Post by SKYSUMMIT on Nov 29, 2022 11:41:05 GMT -6
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
