Day 1 Severe Weather Outlook

Valid 041200Z – 051200Z


Severe thunderstorms associated with wind damage, hail and a tornado
threat are possible from this afternoon through tonight in the Lower
Mississippi Valley and along the central Gulf Coast.

…Lower Mississippi Valley and Central Gulf Coast…
An upper-level low will move eastward into the southern Plains today
as southwest mid-level flow develops across the Lower Mississippi
Valley. Ahead of the system, a moist airmass will be in place from
southeast Texas extending eastward to the central Gulf Coast. A
quasi-stationary front will exist along this corridor where strong
warm advection will occur during the day. In response, an east to
west band of elevated thunderstorms associated with a marginal
severe threat appears likely to develop across north-central
Louisiana, south-central Mississippi and south-central Alabama. Hail
and isolated strong wind gusts will be possible with this

Further south, from the front southward to the Gulf Coast, low-end
moderate instability will be in place. Low-level convergence along
the front along with strong warm advection should result in some
thunderstorm development along the front this afternoon. Forecast
soundings early this afternoon near the front from New Orleans
eastward to Mobile show MLCAPE near 1200 J/kg, 0-6 km shear of 50 to
55 kt and 700-500 mb lapse rates of 7.0 to 7.5 C/km. This should
support supercell development associated with wind damage and
isolated large hail. Hodographs show strong directional shear in the
lowest 1 km AGL and speed shear in the low to mid levels, resulting
in 0-3 km storm-relative helicities near 300 m2/s2. This will
support a tornado threat with the supercells that develop along or
near the boundary. Cells that move north of the boundary may
transition to more of a large hail and isolated wind-damage threat.

As the upper-level low moves eastward across the southern Plains
this evening, a surface low and associated cold front will move
eastward into the lower Mississippi Valley. Thunderstorms appear
likely to develop near and to the north of the surface low. A line
segment appears likely to organize and move from west to east across
the central Gulf Coast region. Cells that develop on the southern
end of this line could be supercellular with a potential for large
hail, wind damage and a few tornadoes. Wind damage and a tornado
threat could also exist with rotating cells embedded in the line.
The leading edge of the line is expected to reach the western
Florida Panhandle late in the period where an isolated severe threat
will be possible.

..Broyles/Nauslar.. 03/04/2020


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