2/15/25 SE Severe Threat

...Day 4/Saturday...
Model guidance continues to forecast a strong upper-level trough
moving through the southern Plains and into the Southeast. Some
modest slowing of the trough has been noted, however. The trough
will promote the deepening of the surface low in the ArkLaTex
vicinity during the afternoon with further deepening expected into
the evening as it generally progresses north-northeastward within
the Mid-South/Ohio Valley. Moisture return will have begun Friday
evening and will continue Saturday. Guidance shows a consistent
signal for mid 60s F dewpoints extending into much of
Louisiana/Mississippi, and Alabama. Upper 60s F dewpoints are
possible closer to the Gulf Coast. Very strong wind fields are
anticipated throughout the troposphere. Shear will be strong and,
despite more modest mid-level lapse rates, buoyancy will be more
than adequate for severe storms. The current expectation is for warm
advection precipitation to be ongoing early in the period and for it
not to make much, if any, southward progress until the late
afternoon. A Pacific front in East Texas/Sabine Valley into the
ArkLaTex may be the initial zone for stronger convective
development. By the late afternoon onward, the cold front will begin
to surge south and east. The low-level jet should remain strong into
the afternoon and then increase to 50-70 kts during the evening. As
the cold front surges, shear vectors will acquire a greater
cross-boundary component. This strongly forced line will be capable
of scattered to widespread damaging winds along with the threat for
embedded circulations/QLCS tornadoes. One of the main questions that
remain will be the degree of the tornado threat, which would
increase with any discrete activity ahead of the cold front. Given
the weak capping and strong forcing, pre-frontal discrete storms are
plausible. The ECMWF shows some hint of this from central Louisiana
into adjacent Mississippi. The eastern and northern extent of the
greatest severe threat are also in question, but the intense
low-level jet could produce severe-caliber gusts even with
relatively shallow convection. The overall pattern, along with
signals in both deterministic and ML guidance, suggest 30% severe
probabilities are warranted for Saturday.
 
MichelleH said:
...Day 4/Saturday...
Model guidance continues to forecast a strong upper-level trough
moving through the southern Plains and into the Southeast. Some
modest slowing of the trough has been noted, however. The trough
will promote the deepening of the surface low in the ArkLaTex
vicinity during the afternoon with further deepening expected into
the evening as it generally progresses north-northeastward within
the Mid-South/Ohio Valley. Moisture return will have begun Friday
evening and will continue Saturday. Guidance shows a consistent
signal for mid 60s F dewpoints extending into much of
Louisiana/Mississippi, and Alabama. Upper 60s F dewpoints are
possible closer to the Gulf Coast. Very strong wind fields are
anticipated throughout the troposphere. Shear will be strong and,
despite more modest mid-level lapse rates, buoyancy will be more
than adequate for severe storms. The current expectation is for warm
advection precipitation to be ongoing early in the period and for it
not to make much, if any, southward progress until the late
afternoon. A Pacific front in East Texas/Sabine Valley into the
ArkLaTex may be the initial zone for stronger convective
development. By the late afternoon onward, the cold front will begin
to surge south and east. The low-level jet should remain strong into
the afternoon and then increase to 50-70 kts during the evening. As
the cold front surges, shear vectors will acquire a greater
cross-boundary component. This strongly forced line will be capable
of scattered to widespread damaging winds along with the threat for
embedded circulations/QLCS tornadoes. One of the main questions that
remain will be the degree of the tornado threat, which would
increase with any discrete activity ahead of the cold front. Given
the weak capping and strong forcing, pre-frontal discrete storms are
plausible. The ECMWF shows some hint of this from central Louisiana
into adjacent Mississippi. The eastern and northern extent of the
greatest severe threat are also in question, but the intense
low-level jet could produce severe-caliber gusts even with
relatively shallow convection. The overall pattern, along with
signals in both deterministic and ML guidance, suggest 30% severe
probabilities are warranted for Saturday.
Click to expand...
That's the big question. The discreet convection lol. Should have a better idea tommorow I would think, maybe even later today.
 
CheeselandSkies said:
First sniff of NAM range isn't quite as impressive I was expecting. Fairly small unstable sector Saturday afternoon/evening, right along the MS river into western Mississippi. The environment within that confined area would certainly be supportive of strong tornadoes, though.
Click to expand...
Wouldn't take it at face value (at the end of its range, anyway) as it seems to frequently underdo thermals, particularly in the cold season. GFS has max temps a few degrees warmer during the day Saturday, for example. That said, warm sector may be constrained by the progress of the front, which may limit the potential for pre-frontal discrete activity, especially with eastward extent.
 
I sometimes think its a bit overkill to analyse every single trend on every model run - but at this range it feels like all we can really do! That being said, I am quite liking the trend on the NAM and a couple other models in terms of reducing the severe risk, with a reduction in the trough's amplification. Will have to continue to watch the models over the next few days though, of course.
1739392896562.png
 
UK_EF4 said:
I sometimes think its a bit overkill to analyse every single trend on every model run - but at this range it feels like all we can really do! That being said, I am quite liking the trend on the NAM and a couple other models in terms of reducing the severe risk, with a reduction in the trough's amplification. Will have to continue to watch the models over the next few days though, of course.
View attachment 33632
Click to expand...
It does look less clean, although I've noticed that at this range, models have a tendency to wobble on synoptics, and trough shape is one of those things that tends to vary. Of course, I do hope to see this trend continue, as the overall posture of this setup has me feeling uncomfortable.
 
I'm seeing nothing that would convince me of a downtrend in Saturday's threat. The only biggest question is overall extent of the tornado threat which is dependent upon the unknown mesoscale factors.
 
JPWX said:
I'm seeing nothing that would convince me of a downtrend in Saturday's threat. The only biggest question is overall extent of the tornado threat which is dependent upon the unknown mesoscale factors.
Click to expand...
I mostly have questions about convective intensity with eastward extent. Threat for most of MS and much of AL seems relatively unambiguous to me - large overlap of favorable thermodynamics and very robust kinematics.
1739400335025.png1739400351958.png
 
TornadoFan17 said:
I think ArkLaMiss into central MS will be the primary area of concern for Saturday.

If you asked me right now, I'd say I think the SPC gives that area a 15% hatched MDT by the D1 outlook.
Click to expand...
The last thing Mississippi needs is more tornadoes. Praying it doesn’t become a major outbreak.
 
New D3 outlook


Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0230 AM CST Thu Feb 13 2025

Valid 151200Z - 161200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FOR PARTS OF
THE LOWER MISSISSIPPI VALLEY AND WESTERN ALABAMA...

...SUMMARY...
Severe weather is expected from East Texas into much of the
Southeast and parts of the Mid-South on Saturday. Scattered to
numerous damaging wind gusts and a few tornadoes are the primary
threats. Storms are expected from late afternoon through the
evening.

...Synopsis...
A potent upper-level trough initially within the Four Corners will
make quick progress through the Southern Plains and into the lower
Mississippi Valley on Saturday. A surface low in the southern Plains
will track into the Mid-South and eventually the Ohio Valley, all
the while deepening. A cold front will move through the Southeast
beginning in the late afternoon into Sunday morning. Intense wind
fields are expected with ample low-level and deep-layer shear.

...Southeast...
Precipitation will likely be ongoing within a zone of warm advection
from the Ozarks into the Mid-South vicinity. This activity will have
an impact on the exact extent of northward moisture advection and
destabilization. The deepening surface low should push some of this
activity northward during the day, however. Models are in general
agreement that a fairly broad warm sector will remain precipitation
free during much of the morning and early afternoon. Temperatures
across the warm sector within the mid/upper 70s F appear probable.
One of the main sources of uncertainty will be whether afternoon
convection can develop in the warm sector. The ECMWF continues to
hint at this possibility while the cooler surface temperatures in
the NAM limit destabilization. Storms during the afternoon would
likely be discrete and there would be an increase in the tornado
threat, some of which could be strong. By the late afternoon into
the evening, there is high confidence in the cold front beginning to
surge south and east. This will coincide with an intensification of
the low-level jet. Strong to significant wind gusts would be
possible as would QLCS tornadoes. With northward and eastward
extent, buoyancy should lessen. However, the 50-65 kt low-level jet
would promote a risk of damaging surface gusts even with more
muted/shallow convection.

...East Texas/Sabine Valley...
A Pacific front will be draped across the region, south of the
parent surface low. Uncertainty in storm development in this area is
slightly higher than farther east. Strong shear across this boundary
would support organized storms, most likely supercellular initially.
Damaging winds and tornadoes would be possible. Given the closer
proximity to steeper mid-level lapse rates, large hail could also
occur. With time and increased mid-level ascent, activity would
likely congeal into a line later in the afternoon.

..Wendt.. 02/13/2025
 

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