SPC AC 100538

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1138 PM CST Mon Nov 09 2020

   Valid 101200Z - 111200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
   NORTHEAST MO...EASTERN IA...NORTHERN IL AND SOUTHERN WI...

   ...SUMMARY...
   Thunderstorms capable of producing isolated strong to locally
   damaging winds and perhaps a few tornadoes are possible this
   afternoon and evening across portions of the Middle Mississippi
   Valley vicinity.

   ...Mid-Mississippi Valley Vicinity...

   A potent midlevel shortwave trough will become negatively tilted
   today as it ejects east/northeast from northern/central Plains to
   the upper Great Lakes. At the surface, low pressure will deepen at
   it track northeast from MO into eastern IA by midday. Strong
   southerly flow ahead of the surface low and eastward-advancing cold
   front will transport low 60s dewpoints as far north as southern WI
   and southern lower MI. While heating will be limited by cloudy
   skies, cooling aloft will result in steepening midlevel lapse rates
   and modest instability (generally less than 750 J/kg MLCAPE) is
   expected during the afternoon and early evening. Thunderstorms are
   first expected to develop and intensify during the afternoon across
   northern MO into eastern IA. Deep layer flow will generally be
   parallel to the cold front, supporting a more linear storm-mode with
   line segments/QLCS development expected. 

   Given the deepening surface low, some backing of near-surface winds
   is expected closer to the low from eastern IA into northern IL and
   southern WI. This could increase the potential for mesovortex
   formation within the broader QLCS/bowing segments. Forecast
   soundings indeed show enlarged, curved hodographs with both
   increasing directional and speed shear leading to 0-1 km SRH values
   greater than 250 m2/s2. As a result, a few tornadoes are possible,
   in addition to isolated strong/locally damaging wind gusts. The
   severe threat should decrease with time and eastward extent as the
   boundary layer stabilizes with the loss of daytime heating and
   strong forcing ejects northeast over the upper Great Lakes and
   Ontario.

   ...Florida...

   Strong deep layer easterly flow on the eastern periphery of Tropical
   Storm Eta will maintain a moist airmass over the region. Heating
   through cloud breaks will allow for some destabilization of the
   airmass over the Peninsula, but poor lapse rates and weak effective
   shear will limit storm organization. While a couple of storms could
   produce gusty winds, convection is expected to remain sub-severe.

   ..Leitman.. 11/10/2020

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