SPC AC 261615

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1115 AM CDT Sun Sep 26 2021

   Valid 261630Z - 271200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THIS
   AFTERNOON/EVENING ACROSS SOUTHEAST AZ AND SOUTHWEST NM...

   ...SUMMARY...
   Isolated severe hail and/or gusts are possible this afternoon and
   evening across southeast Arizona and southwest New Mexico.

   ...Synopsis...
   A closed midlevel low over the northern Gulf of CA will move slowly
   eastward near the southern AZ border through tonight.  Surface
   heating in cloud breaks across southeast AZ/southwest NM, and ascent
   northeast of the midlevel low will support scattered thunderstorm
   development this afternoon into this evening.  Moderate buoyancy
   (MLCAPE near 1000 J/kg) and effective bulk shear of 25-30 kt will
   support the potential for a few semi-organized storm clusters. 
   Isolated strong outflow gusts will be possible with the stronger
   storms given steepening low-level lapse rates.  Though lapse rates
   aloft will not be particularly steep, the moderate buoyancy and
   vertical shear may support isolated, marginally severe hail.

   Otherwise, isolated lightning flashes will be possible through mid
   afternoon with elevated convection over eastern ME with an ejecting
   shortwave trough.  A few thunderstorms are expected this afternoon
   across southwest FL with a weak backdoor cold front and local sea
   breeze circulations.  Overnight, isolated lightning flashes may
   occur with weak elevated convection in the warm conveyor belt  over
   northwest WA, immediately in advance of a midlevel trough and
   baroclinic zone moving eastward over the southeast Gulf of Alaska.

   ..Thompson/Kerr.. 09/26/2021

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