SPC AC 250729

   Day 3 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0229 AM CDT Thu Aug 25 2022

   Valid 271200Z - 281200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE UPPER
   MISSISSIPPI VALLEY SATURDAY AFTERNOON AND EVENING...

   ...SUMMARY...
   Isolated severe thunderstorms are possible across the Upper
   Mississippi Valley Saturday afternoon and evening.

   ...Upper MS Valley...
   A shortwave trough is forecast to extend from southern Saskatchewan
   southward through the northern Plains early Saturday morning. This
   shortwave is then expected to progress northeastward, moving through
   southern Manitoba and MN and into far northwestern Ontario. A subtle
   surface low will likely move northeastward just ahead of the
   shortwave, progressing from west-central MN northeastward into far
   northwest Ontario throughout the day. 

   Ample low-level moisture is expected within the airmass over the
   region, with afternoon dewpoints in the mid to upper 60s likely.
   Strong heating is also anticipated, with afternoon temperatures in
   the mid to upper 80s. These warm and moist conditions will occur
   beneath steep mid-level lapse rates, resulting in a moderate to
   strongly unstable airmass. The combination of modest large-scale
   forcing for ascent and low-level convergence along a weak surface
   trough amid the favorable thermodynamic conditions is expected to
   result in afternoon thunderstorm initiation. 

   Warm temperatures at the base of the EML result in some uncertainty
   regarding convective initiation, with the potential for some storms
   to be elevated north of the surface trough as well. These
   uncertainties merit low severe probabilities at this forecast range.
   Even so, any surface-based storms that do mature would likely pose a
   severe risk. All severe hazards are possible, including tornadoes,
   but hail appears to be the primary risk.

   ...Elsewhere...
   Scattered to numerous thunderstorms within the monsoonal moisture
   still in place over the Southwest. Isolated thunderstorms are also
   expected from north CA/southeast OR into the northern Great Basin as
   a compact upper low moves across the region. A few storms are also
   possible across the central Plains as a convectively augmented
   shortwave trough gradually shifts east. In each of these areas,
   limited vertical shear and modest buoyancy should keep the severe
   potential low.

   ..Mosier.. 08/25/2022

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