SPC AC 191234

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0734 AM CDT Tue Oct 19 2021

   Valid 191300Z - 201200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE
   MIDDLE MISSOURI VALLEY...

   ...SUMMARY...
   Strong thunderstorms posing a risk for isolated severe hail are
   possible late tonight (early Wednesday morning) across parts of
   northeastern Nebraska and southeastern South Dakota into
   northwestern Iowa.

   ...Middle Missouri Valley including portions of NE/SD/IA...
   A closed low centered over Utah/western Colorado this morning will
   continue eastward and reach the central High Plains by evening. The
   progression of this system will influence modest surface
   cyclogenesis across Kansas/Nebraska in tandem with the sharpening of
   an eastward-moving cold front that will cross the region tonight
   into Wednesday. Pre-frontal moisture advection into the region will
   be modest overall given limited source region availability, but
   middle 50s F surface dewpoints could develop into the middle
   Missouri Valley late tonight. 

   These forcing for ascent/moisture trends are likely to influence a
   nocturnal maximization of thunderstorms, with initial isolated
   development across northern Nebraska/southern South Dakota becoming
   a bit more numerous (scattered) into the overnight in areas near the
   front and near/north of the surface low, including northeast
   Nebraska/southeast South Dakota and northwest Iowa. Steepening
   mid-level lapse rates atop stable but moistening low-levels could
   support MUCAPE near/above 1000 J/kg. Owing to strong deep-layer
   southwesterly winds, very strong shear through the cloud-bearing
   layer could support some elevated supercells capable of isolated
   severe hail overnight.

   ..Guyer/Leitman.. 10/19/2021

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