SPC AC 281958

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0158 PM CST Sun Feb 28 2021

   Valid 282000Z - 011200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   NORTHEAST TEXAS INTO THE MID-SOUTH AND TENNESSEE VALLEY...

   ...SUMMARY...
   Damaging thunderstorm wind gusts, a few tornadoes, and large hail
   will remain possible through tonight from northeast Texas into the
   Mid-South and Tennessee Valley.

   ...20Z Update...
   Severe probabilities have been reduced behind a southeastward-moving
   cold front across parts of north-central/northeast TX and
   southeastern OK. Convection is still expected to increase in both
   coverage and intensity across AR into western/middle TN and northern
   MS this afternoon and evening, with all severe hazards possible. For
   more meteorological information on the short-term severe threat
   across this region, see Mesoscale Discussion 136. Farther east into
   central/northern AL and eastern TN, probabilities for damaging winds
   and a couple tornadoes have been modestly expanded to account for a
   line of storms along the cold front overnight that may still pose an
   isolated severe risk.

   ..Gleason.. 02/28/2021

   .PREV DISCUSSION... /ISSUED 1015 AM CST Sun Feb 28 2021/

   ...Synopsis...
   A positively-tilted upper-level trough within the Four Corners
   region will continue to sag southeastward today with a closed low
   aloft eventually developing across AZ/NM. A broad swatch of strong
   mid-level flow will exist from the Texas Big Bend into the Ohio
   Valley and lower Great Lakes. At the surface, a cold front extends
   from a central WI surface low southeastward into MO/OK and west TX.
   The front will be the main focus for severe weather this afternoon.

   ...ARKLATEX into the Mid-South...
   Upper 60s to around 70 F dewpoints are situated to the south of the
   southeastward moving cold front. Broken cloud cover, particularly in
   the ARKLATEX region has allowed temperatures to rise to the low 70s
   F. Areas that continue to see broken cloud cover will support
   1500-2000 J/kg of MLCAPE this afternoon. Effective shear values of
   50-70 kts will support organized storm structures. Deep-layer shear
   is generally parallel to the front and will generally favor linear
   storm mode, though supercells ahead of and embedded within the line
   are possible. Large hail will be possible, particularly early in the
   convective cycle. An area of greater hail risk is evident within the
   ARKLATEX given this morning's observed upstream mid-level lapse
   rates. Very large hail will be possible in this region. Damaging
   wind gusts will generally be the primary threat as convection
   evolves and grows upscale along the boundary.

   Low-level hodographs are supportive of a risk for tornadoes. Again,
   the linear storm mode and the weakness in the flow around 700 mb in
   both observed and forecast soundings should limit the overall
   potential. However, a few embedded supercell and mesovortex
   tornadoes within the convective line may occur.

   ...South TX...
   A conditional threat for large hail will exist from the Edwards
   Plateau into parts of South Texas. There is continuing uncertainty
   with whether storms will develop based on the latest guidance.
   However, deep-layer shear will be strong and forecast soundings
   indicate very long hodographs. Should storms develop, they will
   likely be elevated supercells behind the front.

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