SPC AC 301244

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0744 AM CDT Sat Sep 30 2023

   Valid 301300Z - 011200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THIS
   AFTERNOON/EVENING FROM NM INTO CO...AND FROM NORTHWEST AZ INTO UT...

   ...SUMMARY...
   Isolated strong-severe gusts may occur this afternoon/evening across
   portions of the New Mexico/Colorado, and from northwest Arizona into
   western and central UT.

   ...NM/CO this afternoon/evening...
   Low-midlevel moisture will continue to increase gradually from NM
   into CO through tonight, to the east of the developing midlevel low
   over NV.  Surface heating in cloud breaks will boost MLCAPE to the
   500-1000 J/kg range across central/eastern NM by later this
   afternoon with minimal convective inhibition, with weaker buoyancy
   to the north into CO.  Scattered thunderstorms are expected to form
   this afternoon and continue through late evening from NM into
   southern/central CO.  Though the stronger mid-upper flow will remain
   farther west, inverted-V profiles will favor a few strong-severe
   outflow gusts with multicell clusters.  

   ...UT/northwest AZ area this afternoon/evening...
   A midlevel trough now over CA will evolve into a closed low over NV
   later today into tonight.  On its eastern periphery, a baroclinic
   zone will spread eastward from central NV this morning to western UT
   this evening.  Ascent along the front will help focus the
   development of a band of convection by this evening from northwest
   AZ into western UT, and the convection will spread northeastward
   into tonight.  Buoyancy will be relatively weak (MUCAPE near 500
   J/kg), but strong midlevel flow and lingering steep low-level lapse
   rates will favor the potential for downward momentum transport and a
   few strong-severe gusts.

   ...MN/WI today...
   Elevated convection is ongoing this morning over northern WI in a
   zone of warm advection on the nose of a 40 kt low-level jet.  The
   convection is expected to weaken through the morning as warm
   advection likewise diminishes.  The potential for diurnal,
   surface-based convection is limited along the slow-moving front
   across MN through this afternoon, given background height rises and
   no appreciable forcing for ascent in an environment with weak
   deep-layer vertical shear.  Overall, the threat for large hail
   appears too low to warrant maintaining any outlook areas.

   ..Thompson/Leitman.. 09/30/2023

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