SPC AC 130556

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1156 PM CST Fri Mar 12 2021

   Valid 131200Z - 141200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM THE TEXAS
   PANHANDLE INTO WESTERN OKLAHOMA...

   ...SUMMARY...
   Scattered severe thunderstorms are expected across the Oklahoma and
   Texas Panhandles, northwest Texas, and western Oklahoma on Saturday,
   with the greatest threat expected from mid afternoon into the early
   evening. A few tornadoes, some possibly strong, and very large hail
   will be the primary hazards, with damaging wind gusts possible as
   well.

   ...Synopsis...

   A cutoff upper low now over the Desert Southwest will drift slowly
   east today and will likely be centered over the southern Rockies by
   12Z Sunday. Weak lee cyclogenesis will occur over the southern High
   Plains in association with this feature. A stationary front situated
   across OK through the TX Panhandle may lift northward to near the KS
   border during the afternoon. Meanwhile, a cold front will advance
   into western TX during the day and likely extend from a the surface
   low over the TX Panhandle southward to the Big Bend area by late
   this afternoon. 

   ...Texas Panhandle through western Oklahoma...

   A few showers and thunderstorms will likely be ongoing north of the
   stalled front from the TX Panhandle through northern OK and into KS.
   The bulk of this activity is expected to shift northward into KS by
   mid day. In wake of any early storms, low clouds may persist in a
   portion of the warm sector, especially from the eastern TX Panhandle
   into OK. This raises some uncertainty regarding how much boundary
   layer destabilization can occur in those regions during the day.
   Farther west from eastern NM into the western TX Panhandle, low
   clouds should mix out just ahead of the front where dewpoints in the
   mid to upper 50s F will reside beneath steep (7.5 - 8 C/km)
   mid-level lapse rates, contributing to 1500-2000 J/kg MLCAPE as the
   surface layer warms. Thunderstorms will likely develop along and
   just ahead of the front across the western TX Panhandle within the
   exit region of a strong mid-upper jet streak. Vertical wind profiles
   will be characterized by very strong effective bulk shear exceeding
   50 kt along with 150-200 m2/s2 0-1 km storm relative helicity. This
   environment will favor discrete supercells as the initial storm mode
   with potential for very large hail and tornadoes, a few of which
   could be strong. The eastern extent of the significant tornado
   threat will depend on how much modification of the surface layer can
   occur where clouds may persist in wake of early storms. If
   sufficient low-level destabilization does occur, then a more
   prolific tornado environment might evolve as storms advance east
   where larger low-level hodographs will exist across the eastern TX
   Panhandle into far western OK. A small moderate risk might be
   warranted for a portion of this area in later updates depending on
   anticipated evolution of the mesoscale environment.  

   ...West Texas...

   Storms will likely develop along the length of the cold front within
   an environment favorable for severe storms including moderate
   instability and strong effective bulk Shear. Initial storm mode
   should be supercellular before activity evolves into a dominant
   linear mode. A couple of tornadoes, large hail and damaging wind
   gusts will be the main threats through mid evening.

   ..Dial/Lyons.. 03/13/2021

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