SPC AC 260550

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1250 AM CDT Fri Apr 26 2024

   Valid 271200Z - 281200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FOR MUCH OF
   OK...PARTS OF NORTH TX...CENTRAL/EASTERN KS...NORTHWEST
   MO...SOUTHEAST NE...SOUTHWEST IA...

   ...SUMMARY...
   Potentially widespread strong to severe thunderstorms are expected
   Saturday into Saturday night. The greatest threat is currently
   anticipated across parts of the central and southern Plains, where
   very large hail, damaging winds, and a few strong tornadoes will be
   possible. A larger area of potential threat will extend from
   south-central Texas north-northeastward into the Great Lakes.

   ...Synopsis...
   A shortwave trough and attendant surface low are forecast to
   gradually weaken and move northeastward across the upper Great Lakes
   region on Saturday. Meanwhile, a deep mid/upper-level trough will
   move eastward from the Southwest, resulting in a deepening cyclone
   across southwest KS. Rich low-level moisture will continue to stream
   northward across the warm sector of this cyclone, and extend
   northeastward along/ahead of the front into parts of the upper
   Midwest and Great Lakes. 

   ...Central/southern Great Plains...
   A complex but potentially significant severe weather episode is
   expected on Saturday, with the greatest threat currently expected
   from parts of central/eastern KS into central/western OK and north
   TX. All severe hazards will be possible, including the threat for
   strong tornadoes and very large hail. 

   Evolution of the warm sector and storm development on Saturday will
   be complicated by the potential for early-day convection spreading
   northeastward from northwest TX through OK into eastern KS. This
   convection would likely initiate late in the D1/Friday period as
   low-level moisture streams westward in conjunction with a retreating
   dryline, beneath steep midlevel lapse rates. While most guidance
   depicts some sort of early convection, its forecast evolution varies
   widely among both CAMs and parameterized convection within mesoscale
   and global models. Some severe threat could accompany this
   convection as it moves northeastward through the day. 

   Strong low-level southerly flow will support recovery in the wake of
   any morning convection. Diurnal storm development will be possible
   in the vicinity of the dryline and also near a northward-moving warm
   front extending east-northeast from the deepening cyclone. 

   For the dryline regime, supercell development will become
   increasingly possible by late afternoon, as MLCINH diminishes and
   some influence of the approaching upper trough begins to overspread
   the region. Moderate to strong buoyancy and strengthening deep-layer
   shear will support an initial threat of very large hail (potentially
   2-3 inches in diameter). The tornado threat will increase into early
   evening, due to a notable increase in the low-level jet (and related
   shear/SRH) with time and eastward extent. Any persistent supercells
   will pose a threat of strong to potentially intense tornadoes as
   they move northeastward. Dryline storm initiation may be somewhat
   greater in coverage from west-central KS into northwest OK, in
   closer proximity to stronger large-scale ascent, though at least
   isolated development will be possible into southwest OK and
   northwest TX. 

   For the warm-front regime, initial development may tend to be
   focused near the dryline/front intersection across north-central KS,
   with more isolated initiation possible northeastward along the front
   as capping is gradually eroded. Moderate to strong buoyancy and
   favorable low-level and deep-layer shear will support supercell
   potential within this regime. All severe hazards will be possible,
   including the potential for very large hail and a strong tornado.
   With time, increasing storm coverage will likely halt the northward
   progression of the warm front, with one or more storm clusters
   moving near/north of the front through the evening with a continued
   severe threat. 

   Aside from the dryline and warm-frontal regimes, diurnal development
   across the broader warm sector will be possible within a moist and
   weakly capped environment, particularly from central OK into eastern
   KS. Evolution and coverage of diurnal warm sector development remain
   uncertain, but the environment will support supercell development
   with a threat of tornadoes and very large hail. 

   Storm coverage will likely increase into the evening, as large-scale
   ascent attendant to the approaching shortwave trough overspreads the
   region. Convection may tend to organized into a QLCS overnight.
   While magnitude of the severe threat with overnight convection
   remains uncertain, favorable moisture and a strong low-level jet may
   continue to support at least some threat for all severe hazards,
   both within the warm sector and eventually along a trailing cold
   front into parts of central/southwest TX.

   ...Northwest KS/southwest NE into northeast CO...
   Low-level easterly flow will maintain modest low-level moisture
   within the post-frontal regime from northwest KS/southwest NE into
   northeast CO. Steep midlevel lapse rates will support MLCAPE
   increasing to near/above 500 J/kg, with veering wind profiles
   supporting potential for organized convection. A supercell or two
   could evolve within this regime, with an attendant threat of large
   hail and possibly a brief tornado.  

   ...Parts of the Upper Midwest/Great Lakes...
   A separate regime of at least isolated severe-thunderstorm potential
   remains evident along/ahead of the cold front from eastern IA into
   parts of the Great Lakes region. While the influence of the ejecting
   shortwave trough initially over the Upper Great Lakes may remain
   mostly displaced from the warm sector, diurnal
   heating/destabilization and decreasing CINH may support isolated
   storm development by late afternoon along the cold front. Deep-layer
   shear will remain sufficient for organized convection, supporting
   conditional potential for supercells and/or stronger clusters
   capable of producing hail, damaging gusts, and possibly a tornado or
   two. 

   Some increase in storm coverage will be possible into the evening as
   the cold front moves southeastward. Eventually, convection should
   generally weaken overnight across this region, though a stronger
   cluster to two could move from eastern portions of the central
   Plains toward the upper MS Valley before the end of the forecast
   period.

   ..Dean.. 04/26/2024

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