SPC 1300Z Day 1 Outlook

Day 1 Outlook Image

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0750 AM CDT Tue May 04 2021

Valid 041300Z - 051200Z


Widespread strong to severe thunderstorm development is expected
today across the Deep South. The primary risk will be scattered
severe gusts resulting in wind damage and an accompanying risk for a
few tornadoes.

...East Texas/Deep South/Tennessee Valley...
A moist/potentially unstable air mass exists across a broad region
today, especially from east/southeast Texas to much of
Louisiana/Mississippi/Alabama. As noted in 12Z regional observed
soundings, this is where an elevated mixed layer/plume of steep
mid-level lapse rates of 7.0 C/km (or greater) is established atop
rich boundary layer moisture (surface dewpoints lower 70s) that
precedes an eastward-moving cold front located near the ArkLaTex and
east/southeast Texas early today.
An ongoing MCS across middle/eastern Tennessee will continue to pose
a severe risk early today, mainly in the form of damaging winds and
brief tornado potential, as it continues generally eastward toward
the southern Appalachians.

Elsewhere, near/just north of a front, other strong to severe
thunderstorms are expected to develop this morning across
south-central/east Texas with hail as the primary severe threat
initially. For additional short-term information, see Mesoscale
Discussion 521. 

Influenced by the progressive southern stream shortwave trough,
storms should expand in coverage/intensity into midday/early
afternoon toward the ArkLaMiss vicinity with a corresponding uptick
in wind damage potential expected aside from a persistent severe
hail risk. Strengthening belt of southwesterly low/mid-tropospheric
winds will support organized storms including upscale quasi-linear
growth this afternoon. The net result is a swath of damaging wind
gusts are expected this afternoon especially from central/eastern
Louisiana into central/southern Mississippi and Alabama, and
eventually western Georgia by early evening. While damaging winds
are likely to be the most common hazard, some hail and a couple of
tornadoes will also be possible.

...Ohio Valley and Mid-Atlantic States...
Scenario will be influenced by an early day MCS across the Tennessee
Valley/southern Appalachians and extensive showers/thunderstorms
across the lower/middle Ohio River Valley and related cloud canopy.
For these reasons, considerable uncertainty exists regarding the
degree of diurnal destabilization across the Ohio Valley later this
afternoon, although a few strong/severe thunderstorms may develop
near/ahead of an east/southeastward-moving cold front. The remnants
of the MCS centered across eastern Tennessee early today may persist
eastward across the Appalachians with renewed development this
afternoon into downstream areas of the Mid-Atlantic/Carolinas, with
isolated wind damage as the primary hazard.

..Guyer/Kerr.. 05/04/2021

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