SPC AC 251245

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0745 AM CDT Fri Aug 25 2023

   Valid 251300Z - 261200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   THE MIDWEST...

   ...SUMMARY...
   Isolated to scattered thunderstorms associated with strong wind
   gusts and hail are possible this afternoon and evening especially
   across parts of the the Midwest, and more broadly from the central
   Plains eastward to the Ohio Valley and Mid-Atlantic States.

   ...Midwest...
   With the prominent upper high centered over the southern Plains, a
   shortwave trough (and related speed max) over northern Minnesota and
   nearby Ontario will continue to modestly amplify and spread
   southeastward over the Great Lakes through tonight. While forcing
   for ascent and stronger winds aloft will exist to the north, some of
   these influences will partially overlap a frontal zone across the
   Midwest and Middle Mississippi Valley/Lower Ohio Valley, with the
   easternmost portion of the front convectively modified and more
   southward progressive across the Appalachians/Mid-Atlantic region.

   The aforementioned disturbance appears to be influencing widely
   scattered thunderstorms across Iowa early today. This forcing for
   ascent may interface with the frontal zone later today, where a very
   unstable air mass will reside particularly across southeast Iowa
   into central Illinois and southern Indiana. Even with some
   capping-related uncertainties, concern exists for the possibility of
   at least isolated intense thunderstorm development this afternoon
   into early evening, with the high degree of instability and ~30 kt
   of effective shear potentially supportive of upscale
   growing/east-southeastward-moving clusters capable of wind damage.

   ...Appalachians/Mid-Atlantic States...
   A southward-moving MCS continues to spread generally southward
   across parts of West Virginia/western Virginia as it has tended to
   weaken through the early morning hours. Some later-day thermodynamic
   uncertainties exist related to this MCS, but zones of differential
   heating/terrain influences and lee trough development should lead to
   additional thunderstorm development this afternoon as the boundary
   layer recovers/destabilizes. Some strong to severe thunderstorms
   capable of wind damage will be possible, even while deep-layer shear
   will remain weak. 

   ...Central Plains...
   A front will sag southward across the region, with low-level
   moisture and buoyancy maximized later today near and north of the
   front including eastern Colorado into western/northern Kansas and
   southern Nebraska. As the airmass diurnally destabilizes, an
   increase in thunderstorms is expected across the region into
   mid/late afternoon, with more prevalent thunderstorms this evening.
   Steep lapse rates, moderate buoyancy, and modest strength deep-layer
   shear will support some severe storms capable of hail and
   severe-caliber wind gusts, mostly late this afternoon and evening
   across parts of eastern Colorado, western/northern Kansas, and
   southern Nebraska.

   ..Guyer/Goss.. 08/25/2023

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