SPC AC 231831

   Day 3 Convective Outlook AMEND 1
   NWS Storm Prediction Center Norman OK
   0131 PM CDT Tue Apr 23 2024

   Valid 251200Z - 261200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM THE
   EASTERN TX PANHANDLE AND WESTERN OK INTO SOUTHWEST/SOUTH-CENTRAL
   KS...

   AMENDED TO UPDATE FORECAST

   ...SUMMARY...
   Severe thunderstorms are likely from late Thursday afternoon into
   Thursday night across parts of the central and southern Great
   Plains. Very large hail, severe wind gusts, and strong tornadoes
   will all be possible.

   Guidance continues to suggest strong buoyancy will be in place ahead
   of a negatively tilted shortwave trough ejecting across the southern
   High Plains. General forecast expressed in the previous outlook
   remains valid, but confidence in an area of greater severe-weather
   potential has become more apparent with the most recent guidance.
   Late afternoon development is anticipated across the TX Panhandle,
   with these storms quickly becoming severe and capable of large to
   very large hail up to 3" in diameter. Low-level moisture may be
   later to arrive in west-central/southwest KS, delaying convective
   initiation to a few hours later than farther south. Large to very
   large hail is anticipated with initial development across
   west-central/southwest KS as well.

   In both of these areas, storms are expected to move
   east-northeastward off the dryline, encountering strengthening
   low-level southerly flow and environment that is increasingly
   favorable for tornadoes. Low-level shear will continue to
   strengthening into the early evening, and the overall environment
   supports the potential for strong to intense tornadoes if a discrete
   mode can be maintained.

   --- Previous Discussion issued at 0230 AM CDT Tue Apr 23 2024 ---

   ...Synopsis...
   A shortwave trough initially over the Southwest is forecast to take
   on an increasingly negative tilt as it moves eastward towards the
   central/southern Plains by Thursday night into Friday morning. In
   response, a surface low will consolidate and deepen across the
   central High Plains through the day, before moving northeastward
   toward northwest KS/southwest NE by Friday morning. An initially
   stationary surface boundary will move northward as a warm front
   across the central Plains through the day. Along/south of the warm
   front, relatively rich low-level moisture will stream northward to
   the east of a dryline that will become established from the eastern
   TX Panhandle into western KS and eastern CO. 

   ...Southern/central Great Plains...
   Coverage of the severe-thunderstorm threat remains somewhat
   uncertain, but a couple intense supercells are possible by Thursday
   evening near the dryline from western KS into western OK and the
   TX/OK Panhandles. Another round of overnight convection will
   potentially bring the severe threat eastward into a larger portion
   of the central/southern Plains. 

   The warm sector of the deepening cyclone will likely remain capped
   for much of the day, though elevated convection may persist from
   parts of central/eastern KS into eastern OK, to the north of the
   effective warm front. Increasing moisture beneath steep midlevel
   lapse rates will support MLCAPE in excess of 2000 J/kg along/east of
   the dryline, as deep-layer shear strengthens across the region
   through the day. 

   Ascent attendant to the approaching shortwave trough will begin to
   impinge upon the warm sector by late afternoon, with isolated
   supercell development possible near the surface low across southwest
   KS and southward down the dryline into the TX Panhandle. Very large
   hail (potentially 2-3 inches in diameter) will likely be the primary
   initial hazard. A notable increase in low-level flow/shear near and
   after 00Z will also support a tornado threat with any supercells
   that can persist into the evening across parts of western KS/OK. 

   While any initial dryline storms may weaken by mid/late evening due
   to increasing MLCINH with eastward extent, renewed storm development
   is possible overnight along the Pacific cold front from southwest TX
   into western/central KS/OK as stronger large-scale ascent
   overspreads the region. Steep midlevel lapse rates, moderate
   buoyancy, and strong low-level and deep-layer shear will
   conditionally support a severe threat with overnight convection
   across the warm sector, though storm mode may become complex and
   tend toward a linear evolution with time. Severe wind gusts may
   become an increasing threat with the nocturnal convection, though
   hail and a couple tornadoes will also be possible if semi-discrete
   or embedded supercells can be maintained. 

   ...NE/WY border region into northeast CO...
   Low-level southeasterly flow will support modest moisture return
   into parts of northeast CO, southeast WY, and western NE, to the
   north of the deepening cyclone. Thunderstorm development will be
   possible near and to the cool side of the effective warm front
   during the afternoon. While deep-layer shear will be weaker compared
   to areas farther southeast, steep midlevel lapse rates will support
   an isolated hail threat. A tornado also cannot be ruled out, if
   surface-based storms can be maintained within this regime.

   ..Mosier.. 04/23/2024

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