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jaxjagman

Severe Storms 3-17/3-18

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Should be worth a thread

 Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1231 PM CDT Tue Mar 16 2021

   Valid 171200Z - 181200Z

   ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS EASTERN
   ARKANSAS...NORTHEAST LOUISIANA...SOUTHWEST TENNESSEE AND MUCH OF
   MISSISSIPPI AND ALABAMA...

   ...SUMMARY...
   A regional outbreak of severe storms is expected Wednesday into
   Wednesday night across portions of the lower Mississippi Valley into
   Alabama. Widespread severe storms capable of producing tornadoes
   (several of which may be intense), very large hail and intense
   damaging wind gusts are expected. More than one round of severe
   storms are possible across parts of Mississippi into Alabama during
   the afternoon into the overnight hours.

   ...Synopsis...

   A compact and intense upper low over the southern Plains will eject
   eastward to the Ozark Plateau/lower MS Valley on Wednesday. A
   surface low centered over northeast OK will develop east/northeast
   in tandem with the upper system. At the beginning of the period, a
   cold front will extend southward from the low across eastern OK into
   eastern TX before arcing southwest into south TX. A warm front
   draped northwest to southeast from near the MO/AR border into
   northern AL will gradually lift northward through the period. There
   is some uncertainty in how far north this boundary will lift across
   northern GA/eastern TN given strong cold air damming across the
   Carolinas until very late in the period. The cold front should push
   eastward to Middle TN/central AL and the western FL Panhandle.
   Across the broad warm sector, dewpoints in the mid/upper 60s are
   expected beneath steepening lapse rates and intense vertical shear,
   resulting in an environment capable of supporting a widespread
   severe weather outbreak. 

   ...Southern Plains to the Mid-MS Valley...

   Convection will be ongoing Wednesday morning near the surface low,
   southward along the cold front, and eastward along the northward
   retreating warm front from central AR into northern MS/AL. Any
   convection north of the warm front will be elevated and pose a
   threat mainly for large hail. However, shear profiles will improve
   through the morning and surface-based storms near the triple point
   and along the warm front are possible and will increase the risk for
   damaging gusts and a few tornadoes. Further south along the cold
   front across eastern OK into eastern TX, convection will move into
   an increasing unstable and moist environment. A line of supercells
   and line segments is expected to develop as convection moves into AR
   and approaches the Sabine Valley. All severe hazards are expected
   with this activity from Wednesday morning into the afternoon. 

   ...Lower MS Valley into AL/GA...

   Multiple rounds of intense, severe convection will be possible,
   mainly across MS/AL on Wednesday afternoon into the overnight hours.
   Convection will intensify along the eastward progressing cold front
   across central and eastern AR/LA during the late morning/afternoon
   as it encounters effective shear greater than 60 kt, MLCAPE around
   1500-2500 J/kg and midlevel lapse rates around 7-8 C/km. Fast storm
   motion, with 925-700 mb flow greater than 40 kt will support
   widespread damaging gusts with some gusts greater than 65 kt
   expected. Large hail (some greater than 2 inch in diameter,
   especially from the AR/MO border into northern LA, southwest TN and
   northern/central MS) is also expected with this activity.

   Further east across northeast LA into MS and AL a more concerning
   scenario appears possible. Most forecast guidance agrees that a
   round of afternoon thunderstorms are expected. This activity is
   expected to develop in weaker ascent, driven by heating and low
   level warm advection. Strong 0-3 km shear near 30-40 kt will already
   be in place with enlarged low level hodographs evident. Given weaker
   forcing, this activity will have an opportunity to remain more
   discrete and any cell will quickly become a supercell capable of
   producing strong tornadoes. As a 40-50 kt low level jet increases
   around 00-03z, intense supercells are expected to advance eastward
   along with the cold front across MS and into AL overnight. This will
   bring a second round of significant severe storms capable of intense
   tornadoes, large hail and intense damaging winds across much of
   MS/AL. If these trends are maintained, an upgrade to a High risk
   could be necessary with the initial Day 1 Convective Outlook at 06z
   tonight.

   ..Leitman.. 03/16/2021

   CLICK TO GET WUUS02 PTSDY2 PRODUCT

Storm-Prediction-Center-Mar-16-2021-1730-UTC-Day-2-Convective-Outlook.png

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 Day 3 Convective Outlook CORR 1
   NWS Storm Prediction Center Norman OK
   0234 AM CDT Tue Mar 16 2021

   Valid 181200Z - 191200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS EXTENDING FROM
   GEORGIA NORTHWARD ACROSS THE CAROLINAS...

   CORRECTED TO INCLUDE SIG AREA IN PROB GRAPHIC

   ...SUMMARY...
   Severe weather is expected from southern Virginia southward into
   Florida, and westward into portions of eastern Kentucky/eastern
   Tennessee Thursday.  Along with potential for hail and locally
   damaging winds, several tornadoes -- a couple of them possibly
   strong -- are anticipated.

   ...Synopsis...
   A vigorous upper low initially progged over eastern portions of the
   Ozarks, is expected to continue steady eastward progression through
   the period, weakening gradually as it crosses the Appalachians and
   reaches Virginia/the Carolinas by the end of the period.  In the
   wake of this feature, ridging will expand to encompass much of the
   country, as an eastern Pacific trough nears the Pacific Northwest
   Coast late.

   As the upper system advances, a surface low just ahead of cyclone
   aloft will likewise progress eastward, crossing the mountains during
   the evening before redeveloping offshore through the end of the
   period.  A trailing cold front will cross the southern Appalachians
   through the first half of the period, before moving offshore
   overnight.  A second day of fairly widespread -- and possibly
   locally substantial -- severe risk is anticipated.

   ...Parts of the Mid and Southern Atlantic Coast states, and westward
   into eastern parts of KY/TN...
   Showers and thunderstorms -- and some attendant severe weather risk
   -- will be ongoing Thursday morning, particularly over the southern
   Appalachians region.  With associated clouds streaming northeastward
   across the  middle and southern Atlantic Coast states, hindered
   heating -- and thus tempered diurnal destabilization -- is expected.
    Still, with northward advection of higher theta-e air east of the
   mountains ahead of the advancing surface system causing a rapid
   retreat of the remnant damming front, sufficient CAPE should evolve
   to support vigorous storms -- with intensity of the updrafts aided
   by strongly veering/increasing flow with height.  

   Storms should increase through midday west of the mountains across
   parts of eastern Kentucky/eastern Tennessee ahead of the synoptic
   system.  Relatively low-topped storms -- and local risk for
   all-hazards severe weather -- will likely evolve.

   Meanwhile, storms are expected to spread across Georgia and into the
   Carolinas ahead of the advancing cold front, along with some
   pre-frontal cellular development within a zone of strong warm
   advection east of the mountains.  Given ample instability and a very
   favorably sheared environment, relatively widespread and locally
   substantial severe weather potential is indicated -- including risk
   for a few strong tornadoes.  Potential is expected to expand
   northward toward/into southern Virginia with time as the front
   retreats into the evening, before convection begins to end from west
   to east as the cold front moves toward -- and eventually off -- the
   Atlantic Coast.

   ..Goss.. 03/16/2021
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National Weather Service Nashville TN
218 PM CDT Tue Mar 16 2021

...Severe Weather is Likely in Middle TN on Wednesday...

.DISCUSSION...

Clouds have really hung tough across the southeastern half today.
This has kept temperatures down for this area, but the sun is out in
all its glory everywhere else across the mid-state and temperatures
are responding with low to mid 70s at forecast time.

I guess you could call today `the calm before the storm` because
tomorrow and tomorrow night are going to be a different story.

If you`ve been hiding under a rock (which is uncomfortable, by the
way) for the last few days, we`ve been touting the idea that severe
weather is on the way tomorrow and nothing has really changed that
thought process. An upper level system taking shape over the
southwestern U.S. right now will continue to intensify and push this
direction overnight. As it does, a warm front will pull northward
through our region providing ample moisture for storms to feed on.
** This is where part of the narrative has changed ** We`ve been
questioning whether the warm front would pull far enough north to
provide severe weather to most of Middle TN and it looks like this
is going to happen. What this means is we`ll be dealing with three
seperate time frames of concern:

First, showers and thunderstorms will pull through the mid-state
during the morning hours tomorrow. A few of these morning storms are
going to be worth watching. There will be plenty of shear and just
south of whereever the warm front is could see some decent storms.

Second, this warm front will pull north into KY, leaving Middle TN
in a moist, warm sector during the afternoon. Latest CAM guidance is
suggesting it will be quiet and the environment will have an
opportunity to warm and destabilize further for the evening
activity. Let`s not get ahead of ourselves here. The afternoon is
going to carry with it the potential for discrete supercell
development. The bulk of this *should* remain southwest of Middle
TN. However, there is the potential we could see some development or
storms could develop to our southwest and move into our southwest
counties (south of I-40 and west of I-65) during the afternoon.
While confidence of this occurring is low, it does need to be
monitored closely. Obviously, if this occurs, tornadoes, straight
line winds and hail would be the main threat with any of these
storms.

Third, and this is the main show, storms along the cold front in the
evening hours. Even if the afternoon stuff doesn`t occur, this is
our best bet for severe weather for much of Middle TN -- and all
modes: tornadoes, straight line winds, hail (less of a chance) and
flash flooding. Main time frame is 7 pm until 2 am. Yes, 2 am.
Latest guidance has slowed the approach of these storms, which could
help things start later and linger later into the night for our
eastern counties.

Here`s the main takeaway from all of this: the bulk of this activity
is at night, which means yet another nocturnal event in Middle TN.
Please have multiple ways to get warnings (in case one way fails),
have a plan in place to shelter in a hurry, if you go under a
warning and third, you may even consider waiting until the storms
pass you before going to bed Wednesday night. This might be more
difficult east of I-65 as it`ll likely be later in the night before
storms reach you, but it could be beneficial if pinched for time
when you need to take shelter.

The cold front associated with the overnight storms should have
things off the Plateau before daybreak Thursday, however the rain is
likely not to be over. The upper trough with this system could very
well traverse Middle TN during the day on Thursday and provide an
opportunity for thunderstorms Thursday afternoon. I don`t expect
anything severe, but with the cold core of the upper low overhead on
Thursday, some hail associated with these storms is not out of the
question, especially east of I-65.

By Friday, things will quiet down for awhile. The weekend will be
dry and decent, but if you`re fan of the GFS, yet another system
could be on tap this time next week (the Euro holds off until later
in the week).

It is March and we are in severe weather season, so if you haven`t
done so already, take a minute this evening and visit
ready.gov/plan. You can get some pointers on how to prepare yourself
and your family BEFORE the storms get to you.
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National Weather Service Memphis TN
344 PM CDT Tue Mar 16 2021

.DISCUSSION...
The upper-low near the Four Corners continues to move east this
afternoon with a well-defined baroclinic leaf downstream over
the south-central CONUS. Pressure falls over the Southern Plains
suggest surface cyclogenesis. This is verified by surface obs
with a surface low and attendant triple point in northwest OK and
a quasi-stationary front extending across AR into the TN Valley.
Temperatures have overperformed by a few degrees with Memphis
recording it`s first 80F reading of 2021 (last time was Nov 8).
However, dewpoints have fallen into the 40s north of the
stationary front resulting in a very pleasant afternoon.

A few storms continue in the Starkville area, just south of the
CWA, but we do expect this activity to gradually lift north
along the warm front overnight. This convection is most likely
after midnight. Strong shear and elevated instability may be
sufficient to support a few weak, elevated supercells. With these
storms being elevated, the primary risks will be hail up to the
size of quarters and locally heavy rainfall. This convection will
continue to lift north throughout the morning hours and is
expected to reach the I-40 corridor after sunrise. Large scale
forcing for ascent will be overspreading the CWA, steepening mid-
level lapse rates and enhancing lift provided by warm advection
and improving jet dynamics.

Most of the convection by midday is expected to be in east AR or
west TN with the warm sector across north MS likely seeing a bit
of a lull. This lull will be important for destabilization. If
we see a sufficient dry period, SBCAPE should be able to increase
to 1500-2000 J/kg south of the warm front, whereas areas that
remain in the muck will be see much more limited buoyancy. Shear
will be quite strong with 0-6 km bulk wind difference near 60 kts.
A few supercell structures are possible within the AM gunk, but
will be more probable during the afternoon and evening hours where
instability is stronger. If low-level warm advection and large
scale ascent is sufficient to erode the cap, discrete supercells
will be possible in the warm sector ahead of the cold front. This
is the time for the greatest risk for strong (EF2+) tornadoes and
sig hail (2+ inches).

The cold front will approach the MS River after 00z, but storms
are expected to develop along a pre-frontal trough during the
mid/late afternoon hours. Strong line-normal shear will promote
upscale growth, eventually forming into a QLCS. This QLCS will
remain in a favorable environment for tornadoes and damaging
wind as the low-level jet begins to intensify, but the large hail
threat will begin to decrease. Several CAMs are representing 0-1
km storm relative helicity at or above 250 m2/s2 with Significant
Tornado Parameter values of 1-3. As the line moves into west TN
and north MS, we`ll maintain the risk for QLCS tornadoes and
mesovortices. These tornadoes can develop quickly and it can be
difficult to provide much lead time, especially far from the
radar. Given the potential for nocturnal tornadoes, it is
important to plan ahead and ensure you are capable of receiving
timely weather alerts. In addition to the severe weather threat,
locally heavy rainfall is possible. We`re looking at widespread
1-2" with localized higher amounts.

This activity will largely end by 06z, but there may be some
lingering showers and thunderstorms during the early morning
hours. As the upper-low moves across the region on Thursday,
expect scattered rain showers, mainly north of a Jonesboro-
Savannah line. QPF with this precipitation should remain under
1/4 inch. Cooler and drier air will accompany Wednesday night`s
cold front and will be ushered in by strong west winds. Wind gusts
on Thursday may exceed 30 mph at times.

Expect dry conditions and slightly below normal temperatures on
Friday with highs in the low/mid 50s. Given the dry air and clear
skies, it`s possible that some areas will experience a frost
Saturday morning. We`ll continue to monitor these trends for the
weekend. Otherwise, temperatures will moderate over the weekend
with dry conditions continuing through Sunday. Rain chances return
next week. More details on that system as it approaches.
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National Weather Service Birmingham AL
308 PM CDT Tue Mar 16 2021

.SHORT TERM...
/Updated at 0308 PM CDT Tue Mar 16 2021/
Through Wednesday morning.

A wedge front is causing some chilly temperatures across the
northeast counties this afternoon, with a milder and more humid
air mass southwest of it. An effective warm front/low-level
confluence axis across our southern counties is causing some
training showers and storms there, aided by ripples in the
southwest flow aloft. This activity will continue to cause locally
heavy rainfall amounts across the south. Low streamflow values
will mitigate the flooding threat somewhat, but some isolated
flash flooding will be possible mainly in urban areas or if
additional heavy rainfall moves into areas of our southwest
counties that have already received 3 to 4 inches of rainfall.
Effective shear values around 50 kts have resulted in a few
rotating storms across our south this afternoon which could
produce localized hail or damaging winds. Low-level SRH is
marginal until you get further north to the wedge front, so while
the threat for a brief tornado is non-zero, it is low. Further
north, clouds are limiting instability. Severe potential further
to the north seems fairly low, but will leave it in for the
afternoon for now with some clearing occurring in our northwest
counties. May get a lull in activity tonight with the loss in
daytime heating before activity increases after midnight as the
effective warm front lifts northward and another weak shortwave
moves through. Most of the activity will be along and north of the
warm front, with elevated instability and shear supportive of
some hail and gusty winds. But if a storm is able to be rooted
near the surface along the warm front, there will be a low but
non-zero threat of an isolated tornado across the north early
Wednesday morning. With a more significant threat later in the day
on Wednesday, won`t be including this on our messaging at this
time but will continue to monitor.

32/Davis

.LONG TERM...
/Updated at 0308 PM CDT Tue Mar 16 2021/

**Significant severe weather outbreak expected Wednesday and
 Wednesday night**

Overall little change to the forecast thinking, with a relatively
long duration and significant severe threat for all modes of
severe weather.

A potent and compact low-amplitude trough will move from the
Southern Plains on Wednesday to the Lower Mississippi Valley
Wednesday night, preceded by a 60-80kt mid-level speed max and a
40-50kt LLJ. A 998mb surface low will track from Oklahoma to
Illinois with a broad warm sector with mid to upper 60s dew points
in advance of a cold front. Shortwave ridging/anti-cyclonic flow
aloft is forecast to develop Wednesday morning which should allow
the early morning showers/storms to move out of the area. This
will allow for heating and ample destabilization. CAPE values will
increase to 2000 to 3000 J/kg across much of the area by
afternoon. Forecast soundings indicate the air mass across the
warm front will be uncapped across the warm sector by afternoon,
and CAMs are in fairly good agreement on scattered to perhaps
numerous supercells developing in the 1 to 4 PM timeframe. Low-
level SRH is less than 200 m2/s2 initially during the afternoon,
so large, potentially significant hail may be the main threat
initially with 50 to 60kt of 0-6km shear aiding updraft rotation,
but a couple isolated tornadoes will still be possible. For
simplicity, will start the threat time at 2 PM everywhere to
account for this activity. After 4 PM, the 850mb jet and
associated SRH begins to really ramp up across West Alabama, and
across the rest of the area by 6 to 7 PM. This is when concern for
strong, potentially long track tornadoes will begin to ramp up
with any semi-discrete supercells still present. We will also be
monitoring mesoscale trends closely for the possibility of a
violent tornado. It`s hard to find too many limiting factors for
this event, but if I had to mention one it might be if too many
storms get going too early before the low-level shear increases.
However with the strong low-level jet and activity remaining
cellular I don`t see this being much of a limiting factor. Will
also need to monitor the northward movement of the wedge front. It
could limit the afternoon threat across some of our far northeast
counties, but also serve as an additional source of helicity for
storms near the warm side of it. I do expect the wedge front to
exit the area prior to the overnight activity.

During the late evening and overnight hours, another strong line
of storms will move in from the west ahead of the cold front.
Shear vector orientation has a component normal to the line and
the magnitude is strong as well. This will be favorable for
embedded supercells in the line or a semi-broken line of
supercells, therefore this activity will also be a concern for
strong to intense long-track tornadoes, not just weak QLCS spin-
ups. Additionally, any bowing segments will have a significant
wind threat as well. Outside of storms, gradient winds near 35 mph
will be possible, and will monitor for the possible need for a
wind advisory. Activity will remain fairly progressive and
antecedent conditions still fairly dry, limiting the overall
flooding threat, but some minor flooding in poor drainage areas is
possible, and some rivers are forecast to be near or above flood
stage.

The rest of the previous long term discussion remains valid.

32/Davis

Previous long-term discussion:
/Updated at 0311 AM CDT Tue Mar 16 2021/

Thursday through Sunday.

Storms will likely be ongoing Thursday morning across east
Alabama, but should be in a weakening trend. Should see some
clearing skies during the day Thursday as drier low level air
moves in behind exiting cold front. However, strong cold air
advection will also bring low clouds back into the area Thursday
afternoon, starting in the west and spreading eastward. A much
colder air mass Thursday night and into weekend with temperatures
back closer to normal values. May not see much sunshine Friday as
cyclonic circulation keeps low level moisture in the area. A few
sprinkles not out of the question on Friday as an upper level
vort lobe pushes down from the north. Partly cloudy over the
weekend with a gradual warming trend.

58/rose
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SPC saying they may upgrade to a high risk for the Day 1 outlook late tonight.

Hope everyone in the path of this system stays safe!

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Folks in SE TN shouldn't sleep on this system..while nowhere near as robust as AL/MS, there is a potential for a lower end tornado across that area..excellent write up from MRX.

 

Confidence has increased a bit for severe convection over the S half
of the CWA Wed night, but uncertainty still exists regarding both
how far N and how quickly the warm front will advance into our
region which determines where the surface instability gradient will
be. The mid/upper closed low and surface low complex will lift
toward S IL Wed night with the surface low deepening to about 995
mb. As this occurs, the upper jet rounding the E side of the system
will strengthen to 100-110 kts and shift over the TN Valley and S
Appalachians causing the LLJ to strengthen to 50-70 kts. This will
support strong WAA and moisture transport, as well as strong
frontogentic forcing along and north of a northward advancing warm
front. The last few runs of the NAM are outliers in keeping the warm
front S of our region, whereas the RAP, HRRR, and deterministic GFS,
ECMWF, and CMC lift the front and associated theta e/dew point into
the S Plateau and SE TN in the 06-12Z timeframe. This front is the
wild card. Scattered strong to severe thunderstorms will be ongoing
across AL and GA early Wed night as this front lifts N, as well as a
squall line farther W near the eastward advancing cold front. Strong
deep layer shear of 50-70 kts+, 0-1 Km shear of 40-50 kts, and
strongly veered wind profiles N of the warm front characterized by 0-
1 Km SRH of 400-600 M2/S2 and curved hodographs support a
potentially volatile environment that could support tornadoes as
well as large hail and damaging winds. However, areas N of the
warm front will not have any surface instability (all elevated)
and the LCL heights will be too high N of the warm front. This
means that tornado potential is limited to areas where the warm
front can make it to (likely the S Plateau into SE TN) where areas
farther N will only see elevated convection with pockets of hail
and damaging winds. In terms of timing, the severe weather threat
should generally be 06-09Z over the S Plateau and S Valley (W of
I-75) and 07Z-11Z over the rest of SE TN and SW NC. Overall,
confidence is high that we will see pockets of damaging winds and
hail, but the confidence on tornadoes is low. Repeated rounds of
convection could start to cause localized flooding issues by late
Wed night, especially over the S half of the region where total
rainfall of 1-2 inches is possible. Finally, the strong 50-70 kt
LLJ Wed night will lead to high winds in the E TN mountains and
foothills. Issued a High Wind Watch for this potential (see
product for details).
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Oh just wonderful! Reads like the Midnight Easter 2020 Chattanooga just-in-time instability, with ridiculous deep layer shear, and ludicrous low level shear tornado. 

In March the warm front should have less of a chance of making it into southeast Tennessee overnight, compared with in April. However Wednesday night is a dynamic system bringing in plenty of warm advection.

Biggest concern is Alabama strong tornadoes deep into the overnight hours Wednesday night, perhaps well past Midnight.

More tomorrow about Daytime locations such as the Delta and Mid-South.

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Warm front looks pretty healthy this AM:
giphy.gif&key=1cea355b27b1e68e89a4ebc57ff7376d6ab65a545fc25359b6e6c07d2a043c7e
 
High Risk in effect now:
QAFLqko.png&key=3d4b0a92198dc96d98c9b3304afca2a8a3439cd096432826fb2e1d4f5d9f454a
 
qi5NbSr.png&key=f9a2a751449e696c1a53c7953da0a48deaa8068db134ecf99fa403a105056191

That WF is moving faster than I expected.


.
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Does the SPC outlook go into the overnight hours? 
 

I’ve heard a variety of answers but I feel like this forum will have the best answers. TIA.

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42 minutes ago, Scottie16 said:

Does the SPC outlook go into the overnight hours? 
 

I’ve heard a variety of answers but I feel like this forum will have the best answers. TIA.

Yes.  It goes from 12z to 12z if I remember correctly

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42 minutes ago, Scottie16 said:

Does the SPC outlook go into the overnight hours? 
 

I’ve heard a variety of answers but I feel like this forum will have the best answers. TIA.

Generally yes,until midnight CST,then the next day takes over

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Particularly Dangerous Situation Tornado Watch upcoming for central Mississippi and Central Alabama! Rapid destabilization in progress. Shear is already higher than progged, per observed soundings. Outflow boundary separated from warm front, south of cooler sector. Coastal theta E surge (and wind shift) is rushing north too. That's not one, but two boundaries to enhance low-level shear.

This does not get Mississippi and Alabama out of the overnight threat. Atmosphere will still get even worse as the second line slams in tonight. Low level jet strengthens over Alabama tonight, increasing shear even more. CAPE maintains positive. Yes @Scottie16 it goes through 6am Thursday morning. Make sure you have two LOUD ways to get notified overnight. Weather Radio AND a subscription App. Free usually notifies too slow. 

52 minutes ago, Scottie16 said:

Does the SPC outlook go into the overnight hours? 

REVISED from yesterday: I believe these boundaries in the free warm sector are the bigger daytime threat. Previously I considered the line out of Arkansas the main show. However that second line will be a dangerous problem for Mississippi this evening. Alabama faces a tornado threat all night, including strong long-track tornadoes through 3am. Any tornadoes are possible all the way until 6am Thursday.

Tennessee is also at risk. Entire Mid South will explode this afternoon into southwest West Tenn. Middle Tennessee will probably get categorial upgrade (from where a certain location was before). Southeast Tennessee and North Georgia is in play tonight, unfortunately. 

https://www.spc.noaa.gov/products/md/md0200.html

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51 minutes ago, Scottie16 said:

Does the SPC outlook go into the overnight hours? 
 

I’ve heard a variety of answers but I feel like this forum will have the best answers. TIA.

Try this

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28 minutes ago, nrgjeff said:

Particularly Dangerous Situation Tornado Watch upcoming for central Mississippi and Central Alabama! Rapid destabilization in progress. Shear is already higher than progged, per observed soundings. Outflow boundary separated from warm front, south of cold sector. Coastal theta E surge is rushing north too. 

This does not get Mississippi and Alabama out of the overnight threat. Atmosphere will still get even worse as the second line slams in tonight. Yes @Scottie16 it goes through 6am Thursday morning. Make sure you have two LOUD ways to get notified overnight. Weather Radio AND a subscription App. Free usually notifies too low. 

REVISED from yesterday: I believe these boundaries in the free warm sector are the bigger daytime threat. Previously I considered the line out of Arkansas the main show. However that second line will be a dangerous problem for Mississippi this evening. Alabama faces a tornado threat all night, including strong long-track tornadoes through 3am. Any tornadoes are possible all the way until 6am Thursday.

Tennessee is also at risk. Entire Mid South will explode this afternoon into southwest West Tenn. Middle Tennessee will probably get categorial upgrade (from where a certain location was before). Southeast Tennessee is in play tonight, unfortunately. 

https://www.spc.noaa.gov/products/md/md0200.html

That is a huge area for a PDS

URGENT - IMMEDIATE BROADCAST REQUESTED
   Tornado Watch Number 29
   NWS Storm Prediction Center Norman OK
   1135 AM CDT Wed Mar 17 2021

   The NWS Storm Prediction Center has issued a

   * Tornado Watch for portions of 
     Western and central Alabama
     Central to eastern Mississippi

   * Effective this Wednesday morning and evening from 1135 AM until
     700 PM CDT.

   ...THIS IS A PARTICULARLY DANGEROUS SITUATION...

   * Primary threats include...
     Numerous tornadoes expected with a few intense tornadoes likely
     Scattered damaging winds and isolated significant gusts to 80
       mph likely
     Scattered large hail and isolated very large hail events to 3
       inches in diameter likely

   SUMMARY...Numerous discrete supercells are expected to develop this
   afternoon capable of producing strong to intense tornadoes.

   The tornado watch area is approximately along and 80 statute miles
   east and west of a line from 70 miles northwest of Gadsden AL to 35
   miles southeast of Pine Belt MS. For a complete depiction of the
   watch see the associated watch outline update (WOUS64 KWNS WOU9).

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I don't like the storm motion. They are all aimed straight up I-59 directly at SE TN. We really need that warm front to remain where it is. 

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