SPC AC 270604

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0104 AM CDT Sun Apr 27 2025

   Valid 271200Z - 281200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR MUCH OF THE
   GREAT PLAINS...

   ...SUMMARY...
   Isolated to scattered severe thunderstorms are possible on Sunday
   evening into early morning Monday across parts of the Great Plains.
   Large hail, severe gusts, and a few tornadoes are all possible.

   ...Synopsis...
   A deep mid/upper-level trough will move eastward across the western
   CONUS today. A strong jet will move through the base of the trough
   and begin to impinge on the central/southern Great Plains by
   evening. The primary surface low will deepen through the day over
   the central High Plains and move northeast across NE/SD late
   tonight. A secondary surface low is expected to develop near/west of
   the Black Hills during the afternoon. A lee trough/dryline will
   extend southward into the southern High Plains. Relatively rich
   low-level moisture will initially be confined to the southern Plains
   this morning, but will stream quickly northward later today and
   tonight in advance of the surface lows and dryline. 

   ...Northern Great Plains...
   Large-scale ascent is expected to increase by evening across the
   northern Great Plains vicinity, in association with the approaching
   mid/upper-level trough and jet that will overspread the region.
   Richer low-level moisture will remain mostly south of this region
   through much of the day, but steep midlevel lapse rates, moderate
   buoyancy, and increasing deep-layer shear will support development
   of a few supercells by evening with a threat of hail and damaging
   winds. 

   The longevity of any surface-based storms is uncertain and could be
   limited, but some tornado threat could evolve with any supercells
   that can persist into the evening, as low-level moisture and shear
   continue to increase. Some clustering and upscale growth will be
   possible later tonight, with a threat for hail and damaging wind
   potentially spreading eastward across the Dakotas into MN before the
   end of the period. 

   ...Central/southern High Plains...
   Conditionally, the warm-sector environment across the central and
   southern High Plains will become quite favorable for organized
   convection, with strong instability developing by late afternoon in
   conjunction with strengthening low-level and deep-layer shear.
   However, despite diminishing MLCINH from afternoon into early
   evening near the dryline, there is only an inconsistent and
   relatively limited signal for initiation. 

   One area of potential development will be from west-central NE into
   northwest KS, in the vicinity of the primary surface low. Guidance
   also has a somewhat stronger signal for development into parts of
   the southern High Plains, where strong heating/mixing may result in
   more favorable low-level convergence on the dryline. There is a
   relative minimum in signal for storm development from
   west-central/southwest KS toward the OK Panhandle, but any supercell
   that develops within this region would be within an increasingly
   volatile environment during the evening, and pose an all-hazards
   severe threat. 

   Given the very favorable environment and at least some potential for
   isolated supercell development by early evening in the vicinity of
   the dryline, the Slight Risk has been expanded southward for the
   conditional all-hazards threat. It remains possible that portions of
   the Slight Risk may see little or no storm development.

   ..Dean/Halbert.. 04/27/2025

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