SPC AC 230553

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1253 AM CDT Fri Apr 23 2021

   Valid 241200Z - 251200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS MUCH OF THE
   SOUTHEAST...

   ...SUMMARY...
   Isolated to scattered severe thunderstorms may occur Saturday across
   parts of the Southeast. All severe hazards appear possible,
   including large hail, damaging winds, and a few tornadoes.

   ...Synopsis...
   A broad, low-amplitude, southern-stream shortwave trough is forecast
   to be over the Lower MS Valley early Saturday before then continuing
   quickly eastward across the Southeast states throughout day. Strong
   mid-level flow will accompanying this system, spreading
   eastward/northeastward from the Lower MS Valley across the Southeast
   and into the Mid-Atlantic States.

   Surface pattern will be complicated by widespread thunderstorms over
   the Southeast early in the period (discussed in more detail below),
   but the general expectation is for a convectively enhanced low to be
   centered over northern AL Saturday morning. A warm front will extend
   eastward from this low through central GA and southern SC. This warm
   front is forecast to move northward throughout the day as the
   attendant surface low tracks northeastward.

   ...Southeast into the Mid-Atlantic...
   A large convective complex resulting from thunderstorms over the
   southern Plains and Lower MS Valley Friday night will likely be
   ongoing across the Southeast early Saturday morning, supported
   throughout Friday night and Saturday morning by strong warm-air
   advection. Expectation is for this complex to outrun the low-level
   moisture return, limiting the potential for surface-based storms
   throughout much of the day. The only exception is across
   southern/southeast GA where the southwestern extent of the
   convective cluster could begin to interact with more low-level
   moisture (and resulting buoyancy) during the afternoon. Vertical
   shear over this area will be strong enough to support organized
   storms and the potential exists for a few supercells.

   The shortwave trough will lag behind this storm cluster as will its
   attendant cold front. Elevated character of the cluster suggests any
   cold pool would be unlikely to scour out the low-level moisture, and
   consensus among the guidance is that mid to upper 60s dewpoints will
   be in place across much of MS and AL ahead of the shortwave and cold
   front. As a result, afternoon/early evening thunderstorm development
   appears likely as the air mass destabilizes under diurnal heating
   and ascent increases. 

   Cooler mid-level temperatures closer to the shortwave trough will
   foster steep mid-level lapse rates while accompanying moderate to
   strong mid-level flow supports robust vertical shear. Resulting
   environment appears favorable for supercells with potential to
   produce very large (i.e. greater than 2" hail) as well as damaging
   downbursts. Low-level winds will likely veer ahead of the front, but
   enough low-level vertical shear will exist to support a modest
   tornado threat.

   Given all the factors involved in the severe potential (including
   numerous surface boundaries and uncertain convective evolution),
   delineating an area of higher severe potential is difficult as this
   forecast range. However, one may be needed in subsequent outlooks
   once mesoscale details become better defined.

   ..Mosier.. 04/23/2021

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