SPC AC 251231

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0731 AM CDT Thu Apr 25 2024

   Valid 251300Z - 261200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS THIS EVENING
   ACROSS WESTERN KS AND TONIGHT ACROSS NORTHWEST TX INTO CENTRAL OK...

   ...SUMMARY...
   Very large hail up to 3 inches in diameter and a strong tornado or
   two will be possible this evening across western Kansas.  Large hail
   up to 2.5 inches in diameter, damaging winds to 70 mph and a few
   tornadoes will be possible tonight from northwest Texas into central
   Oklahoma.

   ...Synopsis...
   A midlevel shortwave trough and associated 70 kt jet will eject
   northeastward toward western KS by late tonight and Friday morning. 
   An associated lee cyclone is expected to deepen this afternoon
   across northeast CO, with a sharpening dryline arcing to its south
   across western KS and the TX/OK Panhandles.  Farther east, a warm
   front will continue to move northward from OK into KS, though
   northward progress of the front will be slowed by elevated
   convection (posing an isolated large hail threat) that will
   reinforce the cool side of the boundary during the day.  A somewhat
   bimodal threat distribution is expected - the warm sector in western
   KS and a second corridor overnight from northwest TX into OK.

   ...Western KS this afternoon/evening...
   An unstable warm sector will be present through this evening, with
   boundary-layer dewpoints in the 60s beneath steep midlevel lapse
   rates.  The base of the elevated mixed layer will be relatively
   warm, suggesting the need for surface temperatures into the 80s on
   the immediate moist side of the dryline.  The better potential for
   storm development this afternoon will be across western KS, where
   dryline parcel residence times will be longer and in closer
   proximity to the left-exit region of the approaching mid-upper jet. 
   The initial dryline storms will likely become supercells capable of
   producing very large hail of 2-3 inches in diameter, and these
   storms could continue northeastward as elevated supercells atop the
   warm front.  The potential for a strong tornado or two will increase
   this evening as the storms encounter richer low-level moisture and
   increasing low-level shear.  However, the window of opportunity will
   not be particularly large given the presence of a rain-reinforced
   front to the northeast and increasing convective inhibition by late
   evening.

   ...Northwest TX into OK overnight...
   A general consensus of most overnight forecast guidance suggests a
   southern corridor of greater hail/wind threat starting early tonight
   just off the Caprock and then spreading northeastward over northwest
   TX into southwest/central OK early Friday morning.  Thunderstorm
   initiation will become more probable by 03-06z in association with
   cooling/moistening at the base of the elevated mixed layer,
   coincident with the beginning of eastward movement of the
   dryline/Pacific cold front along the trailing influence of the
   ejecting midlevel trough.  Storm mode will likely trend to
   clusters/line segments while spreading northeastward. 
   Boundary-layer dewpoints approaching the upper 60s beneath steep
   midlevel lapse rates will contribute to MUCAPE in excess of 2000
   J/kg through the overnight hours, which will favor the potential for
   both large hail (especially with any embedded supercells) and
   damaging winds of 60-70 mph.  A few tornadoes may also occur with
   embedded circulations as low-level shear increases tonight.

   ...TX Panhandle/western OK this afternoon/evening...
   A conditionally favorable environment for supercells with very large
   hail and tornadoes will exist this afternoon/evening across the
   eastern TX Panhandle into western OK.  The primary uncertainty here
   will be lingering convective inhibition and substantial uncertainty
   in storm coverage/location along the dryline.  For these reasons,
   have lowered the overall severe threat, but maintained some
   conditional significant severe potential.

   ..Thompson/Kerr.. 04/25/2024

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