ACUS02 KWNS 170632
SWODY2
SPC AC 170631

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1231 AM CST Tue Dec 17 2024

Valid 181200Z - 191200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms are possible from the lower Ohio Valley southwest into
northeast/central Texas early on Wednesday and across the Southeast,
Carolinas, and Florida Wednesday afternoon and evening.

...Synopsis...

A positively tilted upper trough will develop east across the
eastern U.S. on Wednesday. Moderate mid/upper level southwesterly
flow ahead of the trough will overspread the OH/TN Valleys into the
Carolinas and Mid-Atlantic regions. At the surface, a cold front
will extend from southern OH to southeast AR to central TX at the
beginning of the period. This front will develop southeast across
the Southeast and Mid-Atlantic, mostly moving offshore from the Gulf
and Atlantic coasts by Thursday morning.

...Northeast TX to the TN Valley...

Showers and elevated thunderstorms will likely be ongoing near the
surface cold front Wednesday morning. Forecast soundings show poor
low-level lapse rates and little surface-based instability. However,
up to 500 J/kg MUCAPE will be present, courtesy of cool midlevel
temperatures and modest midlevel lapse rates. Deep-layer flow is
forecast to remain mostly unidirectional and parallel to the front,
suggesting convective undercutting by the boundary/outflows. While
some briefly organized structure may persist the first hour or two
of the forecast period, convection is expected to rapidly decrease
in intensity with southeast extent across the TN Valley/Gulf Coast
states. This is largely due to more modest boundary-layer moisture
and weakening vertical shear across MS/AL.

...FL/GA/Carolinas...

Isentropic ascent ahead of the approaching upper trough/surface
front will increase across the region through day. However,
large-scale ascent will remain weak until late, with the vorticity
maxima trailing well behind the surface front. Nevertheless, showers
and isolated thunderstorms will be possible within the low-level
warm-advection regime, especially during the afternoon/early
evening. Forecast guidance varies in the depiction of the low-level
thermodynamics and degree of destabilization. Though some support
for an organized storm or two is plausible, given around 750-1000
J/kg MLCAPE and effective shear magnitudes around 20-30 kt. While a
strong storm could produce gusty winds or even small hail (given
somewhat elongated/straight hodographs and cool midlevel temps),
forecast confidence regarding severe potential remains fairly low.
Will refrain from introducing low-end/Marginal (level 1 of 5) risk
probabilities at this time, though an outlook area may be required
in subsequent outlooks.

..Leitman.. 12/17/2024

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