Severe WX Severe Weather Threat - February 15-16, 2023

[Austin Dawg]

Jackson, MS Discussion tonight

Area Forecast Discussion
National Weather Service Jackson MS
908 PM CST Mon Feb 13 2023

A second wave should pass in the Wednesday-Thursday time frame and
associated low pressure system could provide a potentially favorable
environment for severe weather. While best forcing will remain
northwest, a favorable robust warm sector with mid 60s dew points,
deep shear, and strong helicity values could potentially aid in
Wednesday afternoon to evening supercell development. Current
guidance continues to show favorable probabilities for all hazards,
including damaging winds, large hail and tornadoes. This looks to be
a long duration event over the late Wednesday afternoon-Thursday
time frame. The first concern will be with the afternoon to evening
convection that could develop along the northward lifting warm
front/moisture plume. While not much convective initiation is
indicated in current guidance, potential is there that any activity
could be very robust and severe. This activity/potential will remain
as the deep trough/height falls and cold front move in, leading to
additional convective activity, with all modes, before moving into
ESE MS by Thursday morning and persisting through the afternoon.
Favorable SREF sig tor ingredients and CWASP have been hitting a
little harder on the Wednesday afternoon activity in MS River
corridor to northwest Delta and less on the overnight to Thursday
activity. Will continue to message the HWO/graphics the same, other
than to hit multiple rounds, first for the northwest late Wednesday
afternoon through early Thursday and later round for early Thursday
through the afternoon. Additionally, a tight pressure gradient
should remain in place through Wednesday night, keeping the
potential for strong wind gusts. Have highlighted a Limited risk for
strong winds for much of the area Wednesday night. With fast
progressive nature of the system, rain totals have lowered in global
consensus models. If any more robust warm front activity can get
going, that could heighten flooding potential. Holding off mention
for now.

 

[JBishopwx]

.THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM PARTS OF
TEXAS AND OKLAHOMA EASTWARD INTO THE LOWER MISSISSIPPI VALLEY AND
LOWER OHIO VALLEY...

...SUMMARY...
Widely scattered severe thunderstorms are possible over parts of
Texas and Oklahoma beginning Wednesday during the late afternoon and
evening. A severe threat will also develop east and include the
lower Mississippi Valley Wednesday evening and into the overnight,
while also developing into parts of the lower Ohio Valley.

...Synopsis...
A somewhat complex, multi-modal severe episode is forecast from
parts of OK/TX eastward through parts of the Mid South and into the
lower MS/OH Valleys.

A potent mid-level low and associated trough over the Desert
Southwest will move east into the central US while the trough
acquires a positive tilt. A trailing surface front from a Great
Lakes cyclone will extend southwestward through the Ozarks and into
the southern High Plains early Wednesday morning. A surface low is
forecast to develop eastward along the boundary and reach central OK
by early evening, and subsequently into southeast MO by daybreak
Thursday. An arctic front will sweep southeast across OK and reach
the TX coastal plain by the end of the period.

...TX/OK into the lower MS/OH Valleys...
Southerly low-level flow will advect increasing moisture north into
parts of TX/OK and the lower MS Valley during the day. The
ECMWF/RAP/NAM are in general agreement in showing a surge of lower
60s deg F dewpoints into the Red River Valley by early Wednesday
evening. Model guidance is suggesting isolated to scattered
thunderstorms will develop by the early evening along the dryline
near the Red River. Moderate buoyancy (1000-1500 J/kg MLCAPE)
forecast over north TX and long hodographs (effective shear 65-70
kt) will favor supercells. Large to very large hail is possible
with the more intense storms and potentially an isolated tornado
risk. Some of this activity will likely move downstream into
northeast TX/eastern OK and perhaps persist into portions of AR
during the overnight, with the severe hazards largely governed by
the convective mode.

Farther east, a persistent low-level WAA corridor acting to advect
moisture north will destabilize the airmass over the ArkLaMiss. By
early evening, models indicate isolated to scattered thunderstorms
developing on the nose of a strengthening south-southwesterly LLJ
centered overhead. The LLJ is forecast to further intensify
Wednesday night as it shifts northward into the lower TN/OH Valleys
by early Thursday morning. Enlarged and elongated hodographs imply
some of this evening/overnight activity to evolve into a cluster of
supercells. A supercell-tornado risk may develop along with other
severe hazards possible.

Eventual storm mergers and additional storm development will favor a
severe risk developing into the lower OH Valley late overnight, as
moisture advects north through the MS Valley as the exit region of
the LLJ focuses over the region. Farther south into parts of east
TX/western LA, strengthening large-scale ascent will likely promote
scattered thunderstorms. A risk for damaging gusts and perhaps a
tornado may accompany this activity during the overnight.

 

[JBishopwx]

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE CENTRAL
GULF COAST NORTHWARD INTO THE OHIO VALLEY AND LAKE ERIE VICINITY...

...SUMMARY...
Widely scattered severe thunderstorms are possible from the central
Gulf Coast states northward into the Ohio Valley and Lake Erie
vicinity on Thursday and Thursday evening. Severe gusts capable of
wind damage and tornadoes are the primary severe hazards.

...Synopsis...
Another severe episode, and potentially becoming bi-modal in spatial
coverage, is forecast on Thursday through Thursday evening. A
large-scale, positively tilted mid-level trough will gradually move
from the central Great Plains into the Desert Southwest to the Great
Lakes and Ozark Plateau. A belt of intense 500-mb flow will move
northeast to the east of the eastward-progressing trough axis. In
the low levels, a surface low will migrate northeast from southeast
MO to the Lower Great Lakes Thursday night. A cold front will sweep
southeastward across the lower MS Valley and OH Valley before
reaching the Appalachians.

Considerable shower/thunderstorm activity is expected to be ongoing
Thursday morning from the OH Valley southward into the lower MS
Valley. Some of these storms, likely already grown upscale into
lines and bands of storms, will probably pose some risk for strong,
damaging gusts and perhaps a localized tornado risk. It is
uncertain whether these initial storms continue east and some of
them re-intensify during the day, or additional storms develop in
their wake where some destabilization can occur. Regardless, it
seems the warm sector with 100-500 J/kg MLCAPE will overspread much
of the OH Valley. Low-topped bands of storms within strong
deep-layer southwesterly flow will favor at least some threat for
damaging gusts on the northern portion of the warm sector. Some of
these storms or low-topped convective bands may pose a wind hazard
well into the evening near/southeast of the surface low track.

Farther south, multiple storm modes (i.e., linear convection and
supercells) may evolve and maximize their threat during peak heating
across parts of AL/MS. Richer low-level moisture and greater
buoyancy may result in the threat for a few tornadoes and widely
scattered damaging gusts. Several clusters of storms will likely
spread from west to east across the central Gulf Coast states before
this activity gradually weakens, and the severe risk wanes by the
mid evening along the coastal plain.

 

[KevinH]

I hate to be THAT guy, but this seems to be a little “outbreak-ish” to me.

 

[UncleJuJu98]

no offense, but is this your job?

that was the most backhanded comment lol, gotta put no offense in there even though the question is totally offensive lol [/QUOTE]

 

[UncleJuJu98]

Looks like 06z is ont track for some nasty updrafts storms. Across Arkansas and missippi wensday and wensday night. Pretty good swaths through midnight wensday. Doesn't correlate to tornadoes, but does show healthy storms.

High STP values along and near the Arkansas storms through the evening and night reaching values of 7-8

 

[CheeselandSkies]

Seems the expert consensus for the last 36 hours or so has been that overnight Wednesday-Thursday is the timeframe of greatest interest for a significant tornado threat. 06Z HRRR would seem to concur with that.

 

[UncleJuJu98]

Seems the expert consensus for the last 36 hours or so has been that overnight Wednesday-Thursday is the timeframe of greatest interest for a significant tornado threat. 06Z HRRR would seem to concur with that.

Unfortunately those areas might see a round two or at least Mississippi, cold front is still all the way in central Texas by midnight on wensday lol, leaves a lot of time for Alabama and Mississippi to destabilize wether the shear is good enough or not in thos areas Thursday afternoon

 

[tennessee storm chaser]

MEG nws Memphis calling for super cells crossing ms River tonight amongst the cluster of storms . Tornadoes possible tonight late

 

[tennessee storm chaser]

MEG nws Memphis calling for super cells crossing ms River tonight amongst the cluster of storms . Tornadoes possible tonight late. Edit. Tomorrow night. Sorry

 

[The Nino]

that was the most backhanded comment lol, gotta put no offense in there even though the question is totally offensive lol

[/QUOTE]
it was a totally genuine question. You are very dedicated to this stuff, more power to ya bro

 

[UK_EF4]

12z HRRR is basically the summary of my concerns over the last few days… discrete supercells initiating across AR and nw MS via a subtle shortwave (or it may have been confluence band I haven’t checked properly) in an environment which has been trending upwards as cams come into range. I wouldn’t be surprised to see 10 or 15%# risks in future outlooks, especially as moisture is likely trend further up.

 

[UncleJuJu98]

Gobbly gook. The FV3 is supercell heaven at midnight wensday; thankfully I doubt it'll be that bad, usually fv3 has a hot bias.

 

[UK_EF4]

Gobbly gook. The FV3 is supercell heaven at midnight wensday; thankfully I doubt it'll be that bad, usually fv3 has a hot bias. View attachment 17815

For once I don't think it's actually too far off.


Most/all other CAMS have a similar precipitations signal for discrete convection in a similar area... and we know a line of supercells like the FV3 depicts totally makes sense given most models agree on a subtle shortwave trough moving through.

I am beginning to get increasingly concerned about Wednesday and slightly worried that some people (not so much here but on twitter) are viewing it as your more typical February threat just because there was a downgrade, when we could have discrete supercells in an environment of roughly 2-4 STP (not that that is a good forecasting tool but just illustrates the environment). I do think SPC will probably go 10%# at some point either today or tomorrow in a corridor of N LA, E AR and NW MS - though we will say and I could very well be completely off

 

[UncleJuJu98]

For once I don't think it's actually too far off.

View attachment 17816
Most/all other CAMS have a similar precipitations signal for discrete convection in a similar area... and we know a line of supercells like the FV3 depicts totally makes sense given most models agree on a subtle shortwave trough moving through.

I am beginning to get increasingly concerned about Wednesday and slightly worried that some people (not so much here but on twitter) are viewing it as your more typical February threat just because there was a downgrade, when we could have discrete supercells in an environment of roughly 2-4 STP (not that that is a good forecasting tool but just illustrates the environment). I do think SPC will probably go 10%# at some point either today or tomorrow in a corridor of N LA, E AR and NW MS - though we will say and I could very well be completely off

Good post, may be a significant nocturnal event for the Mississippi delta region and a bit west of that. I could honestly see a potential 30% depending on how well some of the factors line up. Seems like each new close range run the the surface pressure is closer to the deep south.

We very well could have a memorable tornado event in the deep south too early to start forecasting it but some of the ingredients are there.

Here's the latest MMFS run simulated radar.

 

[UncleJuJu98]

For once I don't think it's actually too far off.

View attachment 17816
Most/all other CAMS have a similar precipitations signal for discrete convection in a similar area... and we know a line of supercells like the FV3 depicts totally makes sense given most models agree on a subtle shortwave trough moving through.

I am beginning to get increasingly concerned about Wednesday and slightly worried that some people (not so much here but on twitter) are viewing it as your more typical February threat just because there was a downgrade, when we could have discrete supercells in an environment of roughly 2-4 STP (not that that is a good forecasting tool but just illustrates the environment). I do think SPC will probably go 10%# at some point either today or tomorrow in a corridor of N LA, E AR and NW MS - though we will say and I could very well be completely off

Also I think the environment STP wise will be WAY higher. Closer to your 6-8 range. Especially if what the WRF and HRRR are forecasting of 2000j or so all the way into about south Arkansas and northwest Mississippi. EHI Is a good product to use if there's contamination but it doesn't look like there is from the runs I saw.

 

[The Nino]

so where are we thinking the bullseye for this event is? I have been casually monitoring this thread and the models and feel like they have waffled a bit on this threat. It was definitely looking concerning last week

 

[UncleJuJu98]

so where are we thinking the bullseye for this event is? I have been casually monitoring this thread and the models and feel like they have waffled a bit on this threat. It was definitely looking concerning last week

Hate to say it, but I feel like it's impossible to say lol. Because a lot of convection will probably start blooming from mesoscale features I'm afraid. Not from a a well defined cold front for some of the locations. I think a good chunk of the area from Texas to about Georgia will have a decent chance for some bad weather.

*Personally if I had to choose ground zero though. I'd pick central/north Mississippi and the northwest of Alabama overnight into midday.*

 

[UK_EF4]

Also I think the environment STP wise will be WAY higher. Closer to your 6-8 range. Especially if what the WRF and HRRR are forecasting of 2000j or so all the way into about south Arkansas and northwest Mississippi. EHI Is a good product to use if there's contamination but it doesn't look like there is from the runs I saw.

This is not supposed to be addressed to you btw (just a sudden thought sparked in my head which is related), but I feel like a lot of people often really overestimate how much STP you 'need' - 2 are the values where strong tornadoes are considered possible, and there have been many cases of violent tornadoes in STPs of 3-5: for example the Quad-State tornado produced what most consider one of the most violent tornadoes of the decade or even century while in a region of STP 3/4.

I think this stems from the fact that every so often we get an event coming round where the parameters are extremely maxed out (e.g April 12th 2020 or March 25th 2021) and people think that is what we need for strong tornadoes, when actually it's not completely necessary - what is more necessary is a discrete sustained supercell! Or the fact we see a lot of maxed out STP model charts which often dont come to fruition, though all of this just goes to show why composite paramaters have their weaknessess

And taking a box sounding from HRRR tomorrow (NW MS) you can see the values are in that range... and so finally getting back to your point, yes maybe if we get a continued upward trend instability values of 5-6 are possible, though personally would consider 8 a bit of a stretch. But yeah, do think tomorrow could end up with a pretty volatile environment, whether that comes to fruition or not.

 

[The Nino]

This is not supposed to be addressed to you btw (just a sudden thought sparked in my head which is related), but I feel like a lot of people often really overestimate how much STP you 'need' - 2 are the values where strong tornadoes are considered possible, and there have been many cases of violent tornadoes in STPs of 3-5: for example the Quad-State tornado produced what most consider one of the most violent tornadoes of the decade or even century while in a region of STP 3/4.

I think this stems from the fact that every so often we get an event coming round where the parameters are extremely maxed out (e.g April 12th 2020 or March 25th 2021) and people think that is what we need for strong tornadoes, when actually it's not completely necessary - what is more necessary is a discrete sustained supercell! Or the fact we see a lot of maxed out STP model charts which often dont come to fruition, though all of this just goes to show why composite paramaters have their weaknessess

And taking a box sounding from HRRR tomorrow (NW MS) you can see the values are in that range... and so finally getting back to your point, yes maybe if we get a continued upward trend instability values of 5-6 are possible, though personally would consider 8 a bit of a stretch. But yeah, do think tomorrow could end up with a pretty volatile environment, whether that comes to fruition or not.

I know for me personally, following April 27 2011 event forever skewed my perception of STP. Prob and hopefully will never see those values again in such a large area