SPC Jan 8, 2024 2000 UTC Day 1 Convective Outlook

[NorthGeorgiaWX]

SPC 2000Z Day 1 Outlook

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0159 PM CST Mon Jan 08 2024

Valid 082000Z - 091200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM PARTS OF
SOUTHEAST TEXAS INTO SOUTHERN LOUISIANA/MISSISSIPPI/ALABAMA...AND
THE WESTERN FLORIDA PANHANDLE...

...SUMMARY...
Severe thunderstorms capable of strong/damaging wind gusts and
tornadoes are expected across the Gulf Coast States this afternoon
through early Tuesday morning, spanning from southeast Texas and
southern Louisiana across southern Mississippi, southern Alabama to
the western Florida Panhandle. Strong tornadoes are possible.

...20Z Update...
The primary changes to the outlook were to trim probabilities from
the northwest to reflect the cold frontal passage, and expand
probabilities southward along the cold front into central TX, where
recent storm development has been noted within a favorable
environment.

Otherwise, the previous outlook reasoning remains valid. Parts of
southeast TX are being monitored for supercell maturation, with
potential for all severe hazards. See MCD 17 and Tornado Watch 1 for
more information regarding the short-term threats in this area. 

An extensive QLCS is still expected to develop this evening and move
eastward along the Gulf Coast, with recent HRRR runs suggesting some
potential for prefrontal supercell development. Any mature
pre-frontal supercells could pose a strong tornado threat late
tonight across parts of the central Gulf Coast, with damaging wind
and line-embedded tornadoes also possible with the primary QLCS. A
Moderate Risk upgrade remains possible with the 01Z update,
depending on observational and short-term guidance trends regarding
northward advance of the warm front and potential for mature
prefrontal supercells overnight.

..Dean.. 01/08/2024

.PREV DISCUSSION... /ISSUED 1028 AM CST Mon Jan 08 2024/

...Synopsis...
A powerful upper cyclone over the southern Plains this morning will
eject east-northeastward today, eventually reaching the lower/mid MS
Valley by early Tuesday morning. A very strong mid-level jet (around
90-110 kt) associated with this cyclone will translate eastward
across TX and the lower MS Valley through tonight. Primary surface
low over the TX Panhandle this morning is expected to develop across
OK today, and it should reach the mid MS Valley by the end of the
period. A secondary surface low should develop across
coastal/southeast TX today, and into LA and central MS by late this
evening. Low-level mass response and warm/moist advection is already
occurring in earnest across coastal TX. This trend is forecast to
continue as a surface warm front lifts northward across coastal
portions of LA/MS/AL and the FL Panhandle this evening through
tonight. A cold front attendant to the secondary surface low will
continue to sweep quickly eastward across TX and the lower MS Valley
through the period.

...North/Central Texas into ArkLaTex today...
A line of elevated convection is ongoing this morning across parts
of north/central TX along the cold front. This activity should tend
to remain elevated in the short term, but some threat for occasional
strong/gusty winds may exist this afternoon and evening as the line
moves into a gradually destabilizing airmass. Additional convection
that forms ahead of the front in a strong low-level warm advection
regime could acquire supercell characteristics given the very strong
deep-layer shear. These thunderstorms will probably pose some threat
for hail even if they remain elevated as they race
east-northeastward.

...Southeast Texas into Southwest Louisiana this afternoon and
evening...
Mid to upper 60s F surface dewpoints will become increasingly common
across southeast Texas/southwest Louisiana as a southerly low-level
jet strengthens to 50-65 kt across this area. Persistent cloud cover
and ongoing showers/thunderstorms along/north of the warm front
should limit solar heating to some extent. But, lingering MLCIN
should weaken through the afternoon as deep-layer ascent increases
and gradual warming of the boundary layer occurs. In tandem with
steeping mid-level lapse rates, 1500-2500 J/kg of MLCAPE appears
likely to develop by peak heating later this afternoon. Scattered
thunderstorms should gradually evolve/deepen as forcing for ascent
increases with the ejecting upper cyclone, coincident with strong
low-level and deep-layer shear that will easily supercells and an
increasing hail, damaging wind, and tornado risk. A few
semi-discrete storms/supercells may develop ahead of more linearly
organized storms evolving near the cold front during the afternoon
and evening. Given the strength of the low-level flow and ample
forecast effective SRH, strong tornadoes appear possible.

...Southeast Louisiana into Southern Mississippi/Alabama and the
Florida Panhandle this evening through late tonight...
Have held at Enhanced Risk with this update due to uncertainty
regarding potential for pre-frontal supercells ahead of the squall
line, mainly after 06Z tonight. Latest guidance continues to suggest
that rich low-level moisture will attempt to rapidly advect
northward in tandem with a marine warm front this evening and
tonight as a very strong (60-70+ kt) southerly low-level jet
develops over the lower MS Valley and Southeast. Elevated showers
and thunderstorms occurring in this low-level warm advection regime
may tend to hamper the inland extent of the surface warm sector to
areas along/near the coast. Even so, both low-level and deep-layer
shear appear very favorable for organized severe convection,
including the potential for tornadoes and significant damaging
winds.

Multiple rounds of severe weather will likely occur from parts of
southeast LA into southern MS/AL and the FL Panhandle beginning
later this evening, and continuing through tonight into early
Tuesday morning. The potential for surface-based supercells ahead of
the cold front is still somewhat uncertain. But, if any can form and
be sustained in the low-level warm advection regime along/south of
the warm front, they would be capable of producing strong tornadoes
given effective SRH potentially exceeding 400 m2/s2. Greater
potential for scattered to numerous damaging winds, some of which
could be significant, is apparent with an intense squall line that
will likely consolidate and strengthen as it races eastward across
southern LA/MS/AL and parts of the FL Panhandle late tonight.
Multiple embedded QLCS tornadoes, some of which could be strong
given the very favorable low-level shear, are also a distinct
possibility. Observational and guidance trends will be closely
monitored across this area for signs of increasing pre-frontal
supercell potential, which may necessitate greater tornado
probabilities in a later outlook.

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