SPC AC 111300

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0800 AM CDT Sun Oct 11 2020

   Valid 111300Z - 121200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE UPPER
   MIDWEST AND MIDDLE MISSOURI VALLEY...

   ...SUMMARY...
   Severe thunderstorms are possible late this afternoon and evening
   across the Upper Midwest and Middle Missouri Valley. Some tornado
   and/or damaging wind potential will also exist across parts of the
   Carolinas.

   ...Upper Midwest/Middle Missouri Valley...
   Considerable upper-level trough amplification will occur over the
   northern High Plains/Dakotas today, with height falls reaching the
   Upper Mississippi River Valley and Middle Missouri Valley by late
   tonight. As amplification occurs, a considerable strengthening and
   backing of mid/high-level winds (50-80 kt at 500 mb; generally
   south-southwesterly) are expected across the region by tonight. The
   stronger winds aloft will be maximized just behind an
   east/southeastward-moving cold front.

   While moisture is quite limited early today, a steady moistening is
   expected with a northward-transitioning warm front. By late
   afternoon/early evening, a semi-narrow zone of upper 50s/lower 60s F
   surface dewpoints are expected near/just ahead of the
   east/southeast-advancing cold front. Mid-level capping will be
   prevalent much of the afternoon, particularly given the modest
   moisture scenario. Regardless, the increasingly pronounced forcing
   for ascent will be instrumental in the development/maturation of
   convection by late afternoon, and more so, into this evening. Such
   initial development is likely to occur generally near the border of
   the eastern Dakotas/western Minnesota into northwest Iowa, with
   other storm development occurring a bit later southwestward into
   eastern Nebraska/northeast Kansas.

   Forecast soundings suggest ample deep-layer shear for potential
   supercells capable of severe hail with initial development. However,
   the strong degree of forcing and influence of the cold front should
   result in relatively quick storm mergers, with the expected
   evolution of a semi-continuous squall line by mid-evening across
   southern Minnesota/western Iowa into southeast Nebraska/northeast
   Kansas. Accordingly, damaging winds will likely be an increasing
   concern this evening, while some line-embedded tornado risk cannot
   be ruled out. Overall storm vigor will likely diminish overnight as
   the storms encounter an increasingly stable boundary layer with
   eastward extent.

   ...Carolinas...
   The remnants of Delta will continue northeastward toward the
   southern Appalachians today. Early morning water vapor imagery shows
   substantial mid-level drying from Georgia into South
   Carolina/western North Carolina. The overall system will tend to
   weaken, as will low/mid-level winds preceding it. That said, some
   severe risk in the form of a brief tornado or two and/or locally
   damaging winds is still expected given sufficiently favorable
   low-level/deep-layer shear and a moist environment. While a
   particularly organized/sustained severe risk is not currently
   expected, a corridor near the South Carolina/North Carolina border
   in vicinity of the warm front would conditionally be the most
   favorable area for a tornado risk.

   ..Guyer/Goss.. 10/11/2020

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