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11/29/22 MDT Outlook Issued -- Regional outbreak possible.


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The rare November 30% region has popped up again for day 5. Feels like given the rather concerning wording from NWS that a potentially mdt-high end weather event seems possible for Monday (edit: TUESDAY).

At this points seems like it's worthy of it's own thread. Will we see another late fall svr wx event? It bears keeping a very close eye on the incoming d3 prediction, especially if you're in the 30% ENH risk this far out.



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   ACUS48 KWNS 250831
   SPC AC 250831

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

   Valid 281200Z - 031200Z

   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

   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

   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.

   ..Leitman.. 11/25/2022
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Looking at the LSX afternoon disco, they seem to think there could be some potential into SE MO and Southern IL. Very interested to see how the outlooks progress tomorrow and into Tuesday. A few shades of Dec 10 of last year. Hopefully nothing like the destructive results of that outbreak.

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The Day-3 enhanced outlook is very concerning for this region. Maybe this could go into a moderate risk outlook for tornadoes and wind when we get to the event. The severe weather parameters such as the STP will greatly increase from 21z to 06z. The NAM and GFS have much different values for the 850mb wind in the region in this time frame, as the NAM has up to 60kt in E Arkansas but the GFS is lower. Note the GFS has values of STP of 1.0-2.0 in the Louisiana area. That's still impressive, but not as impressive as this chart.




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Unfortunately this seems to be a situation of increasing importance/alarm for the deep south.




Valid 291200Z - 301200Z



   Severe thunderstorms with tornadoes and wind damage, along with some
   hail, will be likely on Tuesday afternoon and evening, extending
   into the overnight period across parts of the lower to mid
   Mississippi Valley. Significant and/or long-track tornadoes will be

   ...Regional Tornado Outbreak Possible Tuesday Afternoon and Evening
   Across Parts of the Lower to Mid Mississippi Valley...

   ...Lower to Mid Mississippi Valley/Sabine River Valley/Western Ohio
   and Tennessee Valleys...
   A progressive upper-level trough will move quickly eastward across
   the Rockies Tuesday and into the Great Plains. Ahead of the system,
   a moist airmass, with surface dewpoints in the lower to mid 60s F,
   will advect northward across the lower and mid Mississippi Valleys.
   Thunderstorm development will be likely during the day on the
   eastern edge of the most airmass, from the central Gulf Coast states
   northward into the western Ohio Valley. While elevated, an isolated
   severe threat will be possible with some of this convection. Further
   to the southwest, an axis of moderate instability is forecast to
   develop by mid to late afternoon from northwest Louisiana
   northeastward into far eastern Arkansas. This airmass should
   continue to destabilize during the evening, as rich low-level
   moisture streams north-northeastward, with MLCAPE reaching the 1500
   to 2000 J/kg range by 03Z Wednesday across parts of northern
   Louisiana, southeast Arkansas and northwest Mississippi.
   Surface-based convective initiation appears likely to occur during
   the late afternoon and early evening in northern Louisiana, with
   these storms tracking northeastward across far southeast Arkansas
   and into northwest Mississippi. 

   Throughout the day on Tuesday, deep-layer shear will steadily
   increase across the region as a 70 to 90 knot mid-level jet
   translates quickly eastward across the south-central U.S. This jet
   is forecast to move through the base of the trough at around 55
   knots, which will help sustain a 40 to 60 knot low-level jet ahead
   of the system. NAM forecast soundings along the most favorable
   corridor from far northeast of Monroe, Louisiana to near Memphis,
   Tennessee at 03Z Wednesday, have MLCAPE in the 1500 to 2000 J/kg
   range, with 0-6 km shear near 70 knots, and 0-3 km storm-relative
   helicities around 400 m2/s2. Hodographs are forecast to be long and
   curved, suggesting the environment will be favorable for tornadic
   supercells. A long-track and/or significant tornadoes will be
   possible, with the most favorable corridor located from far
   northeast Louisiana northeastward across northwest Mississippi. An
   earlier and further southwest convective initiation would be most
   favorable for a tornado outbreak, which would give the storms more
   time to move northeastward through the most unstable air. Supercells
   will also have potential for wind damage and isolated large hail.
   During the mid to late evening, a strengthening low-level jet should
   help maintain the severe threat across the region. A threat for
   tornadoes, wind-damage and hail will be possible with supercells and
   with organized bowing line segments from mid evening into the early
   overnight period.

   Further northeast into north-central Tennessee, western Kentucky and
   far southern Illinois, moisture advection during the early to mid
   evening, will likely increase dewpoints into the lower 60s F. As a
   cold front approaches from the west, scattered thunderstorms are
   expected to develop across the moist sector. Although instability is
   forecast to be weak ahead of the front, large-scale ascent should be
   very focused due to the approaching trough. This combined with
   strong deep-layer shear should support a severe threat, with wind
   damage and a few tornadoes possible.

   ..Broyles.. 11/28/2022

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The SE forum is mostly comprised of people in the Carolinas. They'll closely follow a 384hr model predicting a trace of snow in the Piedmont but they have 0 interest in severe. Kind of the same with TN Valley. Just how they are. 

I’ve noticed this too. To be fair my western Ohio self has seen too many tornadoes and derechos to not love severe weather.

What concerns me with this event is you have a strong deepening low giving us a jet that is going to be absolutely howling. As long as lapse rates don’t get too bad we could see some serious tornadoes tomorrow
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Area Forecast Discussion
National Weather Service Memphis TN
553 PM CST Mon Nov 28 2022

...New AVIATION...

(This evening through next Sunday)
Issued at 336 PM CST Mon Nov 28 2022

A potential high-end severe weather event remains on track to
impact the Midsouth on Tuesday and Tuesday night. Tornadoes, a
few strong and long-lived, will be possible.

Low level moisture and instability will surge north through the
lower MS River valley Tuesday morning, in advance of a deepening
upper level longwave trof over the Great Plains. Initial round of
late morning/early afternoon storms will likely root in an elevated
layer, associated with a 925mb warm front surging north from the
Arklamiss. These storms will likely present a marginal severe
threat in the early afternoon, with midlevel lapse rates of 6.5
C/km accompanying MUCAPE below 300 J/KG.

The potential for storms to become rooted in a near-surface layer
will increase mid to late afternoon, aided by modest surface
heating and dewpoints rapidly warming into the mid/upper 60s.
During this period, convection-allowing model (CAM) consensus
depicts 850mb wind increasing from 40 to 60 KTs, elongating
hodographs and increasing 0-3km helicity to values in excess of
500 m2/s2.

Uncertainty remains regarding the extent and timing of low level
inversion erosion in the absence of strong surface heating. This
will largely determine the northward extent of the tornado threat
in the late afternoon, prior to steep midlevel height falls.

While some uncertainty remains regarding the onset timing of
surface-based convection and associated tornado threat, the
parameter space will become quite concerning by early Tuesday
evening, aided by CAPE in excess of 1000 J/kg and steep height
falls and strongly bowed hodographs. Low LCLs (cloud bases) and
storm movement in excess of 60 mph will make for particularly
dangerous convective environment, where tornadic storms appear to
arrive suddenly, preceded by little if any visual or audible
notice. Definitely a time to keep a weather radio with battery
backup and a fully-charged cell phone nearby.

Beyond Tuesday`s severe event, generally quiet weather is
forecast from through the upcoming weekend, under fast zonal flow
aloft. A northern branch upper low will pass through the Great
Lakes on on Saturday, modestly depressing midlevel heights over
the Midsouth and aiding the passage of a Pacific cold front. A few
showers will accompany the frontal passage, with only limited
chances for thunder.



low lcls + fast storm motion + strong tornadoes + nighttime + lack of general awareness is never what you want to see. 

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Far NW Tennessee here....one thing I can say is as we approach the 1 year anniversary of the December 10th tornado, storm awareness has increased substantially, to the point of storm anxiety in many cases. Schools have made decisions to cancel games, close early, etc. ahead of this event, ( a good call IMO).   Given a year ago I'm not sure that would have happened.  Many communities have yet to rebuild and people in this area are just on edge. 

Curious to see how far north the instability gets tomorrow. Could be a higher end event in NW TN and West KY if we get those dewpoints up...plenty of shear to be tapped into.  Glad this thread is somewhat active. 

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7 hours ago, southmdwatcher said:

Wow, hope we never have to do another March 1984/April 16 2011 Carolina's Outbreak event.........

One of the few times I've actually been scared about weather is when I was driving through the NC nighttime outbreak the Sunday after Thanksgiving in 1988 as it was forming. Couldn't see a damned thing driving west on I-40 toward a work assignnment. Next morning I woke up to news that there had been big and deadly tornadoes just a couple counties east of where I was. Spooky.

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