SPC AC 260601

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0101 AM CDT Mon Apr 26 2021

   Valid 271200Z - 281200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS PORTIONS OF WEST
   TX AND THE TX PANHANDLE INTO WESTERN/CENTRAL OK AND SOUTH-CENTRAL
   KS...

   ...SUMMARY...
   Severe thunderstorms are possible Tuesday afternoon through Tuesday
   night from portions of West Texas and the Texas Panhandle into
   western/central Oklahoma and south-central Kansas.

   ...Synopsis...
   A deep upper trough is forecast to extend from the northern Rockies
   to off the southern CA coast early Tuesday morning. Gradual eastward
   progression of this trough is anticipated throughout the day as
   strong mid-level flow throughout the base of this system spreads
   eastward into the southern and central Plains. Modest height falls
   will also spread eastward into the southern Plains, interacting with
   the moist air mass already in place. 

   Surface pattern will likely feature a low centered over
   south-central NE, with a dryline extending southwestward across
   central KS and northwest OK, and into the TX Panhandle. This
   boundary is forecast to sharpen throughout the day, before central
   High Plains surface cyclogenesis causes a westward retreat of the
   dryline during the evening.

   ...Southern Plains...
   Complex convective evolution appears likely across the southern
   Plains as multiple mechanisms for initiation interact. The first
   impetus for initiation is expected to be a weak shortwave trough
   moving across the region midday. This shortwave will likely support
   elevated showers and thunderstorms over the warm sector. These
   storms will likely preceded the stronger flow aloft, but steep lapse
   rates could still result in a few storms strong enough to produce
   hail.

   The next impetus for initiation will be convergence along the
   dryline, which will be augmented by large-scale ascent attendant to
   the approaching upper trough. Guidance varies on the how far
   northwest the 60 dewpoints reach by late afternoon, yielding some
   uncertainty as to where initiation will most likely occur. Current
   expectation places the most probable initiation zone from near CSM
   (in southwest OK) to just north of SJT (in southwest TX). Any storms
   that do form will likely become supercellular, with the potential
   for all severe hazards, including very large hail and tornadoes. 

   Lastly, a strengthening low-level jet will aid in additional storm
   development as the dryline retreats westward during the evening.
   Vertically veering wind profiles and steep mid-level lapse rates
   support the potential for strong updrafts. Nocturnal stabilization
   of the boundary layer suggests the primary severe risk with these
   storms will be large hail.

   ...Central High Plains...
   Upslope flow and low-level convergence near a deepening surface low
   will likely result in thunderstorm development over far northeast CO
   and vicinity Tuesday afternoon. Strong vertical shear may result in
   organized updrafts and the potential for a few supercells.
   Additionally, a cold front stalled across the region could augment
   ascent while also provided a corridor for storm progression. 

   ...Upper Midwest...
   Elevated storms early in the period, driven by warm-air advection
   over the front, could occasionally become strong enough to produce
   isolated hail in the vicinity of SD/IA/MN border intersection.
   Additional thunderstorm development is possible later Tuesday
   evening and overnight across southern MI and central WI as the
   low-level jet increases again.

   ..Mosier.. 04/26/2021

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   NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 1730Z