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Severe WX Severe Wx Outbreak March 1st- 3rd, 2023 - Southern States, MS/OH/TN Valley

severe_ml_day5_gefso_030312.png

Yikes... big yikes.
 
BMX and FFC AFDs. Both offices keeping a close eye on this system.
.LONG TERM...
(Tuesday through Saturday)
Issued at 445 AM CST SUN FEB 26 2023

/Unsettled weather expected Wednesday through Friday; Updated
Severe Weather potential Thursday night into Friday morning/

A relatively zonal flow aloft will stretch across much of the CONUS
Tuesday morning, though a subtropical ridge will remain established
across the Caribbean. A multitude of disturbances will reside across
the northern tier of the CONUS, with a potent disturbance progged to
dig southeast across the West Coast. A cold front will position near
the I-10 corridor/Gulf Coast after having passed through Central
Alabama during the morning hours. As such, Tuesday will be a fairly
calm day weather-wise with stable conditions in the wake of the
morning frontal passage. Highs in the 70s to low 80s are forecast.

By Wednesday the pattern aloft will become a little more amplified
as the aforementioned West Coast disturbance begins a progression
toward the Desert Southwest. The front to our south is progged to
lift back to the north as a warm front during the morning hours.
Guidance continues to suggest an embedded shortwave perturbation
moving from the ArkLaTex toward the Tennessee Valley by the
afternoon. Forcing aloft will coincide with the surging warm front
to foster convection across most of the forecast area, but better
confidence exists across the northern half of the area at this time.
A scattering of showers and thunderstorms are expected by the late
afternoon, and this activity will warrant some attention as the
progged parameter space suggests the potential for a few stronger
storms. GFS/ECMWF forecast soundings show modest mid-level lapse
rates (~6.5 C/km) and 60+ kts eff. bulk shear. These westerly mid-
level flow setups this time of year tend to support a few hail
storms and/or damaging wind gusts. Will monitor trends here in case
confidence increases enough to warrant any formal messaging needs.

Either way, guidance suggests the primary area of convection will
focus along the establishing front/convergence zone near the I-40
corridor by Wednesday evening. Support aloft will advance east
thereafter, nudging the front to the southeast which will lead to a
second round of convection/rain Wednesday night into Thursday
morning. Lingering showers and a few storms will reside along the
stalling front, somewhere near I-20, into Thursday afternoon.

Meanwhile, the disturbance to our west draws closer. Guidance
suggests this potent disturbance will advance across the Southern
Plains toward the Lower Mississippi Valley by early Friday morning
supporting cyclogenesis somewhere between the Tennessee and Ohio
Valleys. Both the GFS and the ECMWF show a very powerful mid-level
jet streak approaching the Tennessee Valley Friday morning with 500
mb winds approaching 120-130 kts. A corresponding 60-70 kt low-level
jet will move east across Central Alabama Friday morning, generally
along and ahead of the advancing cold front, as the trough takes on
a more neutral tilt. This period will also need watched as the
abundance of kinematics (and dynamics aloft) will overspread
500-1,000 J/kg MLCAPE across the warm sector that morning. It
appears the ongoing band of linear-forced convection would pose a
threat of strong/severe wind gusts given the intense winds aloft
and convective mixing. Some tornadoes are also possible given low-
level shear and vector crossover. This period will also likely
contain non-thunderstorm wind gusts of 35-40 mph, enough for a
Wind Advisory. Both of these threats are now in the HWO.
Click to expand...
.LONG TERM...
(Monday night through Saturday)
Issued at 414 AM EST Sun Feb 26 2023

By Monday night, frontogenetic forcing should continue to weaken
across central GA. This combined with drier mid levels across
central GA and a diminishing thermodynamic environment will mean
only slight chance of showers/thunderstorms in East GA. A few
lingering showers may be possible for west-central GA Tuesday
morning, as things clear out further.

Tuesday and Wednesday conditions look mostly warm, clear, and dry.
Max temperatures will be in the mid to upper 70s with lows in the
upper 40s and 50s. Winds may be a little breezy Tuesday morning,
however this should taper off through the day.

Wednesday afternoon sees the return of our active pattern as models
open the GoM again ahead of the next shortwave system. This
shortwave should begin making its way across the Southeast on
Friday, however precipitation along the warm front will mean showers
and thunderstorms for North, and parts of Central, GA Wednesday and
Thursday. With the current southward track of the shortwave, upper-
level support, deep moisture (PWATS ~1.5"), and abundant shear (srh
over 400 m2/s2), we could support strong to severe high-shear/low-
CAPE thunderstorms. Model uncertainty as to the timing of the
frontal passage has decreased since yesterday, however we will
definitely need to keep an eye on this system as we get closer. Once
this next system moves out, we may have a short opportunity to dry
out a cool off, Yippee!
Click to expand...
 
Yep. If current trends continue, and I hesitate to say this at this range, we would be looking at a High risk level event. Interested to see if UKMET and ECM begin to fully agree - I think if they do we could be looking at a Day 3 Mod.

Edit: UKMET on board.
 
UncleJuJu98 said:
SPC mentions a widespread outbreak is possible, seriously feels like easter 2020 with such a widespread west to east movement. View attachment 18205
Click to expand...
I am still skeptical that the D5 “ceiling” will verify, at least tornado-wise. The past five runs of the EPS have been gradually trending toward a higher-amplitude trough with less directional shear. Each run shows a narrower and narrower wavelength. The background suggests that the mid-level trough may begin to occlude by late afternoon, if not sooner. Also, the trough isn’t negatively tilted during peak diurnal heating. I think the potential for a widespread damaging-wind event is much more likely than a significant tornado outbreak. It should still be watched closely, but on account of severe winds rather than EF2+ tornado families. People should definitely not ignore damaging winds. At this rate a fairly robust QLCS is likely.
 
We're getting a bit more consistency it seems, members had really been struggling on the exact timing and placement, but for sure looks like a major regional damaging wind threat incoming. March, as they say, coming in like a lion this year.
 
Casuarina Head said:
I am still skeptical that the D5 “ceiling” will verify, at least tornado-wise. The past five runs of the EPS have been gradually trending toward a higher-amplitude trough with less directional shear. Each run shows a narrower and narrower wavelength. The background suggests that the mid-level trough may begin to occlude by late afternoon, if not sooner. Also, the trough isn’t negatively tilted during peak diurnal heating. I think the potential for a widespread damaging-wind event is much more likely than a significant tornado outbreak. It should still be watched closely, but on account of severe winds rather than EF2+ tornado families. People should definitely not ignore damaging winds.
Click to expand...
I am interested as to how this plays out, as what you have said previously this year has all been pretty accurate.

But firstly, I don't know if this trend is an actual trend from the model suite to a much more amplified trough or just a reflection of more ensemble members agreeing on one solution, which given it is Day 5 seems perhaps like that could be the culprit - and even then the trend is relatively negligible as seen here, and even taking on a more favourable trough shape if anything

trend-epsens-2023022600-f120.500wh-mean.conus.gif
Even then, if we were to have a higher amplitude event, I don't think this would necessarily lower the ceiling as much as you suggest. GFS is more amplified than the ECM is and the GFS has a large open warm sector extending up towards TN.

This leads me to my next point: We have decent moisture sitting across the S states before the event and so we have a large forecast warm sector which makes sense. At this stage the forecast is not for a pinched of warm sector like last March where the main threat was just QLCS tornadoes - which did cause significant outbreaks in both cases, even if they were not 'multiple strong tornado families' as you seem to define significant outbreaks by.

At least on GFS and now increasingly other models, the favourable environment is already in place from TX/OK by 21z and continues through the late afternoon and evening further East. We will still have elevated CAPE from daytime heating and as we know from Dec 2021 later afternoon and evening events do not preclude discrete supercells with violent tornadoes. Roughly eyeballing forcing from the GFS - we still have broad but not excessive large scale ascent over the large open warm sector.

So basically as it appears to me, we will almost always be able to find at least small issues with setups which you have highlighted. Yet for this range, and the model trends and agreements over the last day or so are painting a picture of at least synoptically a pretty favourable set up - one of the most favourable since at least 2021. Of course you may be completely right and I will gladly accept being completely wrong, but if trends stay consistent, I think this event is pretty concerning at this stage.
 
The environment for tornadoes if isolated convection forms over the Louisiana Arkansas Mississippi area is maddening. When looking at the GFS and it's win profiles. High risk definetly on the table for that area. Especially if the low doesn't occlude as early as predicted. A very dangerous event is on the table moving forward if the event moves forward as current thinking goes. Screenshot_2023-02-26-11-56-11-86_40deb401b9ffe8e1df2f1cc5ba480b12.jpgScreenshot_2023-02-26-11-55-50-06_40deb401b9ffe8e1df2f1cc5ba480b12.jpgScreenshot_2023-02-26-11-55-57-84_40deb401b9ffe8e1df2f1cc5ba480b12.jpgScreenshot_2023-02-26-11-55-36-39_40deb401b9ffe8e1df2f1cc5ba480b12.jpgScreenshot_2023-02-26-12-00-58-98_40deb401b9ffe8e1df2f1cc5ba480b12.jpgScreenshot_2023-02-26-12-02-25-94_40deb401b9ffe8e1df2f1cc5ba480b12.jpg
 
Last edited:
Hate to say it, but parameters will likely be off the charts for portions of areas west of Alabama when mesoscale models come in. A very dangerous event is likely to unfold if models continue.

You never go almost off the charts on globals and not have mesoscale models ramp up things more

I really hope meteorlgists start chiming in. I imagine they will once todays big event ends over the plains.
 
Casuarina Head said:
I am still skeptical that the D5 “ceiling” will verify, at least tornado-wise. The past five runs of the EPS have been gradually trending toward a higher-amplitude trough with less directional shear. Each run shows a narrower and narrower wavelength. The background suggests that the mid-level trough may begin to occlude by late afternoon, if not sooner. Also, the trough isn’t negatively tilted during peak diurnal heating. I think the potential for a widespread damaging-wind event is much more likely than a significant tornado outbreak. It should still be watched closely, but on account of severe winds rather than EF2+ tornado families. People should definitely not ignore damaging winds. At this rate a fairly robust QLCS is likely.
Click to expand...
Yeah tornado threat don’t look that high be honest… but a serious wind threat sure looks likely this far
 
Taylor Campbell said:
Model data has gone full tilt on the severity of this system. Major tornado outbreak.
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The GFS definitely has. I would be much more concerned about the ECMWF, and only within forty-eight hours of the event. If there were a solid consensus of the GFS+EC+UK showing a similar UA setup within this range (D2 or less), then I would definitely be sounding the alarm about a full-spectrum event, including a significant tornado outbreak, rather than just a severe wind-driven event. At this point I am still skeptical that the UL pattern will look similar once we get within a few days of the event. The kinematics will definitely be strong, but whether they will favour discrete vs. linear mode is an open question. At this point I am strongly favouring linear vs. discrete, hence a major QLCS and severe wind vs. multiple (two or more) EF2+ tornado families. But I am willing to change if trends hold within a few days of the event.
 
tennessee storm chaser said:
Yeah tornado threat don’t look that high be honest… but a serious wind threat sure looks likely this far
Click to expand...
Can't say that yet, don't focus on that , mesoscale models will probably determine that. Just know a significant weather event is possible moving forward as we get closer a more details on the threat will be uncovered. Looks at the wind spreads a tornado outbreak is extremely possible.
 
UncleJuJu98 said:
Can't say that yet, don't focus on that , mesoscale models will probably determine that. Just know a significant weather event is possible moving forward as we get closer a more details on the threat will be uncovered. Looks at the wind spreads a tornado outbreak is extremely possible.
Click to expand...
Sure anxious see the 12z euro … waiting anxiously
 
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