SPC AC 231639

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1139 AM CDT Sat Sep 23 2023

   Valid 231630Z - 241200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
   OF EASTERN KANSAS...WESTERN MISSOURI...EASTERN OKLAHOMA AND FAR
   NORTHWEST ARKANSAS...

   ...SUMMARY...
   Large to very large hail, wind damage and a few tornadoes will be
   possible today across parts of the Upper Midwest, Lower Missouri
   Valley to the southern Plains. A tornado or two may also occur in
   parts of the coastal Mid-Atlantic.

   ...Upper Midwest/Lower Missouri Valley/Southern Plains...
   A cluster of storms with history of periodic large
   hail/severe-caliber wind gusts this morning across eastern Nebraska
   persists into western Iowa at midday, while generally trending
   downscale and a bit weaker. These storms seem likely to outpace the
   primary reservoir of buoyancy with greater early-day inhibition with
   eastward extent, but some short-term severe risk may nonetheless
   continue.

   This convection casts some uncertainty regarding the northward
   extent of more appreciable surface-based destabilization later
   today, but strong/potentially severe thunderstorm redevelopment is
   still expected later this afternoon near the surface wind
   shift/occluded front. This would primarily be the case beginning
   around mid/late afternoon, coincident with the approach of the upper
   vort/speed max over South Dakota/northern Nebraska/northwest Iowa
   vicinity. At least a modest corridor of severe-conducive instability
   may materialize especially across northwest Missouri/west-central
   Iowa and southwest/south-central Minnesota. Supercell-favorable
   hodographs will reside across much of the region, with the potential
   for large hail, damaging winds, and possibly tornadoes, particularly
   if more cloud breaks/destabilization occurs in proximity to the
   surface low/triple point.

   Farther south, another corridor of persistent convection since
   mid-morning has been across far eastern Kansas into
   northwest/western Missouri. These storms have occasionally produced
   severe hail, and this may continue for a time this afternoon even as
   warm advection/850 mb convergence weakens.

   The primary scenario is otherwise expected to near-frontal deep
   convective development late this afternoon into evening, with a
   moderate to strongly unstable environment, particularly to the
   southwest of the eastern Kansas/northwest Missouri early day storms.
   Steep lapse rates/ample buoyancy and enlarged hodographs will
   support initial supercell potential, capable of very large/damaging
   hail, severe wind gusts and possibly some tornado risk, with storms
   tending to grow upscale during the evening.

   CAPE will lessen somewhat with southwestward extent into
   north-central/northwest Texas where greater boundary-layer mixing
   and lesser dewpoints will be found, but with greater DCAPE and
   downdraft-acceleration potential in support of local wind threat.

   ...Mid-Atlantic States/Tidewater...
   Currently centered over northeast North Carolina, Tropical Storm
   Ophelia is expected to continue to weaken as it generally moves
   north-northeastward through tonight. Reference the National
   Hurricane Center for latest details. Even while the system will
   gradually weaken, some tornado risk will focus along coastal areas
   of southeast Virginia toward the Delmarva today, and possibly
   eventually as far north as New Jersey. Any such potential is
   expected to generally relate to convection that can deepen/sustain
   and pivot toward the coast, especially if it interacts with the warm
   front where low-level/deep-layer shear will be maximized with
   surface-rooted buoyancy.

   ..Guyer/Dean.. 09/23/2023

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