SPC AC 161232

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0732 AM CDT Tue Mar 16 2021

   Valid 161300Z - 171200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS TONIGHT FROM
   SOUTHERN KS TO CENTRAL AND NORTHEAST TX...

   ...SUMMARY...
   Scattered severe thunderstorms with large hail, damaging winds, and
   a few tornadoes are expected tonight across the Plains from Kansas
   to Texas. Isolated severe storms will also be possible today from
   the lower Mississippi Valley to Georgia.

   ...MS/AL/GA today...
   Overnight convection persists this morning in loose clusters along a
   stalled front across northern AL, and farther south in the warm
   sector across south central AL.  Wind profiles have been marginally
   favorable for embedded supercell structures, with effective bulk
   shear near 40 kt and effective SRH of 100-150 m2/s2.  With some
   boost in buoyancy expected with daytime heating, and some eastward
   expansion of the warm sector into GA, the low-end supercell threat
   is expected to persist through the day along the front and residual
   outflows.  Isolated damaging winds/large hail and a tornado or two
   will all be possible.

   ...KS/OK/TX overnight...
   A compact, deep midlevel low over western AZ will progress eastward
   to NM this evening and the TX Panhandle overnight.  Lee cyclogenesis
   is expected this afternoon/evening near the NM/TX border, and the
   surface cyclone will move to northern OK by the end of the period. 
   In advance of the cyclone, low-level moisture (boundary-layer
   dewpoints in the mid-upper 60s) will surge northward from south TX
   and LA to OK and southern AR this evening into tonight on
   strengthening southerly low-level flow.  This moistening will occur
   beneath a plume of midlevel lapse rates of 8-9 C/km, and MUCAPE will
   increase to 2000 J/kg.

   The boundary layer will be capped through the day, but continued
   destabilization and the approach of strong height falls/ascent from
   the west will likely support thunderstorm development early tonight
   from the eastern TX Panhandle into western OK and southern KS.  The
   storms closer to KS will likely remain elevated north of the warm
   front, though wind profiles will favor elevated supercells capable
   of producing large hail and perhaps some strong/damaging gusts could
   still reach the surface.  Farther south in OK, storms should be
   rooted near the surface, with deep-layer shear and buoyancy
   favorable for supercells with very large hail.  Wind profiles will
   also be sufficient for some tornado threat, though uncertainty
   exists regarding storm mode/coverage with southward extent late in
   the period.

   Thunderstorm development will also be possible late tonight in TX as
   a Pacific cold front overtakes the dryline across the Big Country
   and Edwards Plateau.  The frontal storms will move eastward through
   12z with some threat for damaging winds and large hail.  Closer to
   the Ark-La-Tex, some convection will be possible in a strengthening
   warm advection regime from 06-12z along the surface warm front. 
   Mid-upper 60s boundary-layer dewpoints and only weak convective
   inhibition suggest that storms will be rooted very near the surface,
   with all hazards possible.

   ..Thompson/Gleason.. 03/16/2021

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   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z