SPC Mar 13, 2025 0730 UTC Day 3 Severe Thunderstorm Outlook

Day 3 Convective Outlook  
NWS Storm Prediction Center Norman OK
0229 AM CDT Thu Mar 13 2025

Valid 151200Z - 161200Z

...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF
SOUTHEAST LOUISIANA INTO SOUTHERN AND CENTRAL MS/AL...

...SUMMARY...
A severe weather outbreak is expected on Saturday from the central
Gulf coast states/Deep South into the Ohio Valley. Significant
tornadoes (focused across the South), swaths of damaging gusts, and
hail are expected.

...Synopsis...

An upper cyclone over the Upper Midwest will lift northeast into
Ontario through Saturday evening. Meanwhile, a large-scale upper
trough over the Plains will eject east toward the MS Valley. Strong
southwesterly mid/upper flow (with a 500 mb jet streak near 100 kt)
will overspread the Lower MS Valley/Mid-South vicinity by 00z, and
continue east/northeast overnight into the Ohio Valley and central
Appalachians. An intense south/southwesterly low level jet greater
than 60 kt is forecast to overspread the central Gulf coast/Deep
South into the TN/OH Valley during the late afternoon and nighttime
hours. Rich Gulf moisture with dewpoints in the mid/upper 60s is
expected to be focused over LA/MS/AL and the FL Panhandle, and
possibly as far north as Middle TN and far western GA. 50s to low
60s F dewpoints will extend north into the Ohio Valley. This should
support a widespread risk for severe storms across much of the
central into the southeastern U.S. Saturday into early Sunday.

...Deep South/TN Valley vicinity...

Forecast guidance has generally trended toward less widespread
precipitation coverage Saturday morning as stronger height falls are
not expected until late morning/early afternoon as the Plains trough
ejects and a surface low begins to develop over the Mid-South.
Persistent strong southerly low-level flow will allow for a
moisture-rich boundary layer that should remain relatively pristine
across southeast LA into southern/central MS/AL before convection
develops by midday. Forecast soundings show cooling aloft will
support steep midlevel lapse rates atop this moist boundary layer,
leading to MLCAPE values perhaps approaching 2000 J/kg (decreasing
with northward extent in Middle TN). Vertically veering wind
profiles with strong anvil-level divergence amid moderate
instability should support robust updrafts and intense supercells.
Significant tornadoes, damaging gusts and large hail will be
possible through the afternoon and spreading into AL during the
evening/nighttime hours.

Additional convection is expected to develop along an
eastward-advancing cold front during the afternoon and into the
overnight. An organized line of storms will pose a risk for damaging
wind swaths and tornadoes across northern MS/AL into TN, eastward
into GA and the western Carolinas overnight. 

...Ohio Valley...

Very strong deep-layer flow will be in place across the Ohio Valley
on Saturday with some convection possibly ongoing from southeast
Lower MI into western/central KY. The extent of severe potential is
uncertain and dependent on how much precipitation occurs early in
the forecast period. Too much convection early in the day could
largely limit destabilization and temper the overall risk. However,
if less convective contamination occurs, greater destabilization
could occur ahead of a deepening surface low lifting northeast from
the Mid-South to OH during the evening. Given the strength of
deep-layer flow at least some risk of strong/damaging gusts within
bands of thunderstorms should occur through Saturday night.

..Leitman.. 03/13/2025

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