SPC AC 200730

   Day 3 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0230 AM CDT Mon Jul 20 2020

   Valid 221200Z - 231200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   THE NORTHEAST INTO THE MID-ATLANTIC AND OHIO VALLEY...

   ...SUMMARY...
   Isolated strong to severe thunderstorms appear possible Wednesday
   across parts of the Northeast, Mid-Atlantic, and Ohio Valley.

   ...Northeast/Mid-Atlantic into the Ohio Valley...
   A shortwave trough with embedded 30-40 kt mid-level flow should
   overspread eastern parts of the OH Valley into the Northeast and
   Mid-Atlantic on Wednesday. A weak surface low should develop slowly
   eastward across the Great Lakes, with a warm front lifting northward
   across the Mid-Atlantic and Northeast. Low-level moisture is
   forecast to spread northward through the day, especially east of the
   Appalachians. A moderately to strongly unstable airmass should be
   present across the warm sector by peak afternoon heating. The
   forecast combination of instability and shear will likely support
   organized storms, potentially capable of all severe hazards. There
   remains too much uncertainty in guidance regarding the placement of
   greatest instability to include any more than 5% severe
   probabilities for now. But, higher probabilities may be needed once
   models come into better agreement with potential warm sector
   destabilization.

   ...Plains/Midwest...
   Some guidance suggests that a small cluster may be ongoing near the
   NE/KS border at the start of the period. An isolated severe threat
   could materialize if this activity maintains itself as it spreads
   eastward across the Midwest. Regardless, confidence is too low in
   this scenario occurring to include any severe probabilities at this
   time. Otherwise, mid-level heights are forecast to rise over much of
   the Plains through the period, with overall convective potential
   highly questionable/uncertain.

   ..Gleason.. 07/20/2020

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   NOTE: THE NEXT DAY 3 OUTLOOK IS SCHEDULED BY 0730Z