November 29th-30th, 2022 | Severe Weather | Lengthy Dixie Alley Tornado Outbreak on the 29th

[Iceresistance]

Surprise!

[Neoncyclone]

Here's the 12z GFS, still really far out. Hopefully we don't get more instability than this because there's a pretty wide swath of favorable directional shear.

Edited November 23, 2022 by Neoncyclone

[Iceresistance]

It has moved further south

[ClicheVortex2014]

I’m gonna be without internet until Monday at my apartment so I can’t share images but I’ve been watching the runs at work. Looking pretty nasty but we’ll see what the storm mode will be.

Edited November 25, 2022 by ClicheVortex2014

[ClicheVortex2014]

Day 5 enhanced. Can’t say I’m too surprised.

   Day 4-8 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0231 AM CST Fri Nov 25 2022

   Valid 281200Z - 031200Z

   ...DISCUSSION...
   Medium-range guidance continues to show a potent large-scale trough
   digging south across the western U.S. on Day 4/Mon, and ejecting
   eastward across the Plains toward the MS Valley on Day 5/Tue. As
   this occurs, strong southerly low-level flow will develop across
   eastern parts of southern Plains to the Lower MS Valley in response
   to strengthening cyclogenesis over the central/southern Plains. This
   will transport unseasonably rich Gulf moisture northward across
   eastern OK/TX into the Lower MS Valley beneath intense vertical
   shear. 

   Details continue to shift with regards to the north and east extent
   of quality boundary-layer moisture return, and in how far east a
   surface cold front will surge by Day 6/Wed morning. However,
   agreement between deterministic, ensemble and machine-learning
   guidance supports greater than average confidence that a corridor of
   severe potential will exist from eastern TX into the Lower MS Valley
   on Day 5/Tue. Furthermore, a corridor of enhanced severe potential
   appears likely within the broader risk area across the ArkLaMiss
   vicinity. While confidence is high that severe potential will exist
   on Day 5/Tue, the area delineated may continue to shift some in the
   coming days, depending on trends in system amplitude and within
   forecast guidance.

   Forecast guidance varies quite a bit moving into Day 6/Wed regarding
   the extent of the warm sector across the central Gulf coast
   vicinity. Some severe potential may continue into parts of
   MS/AL/GA/FL, but confidence remains low regarding intensity and
   coverage, precluding unconditional severe probabilities at this
   time. 

   By Day 7/Thu, strong surface high pressure across the eastern U.S.
   will result in a dearth of boundary-layer moisture, and severe
   potential will be low. Medium range guidance then depicts another
   large-scale upper trough over the western U.S. shifting east toward
   the Rockies/Plains, supporting another surge of Gulf return flow
   across the south-central U.S. Severe thunderstorm potential is
   uncertain on Day 8/Fri, but could increase late in the period into
   next weekend.

 

[Ingyball]

Right now I'm thinking we're going to be dealing with a deeper trough that digs further south than models are showing at the moment. That might favor a more linear event due to widespread forcing, but we'll have to see. 

[ClicheVortex2014]

 

[ClicheVortex2014]

Still looking nasty on the models. We’ll see what happens when we get sampling. My big question remains storm mode, because there’s no doubt that everything else is there for now.

Of course we’ll see a frontal squall but conditions along the front aren’t nearly as dangerous as the warm sector. Gonna need some kind of forcing to get cells kicked off ahead of the cold front. Hour 84 NAM will show us a bit in that regard but that’s gonna need to be taken with a grain of salt 

[Neoncyclone]

A bit surprised there are no areas highlighted tomorrow for NC, plenty of SFC cape and favorable shear, only thing I can think of is lapse rates are pretty weak may be difficult to sustain deep convection.

 

Edited November 26, 2022 by Neoncyclone

[ClicheVortex2014]

Good catch here. Wow.
 

 

Edited November 26, 2022 by ClicheVortex2014

[ClicheVortex2014]

 

[ClicheVortex2014]

 

[StormfanaticInd]

I'm starting to get worried about this one. 

Edited November 26, 2022 by StormfanaticInd

[Neoncyclone]

5 hours ago, ClicheVortex2014 said:

 

Yeah that's a fantastic comparison, I noted in the first few posts about the wind shear being favorable in a large swath. That's the type of steady state environment that can make a tornado outbreak memorable and sometimes historic.

Long range NAM is pretty scary, but keep in mind it is the long range NAM.

Hopefully being further south we see a super messy storm mode like what happens sometimes especially in LA.

Edited November 27, 2022 by Neoncyclone

[ClicheVortex2014]

As far as forcing… NAM continues to show weak warm sector activity. But there have been hints of subtle warm sector forcing such as surface wind convergence that raises the possibility for discrete warm sector storms which would obviously be supercellular.

Either way, I think the pretty strong secondary warm front could force some convection as well.

Gfs has it a bit. (You’re looking at where surface winds converge)

NAM not as much yet.

 

The CAMs and HRRR should be a good judge as to whether or not there’ll be surface wind convergence

Heres gfs and NAM respectively. Nothing sticks out other than the fact that the warm sector isn’t clear. Might be trying to develop warm sector storms, might be failing. Either way, seems there’s good reason to watch the open warm sector

[ClicheVortex2014]

SREF has 45 sigtor contour. Keep in mind it requires convective precip, otherwise the value goes to 0

[ClicheVortex2014]

Insight from the SPC forecaster

 

[StormfanaticInd]

Oz nam would be a major outbreak 🌪️

[CentralLA_Wx]

SPC extended the risk further north. Memphis area now in the enhanced risk. Also the enhanced shifted a bit to my north. 

 

Edited November 27, 2022 by CentralLA_Wx

[snowlover2]

2 hours ago, CentralLA_Wx said:

SPC extended the risk further north. Memphis area now in the enhanced risk. Also the enhanced shifted a bit to my north. 

 

Here is the disco for the day 3 which has from pretty strong wording including strong tornadoes and tornado outbreak. Have to wonder if they add a moderate risk area at some point.

Quote

 Day 3 Convective Outlook CORR 1
   NWS Storm Prediction Center Norman OK
   0241 AM CST Sun Nov 27 2022

   Valid 291200Z - 301200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   THE LOWER TO MID MISSISSIPPI VALLEY...

   CORRECTED FOR WORDING

   ...SUMMARY...
   Severe thunderstorms with wind damage and tornadoes, along with some
   hail, will be possible from the Sabine River Valley and lower
   Mississippi Valley north-northeastward into the mid Mississippi
   Valley on Tuesday. A significant severe-weather event will be likely
   across parts of the region.

   ...Lower to Mid Mississippi Valley/Sabine River Valley/Eastern
   Ozarks...
   A highly progressive upper-level trough will move quickly into the
   southern and central Rockies on Tuesday. Ahead of the system, a
   broad 40 to 60 knot low-level jet will transport low-level moisture
   northward across east Texas and the lower Mississippi Valley, where
   surface dewpoints should reach the lower to mid 60s by midday. In
   response to moisture advection and surface heating, moderate
   instability is forecast to develop by early afternoon across much of
   east Texas and Louisiana. Isolated to scattered convective
   initiation will be possible in the early afternoon from near the
   instability axis eastward across the lower Mississippi Valley. A
   severe threat will be possible with this activity.

   Moisture will continue to advect northward into the eastern Ozarks
   and mid Mississippi Valley during the late afternoon and early
   evening. This will set up a broad corridor of moderate instability
   across much of the lower to mid Mississippi Valley. As the
   upper-level trough approaches from the west, the low-level jet is
   expected to strengthen into the 50 to 70 knot range by early
   evening. This combined with increasing deep-layer shear, associated
   with an approaching southern Plains mid-level jet, will make
   conditions very favorable for severe thunderstorms across the lower
   to mid Mississippi Valley. NAM forecast soundings along the axis of
   strongest instability, from northeast Louisiana into eastern
   Arkansas, by 03Z Wednesday have MLCAPE in the 1500 to 2000 J/kg
   range, with 0-6 km shear in the 60 to 70 knot range. This combined
   with a long and looped hodographs, with 0-3 km storm-relative
   helicities in the 400 to 500 m2/s2 range, will be favorable for
   supercells and tornadoes. A few strong tornadoes will be possible
   with the more dominant supercells that remain discrete. The most
   favorable area for strong tornadoes may develop along the western
   edge of the low-level jet, as is forecast by the ECMWF, from eastern
   Arkansas into northwest Mississippi and western Tennessee. A tornado
   outbreak will be possible across parts of the lower to mid
   Mississippi Valley, if the current forecast parameters, such as
   instability, deep-layer shear and low-level shear remain at current
   forecast levels.

   In addition to the tornado threat, the potential for wind damage
   will likely increase during the evening as storm coverage and the
   chance for cell interactions increase. Mid-level lapse rates are
   also expected to be steep, which should support a hail threat with
   the more intense cells. The extent of moisture return will determine
   how far north-northeast the severe threat develops. At this time, it
   appears that at least some severe threat will be possible during the
   evening and overnight period as far north as southern Illinois and
   southwest Indiana. A categorical upgrade will be possible in later
   outlooks.

   ..Broyles.. 11/27/2022

 

 

[ElectricStorm]

Really good chance this goes moderate at some point imo. Probably on the Day 2

[ClicheVortex2014]

CAMs are getting into range. Of course FV3 goes nuts but 3km NAM also shows some warm sector convection 

[ClicheVortex2014]

Starting to see some warm sector convection on 12km NAM.

Insane sounding regardless of the time of year. But this is unbelievable for late November. 3000 cape, very well defined EML, low 70 dew points. This is in eastern texas.

[ClicheVortex2014]

Fwiw, 18z HRRR shows plenty of warm sector convection at 18z Tuesday

[StormfanaticInd]

3 hours ago, ClicheVortex2014 said:

Starting to see some warm sector convection on 12km NAM.

Insane sounding regardless of the time of year. But this is unbelievable for late November. 3000 cape, very well defined EML, low 70 dew points. This is in eastern texas.

3000 cape in late November is crazy! Let's hope this does not verify