Storm Prediction Center Mesoscale Discussion 1579

   Mesoscale Discussion 1579
   NWS Storm Prediction Center Norman OK
   0158 PM CDT Thu Jul 11 2024

   Areas affected...southeastern Arizona and adjacent southwestern New
   Mexico

   Concerning...Severe potential...Watch possible 

   Valid 111858Z - 112200Z

   Probability of Watch Issuance...40 percent

   SUMMARY...Thunderstorms developing across the higher terrain may
   generate strengthening outflow spreading southwestward across lower
   elevations, toward the central/southeastern Arizona international
   border area, through 2-4 PM MST.  This probably will be accompanied
   by strong to occasionally severe wind gusts and blowing dust.  While
   it is not clear that this will require a severe weather watch,
   trends are being monitored.

   DISCUSSION...While morning soundings indicated some increase in
   precipitable water across the region over the past 24 hours or so,
   low-level moisture remains seasonably modest with surface dew points
   across much of the lower deserts forecast to fall into the mid 40s
   to near 50 F by peak afternoon heating and boundary-layer mixing. 
   Still, across the higher terrain, including the Mogollon Rim
   vicinity  of eastern central Arizona into southwestern New Mexico,
   the moisture has been sufficient to support deepening convective
   development and the initiation of thunderstorm activity.

   Beneath a belt of northeasterly to easterly mid-level (cloud-bearing
   layer) flow (initially convectively augmented, but now weakening to
   around 20-25 kt or so), guidance suggests that additional
   thunderstorm development is increasingly probable during the next
   few hours across the higher terrain of southeastern Arizona into
   Sonora.  However, upslope into/across the Mogollon Rim vicinity may
   support the most prominent clustering and upscale growth of
   convection.  

   Gradually, aided by increasing precipitation loading and sub-cloud
   evaporative cooling, strengthening downdrafts appear likely to
   consolidate into larger-scale scale southward and southwestward
   propagating outflow, which may be accompanied by increasing
   potential for strong surface gusts.  Given the weak CAPE evident in
   forecast soundings for the strongly heated and increasingly
   deeply-mixed boundary layer in lower elevations, the extent of
   renewed convective development along/above the outflow remains
   unclear.  However, it appears possible that this could be sufficient
   to support strong to locally severe gusts into the lower deserts and
   across the international border by early evening.

   ..Kerr/Guyer.. 07/11/2024

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

   ATTN...WFO...EPZ...TWC...PSR...

   LAT...LON   33511079 33371017 33150957 33060894 32980839 32400803
               31300905 30971066 31581194 32091125 33251122 33511079