flow, resulting in strong deep-layer vertical
   shear across much of the region. Recent mesoanalysis estimated
   effective bulk shear is currently 40-50 kt.

   This thermodynamic environment coupled with ascent from the
   approaching shortwave trough will result in widespread thunderstorms
   across the region. Multiple rounds of storms are anticipated.
   Additionally, the strong vertical shear in place is expected to
   promote severe thunderstorm development, some of which could produce
   very large hail (i.e. greater than 2" in diameter). Strong wind
   gusts and a tornado or two are also possible. Convective trends will
   be monitored closely for likely watch issuance over the next few
   hours.

   ..Mosier/Hart.. 09/23/2019

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

   ATTN...WFO...TWC...FGZ...PSR...VEF...

   LAT...LON   33641483 34291432 34641336 34481126 33201076 31881089
               31641202 32431468 33641483