...POTENTIALLY DANGEROUS SITUATION (PDS) IS SETTING UP FOR THIS AFTERNOON AND EVENING...

 

Mesoscale Discussion 1978
   NWS Storm Prediction Center Norman OK
   1120 AM CST Tue Nov 29 2022

   Areas affected...northern LA...extreme southeast Arkansas and into
   central MS

   Concerning...Severe potential...Tornado Watch likely 

   Valid 291720Z - 291945Z

   Probability of Watch Issuance...95 percent

   SUMMARY...A PDS tornado watch will be needed by 19z/1pm CT for
   portions of northern Louisiana, extreme southeast Arkansas and into
   central Mississippi. Tornadoes, a couple potentially long-track and
   strong, large hail and damaging gusts will be possible into the
   evening hours.

   DISCUSSION...Rich Gulf boundary-layer moisture continues to rapidly
   return northward across the Lower MS Valley vicinity. Surface
   dewpoints near 65 F have developed as far north as south-central MS
   and northern LA late this morning. Meanwhile, the marine warm front,
   roughly delineating 70 F dewpoints, extends west-to east from
   southeast TX through central LA into southern MS. Moisture should
   continue to rapidly increase across northern LA into far southeast
   AR and MS through the afternoon. A plume of steep midlevel lapse
   rates will continue to overspread the region, aiding in MLCAPE
   increasing to 1000-2000 J/kg by mid-afternoon. Breaks in cloud cover
   across northeast LA into central MS will further aid in
   destabilization as greater heating occurs within these cloud breaks.

   Strong vertical shear, with effective shear magnitudes greater than
   45 kt is already in place across the region. Regional VWPs and
   profilers already show enlarged, favorably curved low-level
   hodographs with 0-1 km SRH values greater than 250 m2/s. Large-scale
   ascent will remain modest across the region, resulting in a large
   warm sector supporting discrete supercells. One or more bands of
   supercells will be possible within low-level confluence zones. 

   A particular dangerous situation is expected to develop across
   northeast LA into central MS through this evening as multiple
   supercells track across the area. Tornadoes, a couple strong and
   long-track, will be possible, in addition to large hail (scattered
   2+ inch) and damaging gusts.

   ..Leitman/Hart.. 11/29/2022