SPC AC 130729

   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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