SPC AC 230726

   Day 3 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0226 AM CDT Wed Sep 23 2020

   Valid 251200Z - 261200Z

   ...NO SEVERE THUNDERSTORM AREAS FORECAST...

   ...SUMMARY...
   The potential for organized severe thunderstorms on Friday across
   parts of the Upper Midwest appears too uncertain to include any risk
   areas at this time.

   ...Upper Midwest...
   A strong westerly mid/upper-level jet is forecast to persist on
   Friday across much of the Pacific Northwest to the northern Rockies
   and north-central states. A shortwave trough embedded within this
   flow regime should move eastward across the Upper Midwest through
   the period. At the surface, a cold front will likewise sweep
   eastward across this region, with a modest increase in low-level
   moisture occurring ahead of the front across parts of eastern MN
   into western WI and vicinity. At this point, most guidance suggests
   that warm mid-level temperatures preceding the shortwave trough will
   keep the warm sector capped through the day. Still, there is a
   non-zero chance that near-surface-based storms could form along or
   just ahead of the front across parts of east-central MN into
   northwestern WI by Friday evening. If this occurs, then severe
   thunderstorms appear possible given the forecast combination of weak
   instability with strong deep-layer shear. However, the more probable
   scenario is for mainly elevated storms to form north of the warm
   sector Friday evening/night in a low-level warm advection regime,
   with a minimal severe risk farther south. Given these uncertainties
   and model differences, have opted to defer possible inclusion of low
   severe probabilities across this region to a later outlook.

   ...Southeast...
   Isolated to scattered thunderstorms may occur across a broad portion
   of the Southeast on Friday as a weak, positively tilted shortwave
   trough moves eastward over this region. Although mid-level
   southwesterly flow should be modestly enhanced, the lack of any
   discernible surface low, poor mid-level lapse rates, and weak
   instability all suggest that any organized severe thunderstorm risk
   should remain low.

   ..Gleason.. 09/23/2020

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