March 30th & 31st Severe Weather for Southern Plains & Dixie Alley, Very Dangerous Nighttime Outbreak ongoing in Alabama

[Iceresistance]

The GFS has been abnormally consistent with this storm, & Mike Ventrice has his concerning forecast for those areas March 29th & 30th. 

 

Some models are having trouble with the exact dates, but there is strong consistency of the event ending on March 30th, so I've put down March 27th-30th until we get a better visual on this.

[Tallis Rockwell]

4 hours ago, Iceresistance said:

The GFS has been abnormally consistent with this storm, & Mike Ventrice has his concerning forecast for those areas March 29th & 30th. 

 

Some models are having trouble with the exact dates, but there is strong consistency of the event ending on March 30th, so I've put down March 27th-30th until we get a better visual on this.

You beat me by 4 hours...

[Chreeyiss]

Not that it really matters this far out, but despite the relative consistency in the gfs (cmc and euro have been all over the place), I see some things that are far from being nailed down:

- Timing: looks like overnight Tue-Wed (though gfs tends to be too progressive, might this eventually turn into a Wed event for the plains?)

- 500mb pattern: Will there be a northern lobe and associated surface low in Kansas and Nebraska, as shown on some runs, or will the southern lobe in NW Texas remain dominant?

- Will the low level jet sync sufficiently with the upper levels and create a favorable shear profile, and if so, where? (imagine this is a function of the 2 points above)

First thing that comes to mind for me looking over these runs, at least for Texas and Oklahoma, is an overnight MCS. If shear and instability are sufficient, maybe there would be an embedded supercell/tornado risk. 0z GFS run doesnt really maximize either of these though. Of course, all of this is speculation on my part for entertainment purposes and an attempt to see if I've learned anything at all over time regarding pattern recognition. It also makes the lofty assumption that the GFS is onto something to begin with.  Guess we'll see. 

[Iceresistance]

Ventrice has this (Treating the forecast with a grain of salt)

 

 

[Iceresistance]

Already a potential rainmaker for the Southern Plains

[CheeselandSkies]

15 minutes ago, Iceresistance said:

Already a potential rainmaker for the Southern Plains

Much needed...hope it verifies. As bad as the western drought is, the further east it extends is even worse for chaseable weather.

[Iceresistance]

More consistency with the models to have it start the Severe Weather setups on the 29th, even the WPC is showing good rainfall for the Southern Plains on the 30th as well.

[Iceresistance]

SPC introduces Slight Risks on D5 & D6. 

D5 is a classic setup for the Great Plains.

While D6 is a Dixie Alley setup.

[CheeselandSkies]

00Z and 06Z GFS have rather paltry instability throughout the warm sector despite upper 50s dewpoints all the way to southern Wisconsin (equal to or greater moisture as the model was forecasting to reach this latitude on March 5th at this range). That's probably a factor of the sheer amount of convection the model breaks out.

This trough appears to have some of the same issues as the last one, mainly very meridional (SSW to even southerly or SSE) 500mb flow which is parallel to the initiating boundary (cold front) which often makes for a messy convective mode in which it's hard to get long-lived, discrete tornadic supercells. That said, there will probably be significant severe weather somewhere as with the last system.

[yoda]

Day 4-8 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0359 AM CDT Sat Mar 26 2022

   Valid 291200Z - 031200Z

   ...DISCUSSION...
   Medium-range model guidance remains in good agreement that a
   shortwave trough will move through the Southwest into the southern
   Plains on D4/Tuesday, before then trending towards a more negative
   tilt while moving through the Lower/Mid MS Valley and into the OH
   and TN Valley on D5/Wednesday. This shortwave is then forecast to
   continue northeastward through the Mid-Atlantic on D6/Thursday.

   Severe potential will accompany this shortwave as it progresses
   eastward, beginning across the southern and central Plains on
   D4/Tuesday. Strong moisture advection will precede the shortwave
   across the Plains, with low 60s dewpoints potentially reaching
   through eastern OK by Tuesday evening. A well-developed EML atop
   this returning moisture will support moderate buoyancy. A sharp
   dryline will intersect with this buoyancy to support thunderstorm
   development, with the mesoscale ascent along the dryline aided by
   strengthening large-scale ascent. Supercell wind profiles will
   support updraft organization and the potential for all severe
   hazards.

   The severe weather threat will continue into the Lower/Mid MS Valley
   on D5/Wednesday. Buoyancy will be weaker here than farther west on
   D4/Tuesday, but both low- and mid-level flow will be very strong.
   Current guidance suggests mid-level flow within the now negatively
   tilted trough will exceed 100 kt at 500 mb. A large area of 60-65 kt
   850 mb winds is expected. This will result in large, looping
   hodographs that support organized severe thunderstorms. Convective
   mode will have a large influence on the dominant severe type, but a
   discrete mode would result in the potential for long-lived
   supercells. Even if the mode is more linear (which appears most
   likely at this point), the strong wind fields support the potential
   for numerous severe gusts as well as embedded QLCS circulations.

   The shortwave will likely lose some definition by D6/Thursday but
   remain strong enough to support thunderstorms as it interacts with
   the moderately moist and buoyant environment across the
   Mid-Atlantic. Strong wind fields are expected to support organized
   severe thunderstorms across portions of central VA and central NC.

   Variability (both run to run and between models) increases after
   D6/Thursday, limiting forecast confidence and predictability on
   D7/Friday and D8/Saturday.

   ..Mosier.. 03/26/2022

[Iceresistance]

D4 is a very large Slight Risk, D5 is now Enhanced.

[CryHavoc]

SLGT issued for D3.

Given the modest early season moisture quality, the warm-sector air mass is unlikely to be overly unstable coincident with initial deep convective development, with MLCAPE likely to limited to 750-1250 J/kg across parts of eastern Kansas into Oklahoma and north Texas. However, strong wind profiles should support some initial supercells and an evolving/mixed convective mode during the evening. Large hail and damaging winds can be expected across the region. A couple of tornadoes could also occur, perhaps especially in vicinity of the surface low/triple point across eastern Kansas and nearby Lower Missouri Valley, and/or across Oklahoma/east Texas and nearby ArkLaTex region coincident with a strengthening low-level jet Tuesday night.

Seems reasonable. Definitely still worth watching.

[Iceresistance]

BIG Enhanced risk in place for Dixie Alley on D4, very strong wording from the SPC

 ...SEVERE WEATHER OUTBREAK POSSIBLE ON D4/WED...

   ...DISCUSSION...
   An appreciable severe-weather risk appears increasingly likely
   across the Lower Mississippi Valley and Middle Gulf Coast region on
   Wednesday/Day 4. This includes the potential for widespread damaging
   winds and tornadoes, including the possibility of a regional tornado
   outbreak including strong (EF2+) tornadoes.

 

[Iceresistance]

Slight Risk extended into Missouri, there's an update for it at 12:30 PM CDT. 

The SPC is thinking it's going to become linear very quickly.

 

And here's the new D3 Severe Weather Forecast

[yoda]

Well that escalated quickly

Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1254 AM CDT Tue Mar 29 2022

   Valid 301200Z - 311200Z

   ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
   OF LOUISIANA...MISSISSIPPI...AND ALABAMA...

   ...SUMMARY...
   A regional outbreak of severe thunderstorms is expected on Wednesday
   across the Lower Mississippi Valley and Southeast States. All severe
   hazards are possible, including significant gusts over 75 mph and
   strong (EF2+) tornadoes.

   ...SEVERE-WEATHER OUTBREAK POSSIBLE ACROSS PORTIONS OF
   LOUISIANA...MISSISSIPPI...AND ALABAMA...

   ...Synopsis...
   A strong southern-stream shortwave trough is forecast to extend from
   central KS through the TX Hill Country early Wednesday morning. This
   shortwave is expected to progress eastward/northeastward throughout
   the day, becoming increasingly negatively tilted as it does. Strong
   mid-level flow will accompany this through, with 100+ kt at 500 mb
   stretching from southeast TX northeastward through the Mid-South
   Wednesday afternoon. Additionally, very strong low-level flow will
   precede this feature, with a large area of 60+ kt at 850 mb expected
   across the MS Valley Wednesday afternoon.

   Low-level moisture advection will also precede this shortwave
   trough, bringing at least low 60s dewpoints through the Mid-South/TN
   Valley. Upper 50s dewpoints will likely reach into the Lower/Middle
   OH Valley. These dewpoints will help foster at least modest buoyancy
   and thunderstorms are anticipated as the shortwave ejects
   northeastward over this moist and buoyant airmass. Given the
   strength of the wind fields, severe thunderstorms are likely,
   particularly across portions of the Lower MS Valley and Southeast
   where a regional outbreak of severe thunderstorms is anticipated.

   ...Lower MS Valley into the TN Valley and Southeast...
   A line of thunderstorms will likely be ongoing from the Ozark
   Plateau southwestward into East TX early Wednesday. Expectation is
   for this line of storms to quickly move eastward, outpacing a cold
   front moving southeastward into the MS Valley. Widespread clouds
   will limit diurnal heating downstream of this line of storms, but
   strong moisture advection will still result in at least modest
   buoyancy and airmass destabilization. At the same time, wind fields
   will strengthen considerably. This combination of buoyancy and very
   strong wind shear is forecast to result in a strengthening of the
   line as it moves into eastern AR and LA during the early afternoon,
   before then continuing quickly eastward across MS and AL during the
   evening and overnight.

   The kinematic fields, especially in the low-levels around 850 to 700
   mb, are forecast to be very intense. Mean wind speeds from the HREF
   show a corridor of 70 kt at 850 mb from central LA into southeast AR
   at 18Z. Deep-layer mean winds are forecast to be 65+ kt across much
   of LA, MS, and AL as the line moves through. Expectation is that
   these robust wind fields will result in an intense convective line
   capable of widespread wind damage. Embedded/QLCS tornadoes are also
   likely within this environment, including the potential for strong
   tornadoes (EF2+).  Fast storm motion could result in longer-track
   QLCS tornadoes than are typically observed.

   In addition to the strong wind gusts and embedded QLCS tornadoes,
   discrete supercells ahead of and/or south of the primary convective
   line are also possible. Any discrete storm that is able to mature
   and deepen would likely become an intense supercell capable of
   producing severe wind gusts and strong tornadoes. However, the
   forcing for ascent and fast-moving character of the shortwave (as
   well as the convective line) do not favor a discrete convective
   mode, and the current expectation is for the linear mode to
   dominate.

[yoda]

 

 

[olafminesaw]

As per usual at this range, some question as to whether discrete supercells will form ahead of the main line. Regardless, unusual to see the word "outbreak" this early in the SPC disco.

[Quincy]

At quick glance, it looks similar to last Tuesday’s event. Wind fields support more of a mixed mode/linear event, but that can yield several QLCS tornadoes, along with isolated discrete storms, especially on the southern end of the line and possibly immediately ahead of it. 

[nwohweather]

Might as well call this the new Tornado Alley at this point. I'm just not sold on a legit QLCS tornado outbreak, very atypical despite awesome parameters. I saw this a lot while living in the Great Lakes, we'd have some powerhouse low roll through with out of this world dynamics, yet at the end of the day a line is a line. We'd get a ton of wind reports, but so often the tornado threat would lack considerably.

[Iceresistance]

31 minutes ago, nwohweather said:

Might as well call this the new Tornado Alley at this point. I'm just not sold on a legit QLCS tornado outbreak, very atypical despite awesome parameters. I saw this a lot while living in the Great Lakes, we'd have some powerhouse low roll through with out of this world dynamics, yet at the end of the day a line is a line. We'd get a ton of wind reports, but so often the tornado threat would lack considerably.

The New Tornado Alley? This area is already a tornado alley. It's named Dixie Alley, & Dixie Alley has characteristics that are way different compared to Tornado Alley. 

[nwohweather]

31 minutes ago, Iceresistance said:

The New Tornado Alley? This area is already a tornado alley. It's named Dixie Alley, & Dixie Alley has characteristics that are way different compared to Tornado Alley. 

Regardless, I'm not nearly as bullish as the SPC here. Definitely looks like a major damaging wind event though, soundings show plenty of wind transferring down to the surface. We could even see a High Wind Warning as well for the area

[Iceresistance]

3 minutes ago, nwohweather said:

Regardless, I'm not nearly as bullish as the SPC here. Definitely looks like a major damaging wind event though, soundings show plenty of wind transferring down to the surface. We could even see a High Wind Warning as well for the area

Yes, wind gusts could reach Hurricane Force in the OV, & Thunderstorm gusts could reach 100 mph, that's why they've put up a very large Hatched area & Moderate risk for that, they may need to upgrade to a High Risk for destructive wind gusts between 90 & 100 mph.

[CheeselandSkies]

Yes, wind gusts could reach Hurricane Force in the OV, & Thunderstorm gusts could reach 100 mph, that's why they've put up a very large Hatched area & Moderate risk for that, they may need to upgrade to a High Risk for destructive wind gusts between 90 & 100 mph.

I think I've yet to see a high risk solely for wind actually verify, in the sense of producing an outcome so exceptional and impactful that it seemed worthy of such an unusual forecast. The only ones that would meet that criteria IMO are the May 30-31, 1998 Great Lakes derecho and the August 2020 Iowa derecho; both of which maxed out at Moderate for the derecho itself (5/31/98 got a high risk in parts of NY/PA for tornadoes later in the day, after the initial derecho had weakened).

Sent from my Pixel 4a using Tapatalk

[brooklynwx99]

this looks just as bad as last week's event

over 70kt of 0-6 bulk shear with very low LCLs, nearly saturated column, and tons of low-level SRH

the main difference with this setup is that the forcing mechanism is a dryline rather than a cold front, which often allows for more discrete activity to form. notice that the bulk shear vectors are more normal to the dryline than last event, where there was lots of deep layer shear that was nearly parallel to the cold front, which promotes QLCSs rather than discrete activity. so overall, I'm more a bit more concerned with cells ahead of the main QLCS than last week

[Iceresistance]

That wind right now is something else . . . 

[Hoosier]

4 hours ago, nwohweather said:

Might as well call this the new Tornado Alley at this point. I'm just not sold on a legit QLCS tornado outbreak, very atypical despite awesome parameters. I saw this a lot while living in the Great Lakes, we'd have some powerhouse low roll through with out of this world dynamics, yet at the end of the day a line is a line. We'd get a ton of wind reports, but so often the tornado threat would lack considerably.

I'd actually say that it's not that difficult to get a QLCS tornado "outbreak" these days, especially with the advances in radar technology that really allow these tornadic debris areas to be picked out.  The numbers can add up quickly sometimes.  I put "outbreak" in quotes because the term is a bit subjective of course.

[Quincy]

Shear vectors look close to parallel to the boundary once again, but those forecast wind fields are nothing to snooze on. I’d expect a similar outcome to the last event, but possibly a bit more widespread in terms of wind damage. Tornado potential, not much confidence beyond the QLCS threat, but it only takes one. (Remember New Orleans…)

[canderson]

Y'all be safe. Had planned to fly down tomorrow but had to push back to Thursday for work reasons. For once I am lucking out and missing the good ol' late March/early April spinning storms in DFW. 

[Iceresistance]

1 hour ago, Quincy said:

Shear vectors look close to parallel to the boundary once again, but those forecast wind fields are nothing to snooze on. I’d expect a similar outcome to the last event, but possibly a bit more widespread in terms of wind damage. Tornado potential, not much confidence beyond the QLCS threat, but it only takes one. (Remember New Orleans…)

Yes, all it takes is one

[nwohweather]

3 hours ago, Hoosier said:

I'd actually say that it's not that difficult to get a QLCS tornado "outbreak" these days, especially with the advances in radar technology that really allow these tornadic debris areas to be picked out.  The numbers can add up quickly sometimes.  I put "outbreak" in quotes because the term is a bit subjective of course.

I get you there, but when I'm saying is I'm not sold on there being a bunch of tornadoes period. Only can really see it if this event evolves into more of a "string of pearls" look than a full fledged line which is unlikely