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Severe WX Severe Weather Threat Jan 18-20th, 2023

UncleJuJu98

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That last picture I showed setup has potential to be a pretty major event. Still in semi voodoo land. But the GFS has had a good bit of consistent runs showing this idea. Ensembles have not come to completely same conclusion as the operational model but is close.

Screaming shear and high moisture in January yeah you got issues. Upper 60s dewpoint forecast across the deep south states with globals even forecasting 2000j of instability in those states. Luckily this is still voodoo land. But that time frame REALLY needs to be watched for a major event.
 

JPWX

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That last picture I showed setup has potential to be a pretty major event. Still in semi voodoo land. But the GFS has had a good bit of consistent runs showing this idea. Ensembles have not come to completely same conclusion as the operational model but is close.

Screaming shear and high moisture in January yeah you got issues. Upper 60s dewpoint forecast across the deep south states with globals even forecasting 2000j of instability in those states. Luckily this is still voodoo land. But that time frame REALLY needs to be watched for a major event.
Yep. Between that and next week, we're gonna be pretty busy. I figure though we'll see another big cold shot in February before we switch back around to warmth and more severe weather. Never a dull moment.
 

Timhsv

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526 PM CST Sun Jan 15 2023
Edited for emphasis:

Eyes are focused on the next system which will deepen and
occlude as it moves from the SW US into the Southern Plains on
Wednesday. A new surface low will develop and track from the
ARKLATEX into NE AR. An increasingly moist airmass will be
advected northward in advance of the system. 12z deterministic
models are a touch more unstable with perhaps a few hundred J/kg
of SBCAPE reaching to into the Mid-South. The NAM is particularly
aggressive bringing 65F dewpoints close to the area. The mid
level lapse rates are middling though. Shear profiles look quite
favorable for severe weather with veering winds with height,
looping hodographs, 0-6km bulk shear values of 60-70 kts and 0-1km
SRH values greater than 200 m2/s2. Expect showers and
thunderstorms to develop along and in advance of the cold front
as it moves across the area Wednesday afternoon into Wednesday
evening. The question will undoubtedly be the degree to which the
airmass can destabilize. If enough destabilization can occur then
this could be a dangerous event especially if storms can develop
ahead of the front in the warm sector.
 

UncleJuJu98

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South of the warm front in the green box looks to be a pretty volatile area near your triple point. Good height falls backed surface winds. Looks like it may start out discreet and grow linear.

Also the blue is supposed to be the cold front but it's further west and I already saved the picture haha. So disregard that. Screenshot_20230115-210111-439.png

Soundings are from the last two nam runs in that box. 2023011600_NAM_069_33.02,-93.12_severe_ml.png2023011518_NAM_075_32.9,-92.48_severe_ml.png
 

JPWX

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Edited for emphasis:

Eyes are focused on the next system which will deepen and
occlude as it moves from the SW US into the Southern Plains on
Wednesday. A new surface low will develop and track from the
ARKLATEX into NE AR. An increasingly moist airmass will be
advected northward in advance of the system. 12z deterministic
models are a touch more unstable with perhaps a few hundred J/kg
of SBCAPE reaching to into the Mid-South. The NAM is particularly
aggressive bringing 65F dewpoints close to the area. The mid
level lapse rates are middling though. Shear profiles look quite
favorable for severe weather with veering winds with height,
looping hodographs, 0-6km bulk shear values of 60-70 kts and 0-1km
SRH values greater than 200 m2/s2. Expect showers and
thunderstorms to develop along and in advance of the cold front
as it moves across the area Wednesday afternoon into Wednesday
evening. The question will undoubtedly be the degree to which the
airmass can destabilize. If enough destabilization can occur then
this could be a dangerous event especially if storms can develop
ahead of the front in the warm sector.
I'll be honest. It's interesting to see that type of wording from NWS Memphis as they are usually very conservative (too conservative at times) on severe weather this far out but I'm glad they're recognizing the potential.
 
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Yea it definitely seems out of character for NWS Memphis. I'm waiting to get into NAM 3km range on this before I start really analyzing it's potential and making decisions. Only thing global models have helped with lately is narrowing down which days in a generalized area have severe potential.

Damn near impossible to forecast instability in these winter setups without CAM's.
 

UncleJuJu98

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Lot of little shifting on the biggest threat area. Something that has caught my eye is the possibility of isolated supercells forming in a open warm sector in Alabama late afternoon for the day 3 event. I mean not just one or two but a few. Not a guarantee but 850 mb vertical velocity is a good Guage on supercells when compared to simulated radar. Which is hard right now to get a good view on simulated radar cause cams don't have it in the time frame just yet.

These isolated storms in Alabama won't pose a risk for major severe weather if they do form though but more of a possible spin up or downburst. Screenshot_20230116-071812-253.pngScreenshot_20230116-071759-935.pngScreenshot_20230116-071743-052.png
 

UncleJuJu98

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18z nam is more pronounced on the supercells ahead of the main stuff in n Alabama or I'll just call it storms at this point still a bit in question for using supercells.
 

Clancy

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12Z NAM seems skeptical about getting much instability into the SE on Thursday, though it does often underdo CAPE. BMX says severe possible but instability remains highly uncertain.
.LONG TERM...
(Wednesday through Sunday)
Issued at 315 AM CST MON JAN 16 2023

Wednesday through Sunday.

Warmer weather expected on Wednesday as the frontal boundary to our
north becomes more established as a warm front with the developing
low pressure system to our west. This trough and associated low
pressure system is expect to push a cold front eastward through
Central AL late Wednesday night into Thursday. With the proximity of
the surface low and the upper level dynamics of this system, there
should be enough shear to support a more organized development of
strong storms as the QLCS moves through our area. The biggest
question is still instability to determine severity.
With lack of
significant height falls, we don`t really see steep lapse rates, and
therefore, the instability remains limited. This will likely evolve
into a low CAPE/high shear QLCS event with an chance for isolated
damaging winds and maybe a few brief embedded tornadoes if anything
can really get established. I`ll include a mention for strong to
severe storms in the forecast for overnight Wednesday night into
Thursday, but I do want to emphasize that it`s highly conditional on
the instability. If we don`t see the destabilization, we may only
see a line of sub-severe thunderstorms move through.
 

UncleJuJu98

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I am a liiiiitle surprised SPC did not highlight D4 today.
I'm not, this is a more Mississippi Delta threat once it moves past there values start to become more unfavorable. The stuff I was talking abour for Alabama would just be a very good spectacle it would make good photography and views with these small supercells popping up in a not so much cloudy skies.
 

UncleJuJu98

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Look at the day 7-8 timeframe period that I thought could be a major event for the southeast really remarkable values on a global which I've always thought whenever you see very high values on globals you have potential for a major event. Supercell composite is high, but I tend to look at ehi more in terms of atmosphere capability. One issue I see is if we don't get around that threshold of 2000j+ of instability these storms will probably end up being shredded with how much speed shear there is. Unfortunately... I don't see it being a issue at this point. I'm telling you this could be the big one. Been playing around with all these barreling lows until one rolls it's dice right and you got a big time event on your hands. Still lots of time to change. But the GFS Operational has been incredibly consistent. Which is another belief of mine these major events typically forecast and hold together further out in forecast than your mid major events.

Synoptically though in conclusion.. this one has some potential. If models ain't crapping on everybody lol
Last 6 GFS Operational runs
Screenshot_20230116-084750-429.pngScreenshot_20230116-084639-894.png2023011606_GFS_231_32.89,-88.58_severe_ml.png
99113421-78e0-4e40-8b40-00ddbf22ac72.gifd4754527-73e0-44ab-bf7d-ea41cfd96ef2.gif
 
Last edited:

KevinH

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Look at the day 7-8 timeframe period that I thought could be a major event for the southeast really remarkable values on a global which I've always thought whenever you see very high values on globals you have potential for a major event. Supercell composite is high, but I tend to look at ehi more in terms of atmosphere capability. One issue I see is if we don't get around that threshold of 2000j+ of instability these storms will probably end up being shredded with how much speed shear there is. Unfortunately... I don't see it being a issue at this point. I'm telling you this could be the big one. Been playing around with all these barreling lows until one rolls it's dice right and you got a big time event on your hands. Still lots of time to change. But the GFS Operational has been incredibly consistent. Which is another belief of mine these major events typically forecast and hold together further out in forecast than your mid major events.

Synoptically though in conclusion.. this one has some potential. If models ain't crapping on everybody lol
Last 6 GFS Operational runs
View attachment 16921View attachment 16922View attachment 16923
View attachment 16924View attachment 16925
Always. The same. Areas. SMH

Appreciate your posts. Keep them coming.
 

Taylor Campbell

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Look at the day 7-8 timeframe period that I thought could be a major event for the southeast really remarkable values on a global which I've always thought whenever you see very high values on globals you have potential for a major event. Supercell composite is high, but I tend to look at ehi more in terms of atmosphere capability. One issue I see is if we don't get around that threshold of 2000j+ of instability these storms will probably end up being shredded with how much speed shear there is. Unfortunately... I don't see it being a issue at this point. I'm telling you this could be the big one. Been playing around with all these barreling lows until one rolls it's dice right and you got a big time event on your hands. Still lots of time to change. But the GFS Operational has been incredibly consistent. Which is another belief of mine these major events typically forecast and hold together further out in forecast than your mid major events.

Synoptically though in conclusion.. this one

Can you please put this information in the correct thread (Severe Weather 2023). Thank you.
 

JPWX

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It's worth noting that the 12z NAM CWASP is more aggressive on Wednesday. I don't know but given how last Thursday went, we could be dealing with another low end event that turns into something significant. Slight Risk probably gets expanded eastward and upgrade to Enhanced for portions of the MS Delta into Eastern MS.
Screenshot 2023-01-16 113839.png
 

Clancy

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It's worth noting that the 12z NAM CWASP is more aggressive on Wednesday. I don't know but given how last Thursday went, we could be dealing with another low end event that turns into something significant. Slight Risk probably gets expanded eastward and upgrade to Enhanced for portions of the MS Delta into Eastern MS.
SREF's STI has values of 30 over far E TX and NW LA at 21Z on Wednesday. Not particularly high but distribution is approximately the same, so that area may end up being the focus point for tornadic development.
1673891473511.png
 

UncleJuJu98

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It's worth noting that the 12z NAM CWASP is more aggressive on Wednesday. I don't know but given how last Thursday went, we could be dealing with another low end event that turns into something significant. Slight Risk probably gets expanded eastward and upgrade to Enhanced for portions of the MS Delta into Eastern MS.
View attachment 16926
That model actually did very good from what I remember.
 
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Based on first run of NAM 3km it looks like there could be some messy convection that initiates in AR/LA before 12pm and then develops into a line of semi discrete storms right at dark. The instability plummets quickly after sunset. The time window to catch a tornado seems small but I think best potential will be near the River at 5pm. A lot may change but right now I have my target as Lake Village, AR.

At the moment I don't see Wednesday exceeding an Enhanced risk.... especially since the population is so low in the Delta region. SPC won't get burned if they are wrong or if the system overperforms.
 
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