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Severe Weather Threat - January 8th-9th, 2024

Most of the CAMs advertising at least some supercell threat along the coast tomorrow night into Tuesday. Could be a potent day along the Gulf Coast from LA to FL. Also, the ARW has a wicked supercell that lasts forever over the water.
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CheeselandSkies said:
Tough forecast for the SPC for sure. The surface to 500mb synoptic setup is about as classic as it gets, with a high-end parameter space in terms of kinematics, but there are legitimate questions on where/when and to what extent the favorable thermodynamics will overlap.
Click to expand...
Absolutely. Just looking at the RRFS 12z run shows supercell heaven in South Alabama but can't tell wether it's elevated or surface based, right along the warm front it seems.

I think a lot of spin ups will be possible either way if there isn't a bunch of supercells.
 
.THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS THE
CENTRAL GULF COAST OVERNIGHT MONDAY INTO EARLY TUESDAY...

...SUMMARY...
Severe thunderstorms capable of strong wind gusts and tornadoes are
expected from southeast Texas across the central Gulf Coast and from
Monday afternoon into early Tuesday morning. Greatest severe
potential is anticipated overnight from southeast Louisiana across
southern Mississippi and southern Alabama, and into the western
Florida Panhandle.

...Synopsis...
Shortwave trough currently extending from Great Basin through the
northern Baja Peninsula is forecast to move eastward today while
intensifying. By 12Z Monday morning this shortwave will likely have
matured into a mid-latitude cyclone centered over northeast NM, with
an extensive belt of strong mid-level flow throughout its southern
periphery. This cyclone is then expected to evolve eastward across
the TX Panhandle and OK throughout the day, with mid-level flow
strengthening considerably throughout its eastern periphery. By
Monday evening, 100+ kt at 500-mb will likely stretch from the
Edwards Plateau into the Ozark Plateau. Further strengthening of
this mid-level flow is anticipated overnight Monday as the cyclone
tracks a bit more northeastward, ending the period over western MO.
Intense low-level flow will accompany this cyclone as well, with a
large area of 50+ kt over the southern Plains early Monday. This
low-level jet will shift eastward throughout the day and overnight,
while gradually strengthening. By early Tuesday morning, 60+ kt
850-mb flow will cover much of the Southeast, with 70+ kt possible
from northern MS into middle TN and northern AL.

Previous frontal intrusion (evidenced by the cold and dry conditions
over the southern Plains and Southeast Sunday) will limit the
northern extent of the moisture return and associated
severe-thunderstorm potential. General expectation is for secondary
surface cyclogenesis over central TX Monday morning, with the
primary low well to the north over the TX/OK Panhandles. This
secondary low (and associated warm front) should delineate the
northern extent of the severe potential as it gradually moves
eastward across central portions of east TX and into central LA
Monday afternoon and evening. This low is forecast to continue
eastward overnight Monday into early Tuesday, progressing across
central MS and AL. Severe thunderstorms are expected within the warm
sector ahead of this low, as well as along the associated cold front
as it surges eastward.

...North TX Early Monday...
As the strong mid-level flow associated with the cyclone moves into
southern Plains, a fast-moving line of showers and embedded
thunderstorms is expected to move across north TX early Monday
morning. Forecast soundings show very weak thermodynamics, limiting
overall updraft strength and duration. However, given the strong low
and upper level support, a narrow-line of forced convection may
become capable of locally gusty/damaging wind gusts as it moves
eastward.

...TX Coastal Plain/Southeast TX into southwest LA Monday Afternoon
and Evening...
Two rounds of strong to severe thunderstorms are possible across the
region Monday, with the first round likely beginning early Monday
afternoon as the warm sector moves into the region. Current guidance
suggests this warm sector will be characterized by temperatures in
the low 70s, dewpoints in the upper 60s, and moderate buoyancy.
However, given the prevalence of cloud cover and early period
showers, there is uncertainty regarding if temperatures can reach
the low 70s. If they do, some surface-based supercells capable of
all severe hazards, including tornadoes are possible. If
temperatures stay in the 60s, low-level stability would likely
inhibit surface-based storm development, mitigating the severe
potential. Consensus within the guidance has trended towards warmer
temperatures and tornado probabilities were increased across the
region as a result. A further increase in probabilities may be
needed in later outlooks if confidence in surface-based storms
increases.

Additional thunderstorm development is anticipated along the front
as it moves through, but the strength of these storms will be
predicated on coverage and strength of any warm sector development.
Strong wind gusts would be the primary severe risk with this
convective line.

...Central Gulf Coast Overnight Monday into Tuesday Morning...
As the surface low continues eastward, a convective line is expected
to mature along the cold front as it encounters a moderately moist
and buoyant airmass and increasingly strong low-level flow. As the
line matures, it will likely transition from a more parallel
stratiform structure to a more organized leading-line, trailing
stratiform configuration. Robust low-level kinematics, characterized
by 50-60 kt just above the surface and 500+ m2/s2 of 0-3 km SRH,
suggest both significant-severe gusts and strong QLCS tornadoes are
possible.
Click to expand...



SPCTOR.jpg
 
Disco from the rare D3 update (not including prev. disco)
...SUMMARY...
Strong to severe thunderstorms may impact much of the eastern Gulf
and southern Atlantic Coast states Tuesday, accompanied by a risk
for damaging wind gusts and tornadoes.

...FL Panhandle/Southeast AL/Southern GA Tuesday morning...
General expectation is that a fast-moving, well-organized convective
line will be ongoing at the beginning of the period across the
western FL Panhandle and southeast AL. Robust kinematic fields
suggest that strong gusts are likely within this line. Additionally,
large, looping low-level hodographs indicate there is possibility
for line-embedded QLCS tornadoes as well. With the mid-latitude
cyclone (and associated large-scale ascent) becoming increasingly
displaced to the north, relatively warm mid-level temperatures
downstream across northern FL and southern GA are currently expected
to lead to some decrease in the intensity of the line as it
continues eastward.

...Coastal/Central Carolinas...
As the system becomes negatively tilted, strong low-level moisture
advection is anticipated ahead of the approaching cold front and
associated convective line. This increase in low-level moisture will
likely be accompanied by widespread cloud cover and showers,
limiting diurnal heating. As a result, despite increasing low-level
moisture, the combination of limited heating and relatively warm
mid-level temperatures could stunt overall buoyancy and updraft
strength.
Click to expand...
 
SPC seems to be hinting at Moderate Risk potential too:

"If temperatures stay in the 60s, low-level stability would likely
inhibit surface-based storm development, mitigating the severe
potential. Consensus within the guidance has trended towards warmer
temperatures and tornado probabilities were increased across the
region as a result. A further increase in probabilities may be
needed in later outlooks if confidence in surface-based storms
increases."
 
JPWX said:
SPC seems to be hinting at Moderate Risk potential too:

"If temperatures stay in the 60s, low-level stability would likely
inhibit surface-based storm development, mitigating the severe
potential. Consensus within the guidance has trended towards warmer
temperatures and tornado probabilities were increased across the
region as a result. A further increase in probabilities may be
needed in later outlooks if confidence in surface-based storms
increases."
Click to expand...
When was the last MDT or higher where the primary threat was forecasted to be during the overnight hours?
 
From NWS MEG (Memphis) morning discussion:

"The surface low will track ENE across the Arkansas and Missouri
border through Tuesday morning. As the surface continues to
deepen, a tight 10mb pressure gradient will setup along and east
of the Mississippi River Monday night. All guidance points to a
3 to 6 hour window Monday night with wind gusts pushing the 50
mph mark. The only question is whether or not those winds will be
realized due to a rain-stabilizing boundary layer. Some thought
was given to a High Wind Watch, but enough uncertainty remains to
forgo it for now and continue to use probabilistic messaging. If
high winds are realized, power outages and structure damage will
be possible."

The last time that MEG issued a High Wind Watch for any portion of the Mid-South region was in December 2009.
 
TH2002 said:
When was the last MDT or higher where the primary threat was forecasted to be during the overnight hours?
Click to expand...
December 10th, 2021 comes to mind.
 
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