SPC AC 210717

   Day 3 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0217 AM CDT Thu Oct 21 2021

   Valid 231200Z - 241200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER A PORTION
   OF THE CENTRAL PLAINS...

   ...SUMMARY...
   Storms may pose a risk for mainly isolated large hail Saturday
   evening/night, primarily across a portion of the central Plains.

   ...Central Plains region...

   Models are trending toward better agreement and have demonstrated
   some run-to-run consistency regarding the evolution of a
   southern-stream shortwave trough forecast to amplify as it
   approaches the southern and central High Plains late Saturday night.
   However, some model differences still persist especially regarding
   the amplitude of this feature. Preceding this impulse, a
   strengthening southerly low-level jet east of an evolving lee
   surface low will foster the advection of partially modified Gulf air
   northward through the southern and central Plains. By Saturday
   evening this low will be situated across western KS with a dryline
   southward through western TX. A warm front will extend east from the
   low through central or northern KS and into southwest MO.
   Destabilization associated with low-level theta-e advection beneath
   plume of steeper mid-level lapse rates will result in moderate
   instability across KS overnight. Increasing isentropic ascent north
   of the warm front promoted by the low-level jet should contribute to
   development of elevated storms across northern KS and adjacent areas
   of southeast NE, northwest MO and southwest IA. Steep mid-level
   lapse rates, moderate instability and sufficient effective bulk
   shear for mid-level updraft rotation will contribute to a threat for
   large hail overnight, especially before storms consolidate into an
   MCS.

   A conditional, somewhat greater severe threat exists for the
   possibility of surface-based storm initiation along the warm front
   across central/northern KS. At this time the probability of this
   scenario appears low, but will be re-evaluated in day 2 updates.

   ...Southern Plains...

   A conditional risk for a couple of strong to severe storms will
   exist from western OK into northwest TX Saturday during the late
   afternoon and early evening. However, relatively weak convergence
   along the dryline and limited deeper forcing, along with the
   likelihood of a capping inversion suggest it should be difficult to
   initiate surface-based storms.

   ..Dial.. 10/21/2021

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