re: Severe Weather Thread, TX LA MS AL GA FL (Slight) 3/3-3/4

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Mesoscale Discussion 0154
NWS Storm Prediction Center Norman OK
1050 AM CST Wed Mar 04 2020

Areas affected...Portions of far eastern Texas into central
Louisiana and central Mississippi

Concerning...Severe Thunderstorm Watch 42...43...

Valid 041650Z - 041845Z

The severe weather threat for Severe Thunderstorm Watch 42, 43
continues.

SUMMARY...The threat for a few damaging wind gusts and occasional
large hail will continue for the next few hours. Convective trends
will continue to be monitored for the need of additional watches
past WW 042/043 expiration time at 18Z.

DISCUSSION...A 500 mb cutoff low and subsequent modest upper-level
support will gradually drift eastward across TX this afternoon. In
response, strong 850-700 mb WAA has promoted both deep-layer ascent
and elevated buoyancy (1000+ J/kg MUCAPE per 16Z Mesoanalysis) to
support sustained elevated convection north of a quasi-stationary
surface baroclinic zone. Over the past few hours, a few areas of
organized, marginally severe hail-producing convection have been
noted, including elevated bowing segments in central MS and in the
Houston/Walker County TX vicinity. These storms are rooted along the
850 mb baroclinic zone, and given the approach of the upper-low and
constant feed of low-level moist/unstable air, these segments are
expected to continue for the next few hours. With strong deep-layer
shear also in place, these segments may also remain organized and
intense enough to promote isolated damaging wind gusts as well as
marginally severe hail. In addition, strong low-level shear (200+
m2/s2 effective SRH) coincides with an unstable surface airmass
along the surface baroclinic zone across portions of southern LA
into southern MS, and any storm that root in the boundary layer and
latch unto the boundary may produce a tornado.

Later into the afternoon though, the upper-low and associated
associated mid-level ascent will lag the eastward movement of the
WAA axis, suggesting a gradual west-to-east weakening trend in
convection, as supported by 12Z HREF and the latest 12Z HRRR runs.
As such, convective trends will continue to be monitored for the
need of additional watch issuance later this afternoon.

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Sever turbulence being reported throughout the southeast

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