ZCZC SPCSWOD48 ALL
   ACUS48 KWNS 060855
   SPC AC 060855

   Day 4-8 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0355 AM CDT Thu Aug 06 2020

   Valid 091200Z - 141200Z

   ...DISCUSSION...
   ...Day 4/Sun - Mid-MO to Upper MS Valley Vicinity...

   An active northern stream will persist into at least Day 4/Sun. A
   shortwave upper trough is forecast to extend from Saskatchewan into
   eastern MT/WY early Sunday. The trough will develop east/southeast
   across the northern Plains and Upper Midwest through early Monday
   morning. As this occurs, enhanced westerly deep layer flow will
   overspread the region while a surface low deepens over the northern
   Canadian Prairies. The associated surface trough will extend across
   the eastern Dakotas, with a secondary surface low developing near
   the SD/NE border. As the system tracks eastward during the late
   afternoon and evening, a cold front is forecast to surge
   east/southeast across the northern Plains and Upper Midwest,
   extending across northern WI southwestward into southern NE. A very
   moist and strongly unstable environment will exist ahead of these
   features from the eastern Dakotas/NE eastward through much of the
   Mid/Upper MS Valley. While there is some uncertainty with regards to
   the northern and southern extent of severe potential, most guidance
   develops one or more eastward propagating MCSs across the region
   from late Sunday afternoon into early Monday morning. As such, 15%
   probs have been included across a broad area where favorable
   conditions will exist for damaging winds. 

   ...Day 5/Mon - Central Plains to Mid-MS Valley Vicinity...

   Ongoing convection Monday morning, most likely across parts of the
   Great Lakes, introduces uncertainty regarding severe potential from
   WI/MI south and east through the Ohio Valley vicinity. Further west
   however, conditions should less disturbed to start the day, and a
   very moist/unstable airmass will reside ahead of the surface cold
   front from NE/KS into MO/IL and perhaps as far east as IN. Stronger
   west/northwesterly flow will remain confined to the Great Lakes
   however as the upper trough develops eastward near the international
   border. Strong heating along the surface boundary and weaker
   perturbation migrating through west/northwesterly flow should be
   sufficient for thunderstorm development by peak heating. While one
   or more eastward propagating storm clusters/MCSs is possible in the
   vicinity of the cold front, uncertainty in where convection may
   develop and how widespread it will be, and impacts of prior days
   convection, will preclude severe probabilities at this time. 

   Beyond Day 5/Mon, thunderstorm activity will continue across the
   eastern U.S. but severe potential appears low at this time. Toward
   the end of the period, guidance suggests another shortwave trough
   may develop eastward across the northern Rockies toward the northern
   Plains, and severe potential may once again increase. However,
   confidence is low at this time, precluding severe probabilities.

   ..Leitman.. 08/06/2020

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