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

NWS Huntsville Discussion
.LONG TERM...
(Thursday through Monday)
Issued at 321 PM CST Mon Feb 27 2023

Extended range models have changed very little this afternoon,
with recent guidance still indicating that the closed mid/upper-
low over the southwestern CONUS will cross the southern Rockies
and emerge into adjacent portions of the High Plains on Thursday,
before deepening into a negative-tilt trough as it lifts
northeastward into the Ozarks by 12Z Friday. Rapid development of
a surface cyclone is expected across the Red River Valley of
southeastern OK/northeastern TX as this occurs, with the low
predicted to deepen at a fairly rapid rate as it shifts
northeastward across AR early Friday morning.

If the cold front from late Wednesday night/early Thursday
morning indeed penetrates into our CWFA, it will will begin to
return northward rather quickly late Thursday morning/early
Thursday afternoon, and this could be the beginning of a fairly
significant severe weather event for our region as shear profiles
will be highly favorable for supercells and tornadoes in the
vicinity of the retreating warm front. Additional but more
scattered open warm sector convection will be possible into the
evening hours on Thursday, which may come in the form of
supercells and also present a risk for tornadoes, large hail and
damaging wind. However, forecast soundings indicate the
development of a low/mid-level inversion late in the evening,
which may allow for a temporary decrease in convective coverage
early Friday morning. To our southwest, a sharpening surface
trough extending southward from the surface low will focus the
development of a QLCS that should sweep northeastward into our
region from the Lower MS Valley in the 6-12Z timeframe Friday.
Latest model consensus has delayed the timing of this system by a
few hours, with it now predicted to enter northwest AL in the
10-12Z period Friday morning, before accelerating rapidly
northeastward through the remainder of the forecast area between
10-16Z. With mid-level winds likely to exceed 100 knots and the
low-level jet perhaps reaching the 60-70 knot range prior to the
arrival of the QLCS, a high-impact damaging wind/embedded tornado
event appears increasingly likely.

West-southwesterly winds in the wake of the surface trough/QLCS
will remain intense for much of the day Friday, before diminishing
Friday evening as a surface ridge builds southeastward. Clouds
will persist through at least the first half of the weekend, as a
secondary but much weaker mid-level trough sweeps across the
region, and this should keep low temps in the m-u 30s. Skies will
clear by Sunday, with dry weather conditions continuing through
the end of the period as highs warm back into the m-u 60s early
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small3.png
FXUS64 KJAN 280356
AFDJAN

Area Forecast Discussion
National Weather Service Jackson MS
956 PM CST Mon Feb 27 2023

Warm temperatures will continue Wednesday as a ridge brings warm
moist air into the region. As the warm front lifts north, dewpoints
will increase into the mid 60s, which should provide an unstable
environment favorable for strong thunderstorms. Despite favorable
instability, weak forcing and a strong cap should limit convective
potential and keep the threat fairly isolated. Warm moist air should
stay in place going into Thursday ahead of an approaching cold
front. Strong height falls along with a deepening upper low should
provide a strongly sheared environment. Coupled with ample moisture,
this should lead to an enhanced risk for severe weather late
Thursday and overnight with all hazards possible, before clearing
out early Friday morning. Cooler and drier conditions will persist
this weekend in the wake of the cold front with temperatures
returning to more seasonable norms. /SAS/


They're really being cautious about what they say.
 
00Z GFS sounding from south of Cedartown, GA at 15Z. Meager instability but relatively favorable wind fields. Also attached is a sounding around Montgomery, AL. Will probably continue to see model wobble with regard to parameters, but interested to see what they end up settling on as we get closer to the day of.

1677558395309.png1677558490588.png
 
Clancy said:
00Z GFS sounding from south of Cedartown, GA at 15Z. Meager instability but relatively favorable wind fields. Also attached is a sounding around Montgomery, AL. Will probably continue to see model wobble with regard to parameters, but interested to see what they end up settling on as we get closer to the day of.

View attachment 18330View attachment 18331
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Yeah, wind profiles all look good so far, but like you noted, I’m curious what the models settle on (if they do at all) instability/thermal wise. Or this could end up being a high shear/low-mod instability type event.

It’s too far out to speculate on storm mode, but at least for this far East into Dixie and if I had to make a guess. it has a more linear feel currently.
 
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CIPS has becoming even more interesting Thursday. Look at the CAPE values alone. I haven't seen a 5" on the Eff. SigTOR in a long time on these.


CWASPnam212F069.png

SVRSIGTOREFFnam212F078.png

CAPECINSBnam212F069.png
 
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JPWX said:
If SPC goes with a Day 3 Moderate Risk tomorrow, it would be the first one for MS since March 22nd, 2022. Prior to that, the last 3 for MS occurred on: April 25th, 2014, April 26th, 2014, and April 25th, 2011. It's interesting to note that all the Day 3 Moderate Risks for the state of Mississippi have occurred since 2010. @JBishopwx
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Was Mississippi not included in the Easter 2020 Day 3 moderate or maybe I’m misremembering!
 
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day3otlk_0830.gifday3prob_0830.gif
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0230 AM CST Tue Feb 28 2023

Valid 021200Z - 031200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FOR PARTS OF
NORTH/EAST TEXAS...SOUTHEAST OKLAHOMA...CENTRAL/SOUTHERN
ARKANSAS...CENTRAL/NORTHERN LOUISIANA...MISSISSIPPI...AND FAR
SOUTHWEST TENNESSEE...

...SUMMARY...
A regional severe-thunderstorm outbreak appears possible across
parts of the southern Plains into the ArkLaTex and ArkLaMiss
regions, with tornadoes, damaging wind, and hail all possible.

...Synopsis...
A deep mid/upper-level trough is forecast to become negatively
tilted as it traverses the southern Plains on Thursday. A surface
low is expected to steadily deepen somewhere near the Red River
during the day, with more rapid deepening expected Thursday night as
the cyclone moves northeastward toward the Ozarks. Seasonably rich
low-level moisture will be in place across the warm sector of the
developing cyclone through the period.

...Southern Plains into the ArkLaTex/ArkLaMiss region and parts of
the Southeast...
A regional severe thunderstorm outbreak still appears possible from
the southern Plains into the ArkLaTex/ArkLaMiss regions Thursday
into Thursday night. All severe hazards will be possible, including
the potential for widespread damaging winds and strong tornadoes,
though uncertainty remains regarding the timing and evolution of
severe thunderstorm development Thursday afternoon/evening.

Relatively steep midlevel lapse rates will support moderate buoyancy
across the moist warm sector, while deep-layer shear will steadily
increase through the day as a 80-100 kt midlevel jet approaches from
the west. The coverage and timing of convection remains somewhat
uncertain, with stronger large-scale ascent expected to remain west
of the warm sector for much of the day. Discrete supercell
development will be possible near the ArkLaTex vicinity by late
afternoon into the evening, as a low-level jet becomes increasingly
intense near/after 00Z. Any sustained supercells would pose a strong
tornado risk as low-level shear increases with time, along with the
potential for hail. More widespread development is expected along
the surging cold front across parts of north/central TX by evening.
The frontal convection will spread quickly eastward, posing a threat
of potentially widespread damaging wind and a continued tornado
threat.

Some portion of this area may eventually require a categorical
upgrade, if confidence increases regarding a corridor of
strong-tornado and/or significant-wind potential.

The eastward-surging frontal convection may tend to weaken with time
by early Friday morning across eastern MS/western AL, as the primary
mid/upper-level system begins to move northeastward away from the
region, though very strong deep-layer flow/shear will continue to
support a threat of damaging wind and line-embedded tornadoes
through the end of the period.

..Dean.. 02/28/2023
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ColdFront said:
Yeah, wind profiles all look good so far, but like you noted, I’m curious what the models settle on (if they do at all) instability/thermal wise. Or this could end up being a high shear/low-mod instability type event.

It’s too far out to speculate on storm mode, but at least for this far East into Dixie and if I had to make a guess. it has a more linear feel currently.
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Username checks out
 
Early morning AFD from FFC.

Friday, on the other hand, will be the day to watch out for. With
the current southward track of the surface low, low-level dynamics
will be more energetic than the last few systems. The Surface cold
front screams through the southeast on Thursday night and Friday,
meaning the sfc low over MO, TN, KY, and IL does not occlude until
just before the low reaches our area. Current model guidance shows
the sfc low pressure bottoming out near 980 mb. Deep moisture (PWATS
~1.5"), strong low level shear (0-1km srh ~300m2/s2, 0-3km srh ~400
m2/s2, and 3km shear of >40kts), and fairly significant CAPE for
this time of the year (Deterministic SBCAPE ~1000-1200 J/Kg) means
we would be able to support strong to severe thunderstorms early
afternoon Friday. Models, over the last few runs, have been trending
towards a less curved hodograph, particularly across the Southern
CWA, as the corridor of increased helicity has shifted eastward.
Model confidence is fairly high for this far out. GEFS mean spread
shows a 70-90% chance >250 J/kg CAPE and 50% chance >500 J/Kg CAPE.
Most of the model spread remains within timing over actual parameter
space, so expect confidence to continue to increase over the coming
days for the aforementioned CAPE values. That said, most recent
deterministic models have begun honing in on a late morning through
early afternoon cold front ETA in line with peak daytime heating.
Overall the main threats look to be damaging winds from mid level
momentum transfer and isolated tornados, hail does not look to be a
major issue at this time.

One other thing to note about the system, outside of any severe
potential, is non-thunderstorm wind potential. Gusty gradient winds
ahead of the cold front may be of concern, as the cross CWA pressure
gradient could be as high as 10-12 mb Friday afternoon.
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UK_EF4 said:
Was Mississippi not included in the Easter 2020 Day 3 moderate or maybe I’m misremembering!
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Yes it was. Sorry about that. Missed that one. I really need to go back at some point and write down all the Day 3/2 Moderate and High Risks. LOL!
 
UncleJuJu98 said:
Yeah I was thinking east Alabama and Georgia may be the second significant area other than the missippi to Texas range. I think people are sleeping on the Alabama Georgia Carolinas threat
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Modelled wind fields keep wobbling back and forth, but depending on their resolution, could definitely pose a significant risk. Either way the potential for a potent QLCS is there.
 
The one noticeable thing with east Alabama and Georgia is lack of backing winds in the low levels.
And not so great mid level lapse rates, but again we are still pretty far from the event.

*Moving forward we need to really watch trends if a more backing of the low levels occurs within the environment id say a tornado threat would go up a good bit. Some of these events takes high resolution models like the HRRR or 3km to tell but just something to watch as a secondary major severe threat with this event ; 1st being Mississippi west to Texas
 
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