SPC AC 240729

   Day 3 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0229 AM CDT Mon Aug 24 2020

   Valid 261200Z - 271200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM PARTS OF THE
   UPPER GREAT LAKES REGION SOUTHEASTWARD TO THE MID ATLANTIC REGION...

   ...SUMMARY...
   Greatest risk for severe storms Wednesday appears to exist over
   portions of the Great Lakes across the central Appalachians.  Some
   risk for severe weather will also exist across the northern
   Intermountain region/northern Plains, over parts of Arizona, and
   also in the vicinity of the central/western Gulf Coast area
   depending upon the track/progression of Laura.

   ...Lower Michigan to the Mid-Atlantic region...
   As the remnant cold front extending from the Upper Great Lakes to
   the Mid Atlantic region lingers, the moist boundary layer south and
   southwest of the front should destabilize diurnally.  With weak
   cyclonic disturbances aloft expected to shift southeastward atop the
   front, within fast belt of northwesterly flow, clusters of
   convection are expected to spread across the risk area.  Given the
   strength of the flow field aloft, risk for locally damaging winds is
   apparent, with southeastward-moving convection into the evening
   hours.

   ...Idaho vicinity east to the upper Mississippi Valley...
   A continued series of vorticity maxima will move through the fast
   belt of weakly anticyclonic flow aloft across the northern tier of
   the CONUS.  Though capping should generally limit storm coverage
   over the northern Plains, and modest instability over the northern
   Intermountain region should limit storm intensity, risk for locally
   damaging winds with a few of the stronger storms over this broad
   region is apparent -- from afternoon into the evening hours.

   ...Louisiana/southern and western Mississippi area...
   Track forecasts from the National Hurricane Center show Laura
   crossing the northern Gulf during the day, and moving into southern
   Louisiana as a substantial hurricane during the evening.  However,
   lingering uncertainty is noted with the forecast progression of this
   storm, and thus associated questions exist with respect to location
   and degree of any associated tornado potential.  At this time,
   5%/MRGL risk will be included across much of Louisiana and into
   southwestern Mississippi, but the areal extent -- and possibly
   degree of risk -- is subject to changes in subsequent outlooks. 

   ...Parts of Arizona...
   As weak cyclonic disturbances aloft continue moving
   west-southwestward across Arizona, afternoon heating/destabilization
   should again contribute to convective development over the high
   terrain.  With a couple of storms/storm clusters expected to move
   into the lower deserts through the evening, locally gusty/damaging
   winds will be possible.

   ..Goss.. 08/24/2020

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