SPC Dec 8, 2023 0700 UTC Day 2 Convective Outlook

[NorthGeorgiaWX]

SPC 0700Z Day 2 Outlook

Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1256 AM CST Fri Dec 08 2023

Valid 091200Z - 101200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM EAST TX TO
THE TN VALLEY...

...SUMMARY...
Scattered severe thunderstorms with tornadoes, damaging winds, and
large hail will be possible from east Texas to the Tennessee Valley,
mainly Saturday afternoon and evening.

...Synopsis...
A leading cyclogenetic surface low will quickly move from the Lake
MI area at 12Z Saturday towards James Bay. As this occurs, the cold
front trailing to its south-southwest will initially decelerate over
the south-central states, downstream of a basal shortwave impulse.
This feature should advance from the NM vicinity to the Ark-La-Tex
by 12Z Sunday. Much weaker secondary cyclogenesis is anticipated
ahead of this latter wave from the Ark-La-Tex to the TN Valley. 

...East TX to the TN Valley...
While regional/global guidance has converged towards a consensus on
the upper-level synoptic pattern, differences emerge in
timing/placement of the surface baroclinic zone. In addition, CAM
guidance offers quite a bit of spread with the potential convective
evolution on Saturday. As a result, primary change has been to
expand the northeast extent of severe probabilities within a
conditionally favorable, high-shear/low-CAPE environment.

From east TX into south AR and west MS, a plume of moderate buoyancy
characterized by MLCAPE of 1000-2000 J/kg will become established as
surface temperatures rise into the 70s, amid dew points from the mid
to upper 60s. Increasing mid-level height falls will overspread the
aforementioned baroclinic zone midday, with convective development
along/north of the surface front initially probable near the weak
cyclone in the Ark-La-Tex. This should become more widespread to the
east and south during the afternoon, although spread in CAM guidance
is above average with just how quickly this actually occurs and the
southward extent of convective development in east TX/west LA during
the afternoon. Despite these differences, strong southwesterly
deep-layer shear will be favorable for supercells producing large
hail, especially where flow can be semi-orthogonal to the front
across east TX and the Sabine Valley. A clustered convective mode
should dominate to the east across the Mid-South owing to
orientation of convective development near/ahead of the cold front
more closely paralleling the deep-layer shear vector. But embedded
supercells are expected as well, with low-level hodographs
adequately enlarged for a few tornadoes. 

By late afternoon to early evening, an extensive swath of clusters
and line segments should dominate. Some increase in low-level SRH is
anticipated during this time frame, focused on central to north
portions of MS/AL and northward. This should foster a continued
damaging-wind and embedded tornado threat east of the MS Valley even
as convection outpaces/overturns the instability plume.
Low-probability wind/tornado threats will probably persist overnight
but should gradually wane in time.

..Grams.. 12/08/2023

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