SPC AC 231247

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0747 AM CDT Sat Oct 23 2021

   Valid 231300Z - 241200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE CENTRAL
   PLAINS AND LOWER MISSOURI VALLEY...

   ...SUMMARY...
   Large hail is expected with thunderstorms late tonight across
   portions of the central Plains and Lower Missouri Valley region.

   ...Central Plains/Lower Missouri Valley/Ozarks...
   Amplification of an increasingly prominent shortwave trough is
   anticipated from the Great Basin toward the central High Plains by
   late tonight. Downstream shortwave ridging will tend to prevail
   across the central/southern Plains and Missouri Valley/Ozarks much
   of the day, where a relatively moist air mass will otherwise
   accompany a northward-shifting warm front.

   Initially, some strong storms capable of hail will persist early
   today across southeast Kansas and far northeast Oklahoma into the
   Ozarks. The stronger updrafts will tend to remain on the
   west/southwest flank of the convection in closer proximity to the
   source region instability. These storms will continue to shift
   eastward and likely further weaken as the low-level jet diurnally
   subsides. 

   The primary severe risk across the region, in the form of large
   hail, is expected to develop after sunset, and particularly through
   the 03Z-06Z/10pm-1am CDT time frame, mainly across
   east-central/northeast Kansas into northern Missouri. This will be
   as initial height falls begin to influence the region via the High
   Plains-approaching upper trough. Scenario will be meaningfully
   influenced by a nocturnally strengthening low-level jet and related
   warm advection/elevated moisture transport, with thunderstorms
   expected to steadily increase across the region, especially in the
   aforementioned spatiotemporal corridor.

   Forecast soundings suggest ample elevated MUCAPE of 2000-3000 J/kg
   will exist via steep mid-level lapse coincident with steady
   moistening just above the stable boundary layer. Strong shear
   through the cloud-bearing layer will support some elevated
   supercells, particularly within the first few hours of increasing
   thunderstorm development this evening and early overnight. A cluster
   of strong/locally severe thunderstorms is expected to persist across
   northern Missouri toward central/southern Illinois through the early
   morning hours of Sunday.

   ...Western Oklahoma and west/northwest Texas...
   Sufficient heating and mixing this afternoon near the surface
   trough/dryline may allow for thunderstorm development across western
   Oklahoma and/or parts of the Texas South Plains/Low Rolling Plains,
   although the residual influence of weak subsidence/mid-level capping
   is expected to keep any such development very isolated. Modestly
   stronger westerlies with northward extent across the region,
   primarily across western Oklahoma and nearby eastern Texas
   Panhandle/Low Rolling Plains, could support a localized severe storm
   risk late this afternoon/early evening. Any storms that do develop
   should diminish into mid/late evening.

   ..Guyer/Kerr.. 10/23/2021

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