ACUS02 KWNS 260655
SWODY2
SPC AC 260653

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1253 AM CST Tue Nov 26 2024

Valid 271200Z - 281200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE
ARKLAMISS REGION INTO CENTRAL/NORTHERN AL...

...SUMMARY...
Isolated strong to severe storms are possible from the lower
Mississippi Valley into parts of Alabama, primarily from late
Wednesday night into early Thursday morning.

...Synopsis...
A positively tilted mid/upper-level shortwave trough is expected to
move quickly eastward from the central Rockies/Great Plains toward
the lower/mid MS and TN Valleys from Monday into Monday night.
Guidance still varies regarding the timing and amplitude of this
shortwave, as well as with the strength of a surface low that is
generally forecast to move eastward across parts of the TN/OH
Valleys later in the period.

...Lower MS Valley into the TN Valley...
Low-level moisture is expected to stream northeastward from the
northwest Gulf of Mexico Wednesday afternoon into Wednesday night,
with upper 60s F dewpoints reaching southern MS, and low/mid 60s F
dewpoints extending into central/northern MS/AL. A warm layer
between 850-700 mb will tend to suppress surface-based storm
initiation through the day, though steep lapse rates above this
layer will result in MLCAPE increasing above 1000 J/kg (with
somewhat greater MUCAPE values) from LA into at least southern MS,
while MLCAPE of near 500 J/kg may reach a larger portion of AL/MS.
Notably, some guidance (such as the NAM) is much less aggressive
with the northern extent of favorable instability.

Low-level and deep-layer flow/shear are expected to become rather
strong across much of the Southeast Wednesday evening/night,
resulting in a conditionally favorable kinematic environment for
organized storms. The primary uncertainty regarding severe potential
is the coverage of deep convection within an initially capped
environment. There is some signal for initially elevated development
by late evening within a warm-advection regime, which may continue
into the overnight hours as the boundary layer moistens and
potentially better supports near-surface-based storms. Some
development will also be possible along the cold front prior to 12Z.

With strong deep-layer flow/shear and generally favorable midlevel
lapse rates expected along/ahead of the front, isolated
strong/damaging gusts and hail will be possible if deep convection
can be sustained Wednesday night. The tornado threat is more
uncertain, due to lingering MLCINH and the eventual undercutting
nature of the front, but a tornado cannot be ruled out if convection
can become near-surface-based with time.

With the GFS/GEFS and ECMWF control/ensemble suggesting some
potential for deep convection within a strongly sheared environment,
a Marginal Risk has been included for primarily late in the forecast
period. Some adjustments will likely be needed in subsequent
outlooks, depending on trends regarding shortwave amplitude and
frontal timing.

..Dean.. 11/26/2024

$$

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