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Severe 3/30-4/2 Severe Weather

DAY 2 TEXT - GOT SOME STRONG WORDING

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1254 AM CDT Tue Mar 29 2022

Valid 301200Z - 311200Z

...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF LOUISIANA...MISSISSIPPI...AND ALABAMA...

...SUMMARY...
A regional outbreak of severe thunderstorms is expected on Wednesday
across the Lower Mississippi Valley and Southeast States. All severe
hazards are possible, including significant gusts over 75 mph and
strong (EF2+) tornadoes.

...SEVERE-WEATHER OUTBREAK POSSIBLE ACROSS PORTIONS OF
LOUISIANA...MISSISSIPPI...AND ALABAMA...

...Synopsis...
A strong southern-stream shortwave trough is forecast to extend from
central KS through the TX Hill Country early Wednesday morning. This
shortwave is expected to progress eastward/northeastward throughout
the day, becoming increasingly negatively tilted as it does. Strong
mid-level flow will accompany this through, with 100+ kt at 500 mb
stretching from southeast TX northeastward through the Mid-South
Wednesday afternoon. Additionally, very strong low-level flow will
precede this feature, with a large area of 60+ kt at 850 mb expected
across the MS Valley Wednesday afternoon.

Low-level moisture advection will also precede this shortwave
trough, bringing at least low 60s dewpoints through the Mid-South/TN
Valley. Upper 50s dewpoints will likely reach into the Lower/Middle
OH Valley. These dewpoints will help foster at least modest buoyancy
and thunderstorms are anticipated as the shortwave ejects
northeastward over this moist and buoyant airmass. Given the
strength of the wind fields, severe thunderstorms are likely,
particularly across portions of the Lower MS Valley and Southeast
where a regional outbreak of severe thunderstorms is anticipated.

...Lower MS Valley into the TN Valley and Southeast...
A line of thunderstorms will likely be ongoing from the Ozark
Plateau southwestward into East TX early Wednesday. Expectation is
for this line of storms to quickly move eastward, outpacing a cold
front moving southeastward into the MS Valley. Widespread clouds
will limit diurnal heating downstream of this line of storms, but
strong moisture advection will still result in at least modest
buoyancy and airmass destabilization. At the same time, wind fields
will strengthen considerably. This combination of buoyancy and very
strong wind shear is forecast to result in a strengthening of the
line as it moves into eastern AR and LA during the early afternoon,
before then continuing quickly eastward across MS and AL during the
evening and overnight.

The kinematic fields, especially in the low-levels around 850 to 700
mb, are forecast to be very intense. Mean wind speeds from the HREF
show a corridor of 70 kt at 850 mb from central LA into southeast AR
at 18Z. Deep-layer mean winds are forecast to be 65+ kt across much
of LA, MS, and AL as the line moves through. Expectation is that
these robust wind fields will result in an intense convective line
capable of widespread wind damage. Embedded/QLCS tornadoes are also
likely within this environment, including the potential for strong
tornadoes (EF2+). Fast storm motion could result in longer-track
QLCS tornadoes than are typically observed.

In addition to the strong wind gusts and embedded QLCS tornadoes,
discrete supercells ahead of and/or south of the primary convective
line are also possible. Any discrete storm that is able to mature
and deepen would likely become an intense supercell capable of
producing severe wind gusts and strong tornadoes. However, the
forcing for ascent and fast-moving character of the shortwave (as
well as the convective line) do not favor a discrete convective
mode, and the current expectation is for the linear mode to
dominate.

..Mid MS and Lower/Mid OH Valleys...
Less low-level moisture and buoyancy is anticipated in the region
compared to farther south. However, strong forcing for ascent should
help maintain the convective line as it moves eastward through the
region. Strong wind fields support the potential for damaging wind
gusts with any deep convection, even in areas that exhibit shallow
low-level stability.

..Mosier.. 03/29/2022
 
TEXT FROM NWS BMX

National Weather Service Birmingham AL
401 AM CDT Tue Mar 29 2022

.SHORT TERM...
/Updated at 0327 AM CDT Tue Mar 29 2022/

Wednesday and Wednesday night.

* A significant damaging wind event is possible across Central
Alabama Wednesday afternoon into Wednesday night with straight-
line gusts of 60-70 mph. A few tornadoes are also possible.

* Non-thunderstorm wind gusts of 40-50 mph are possible during the
afternoon and evening ahead of the thunderstorm complex. This
could lead to tree fall and resultant damage to property and to
power outages.

By tomorrow morning, the trough to our west will amplify and begin
to swing from a positive to a more neutral tilt. An ongoing MCS will
then advance east from the ArkLaTex toward the lower Mississippi
Valley. By the afternoon, the shortwave is expected to swing to a
more negative tilt as both mid-level and low-level jets intensify.
The southerly LLJ will position across the Deep South during the
afternoon featuring 850 mb flow of 60-70+ kts, and 925 mb flow of 50-
55+ kts. A tight pressure gradient will combine with this strong LLJ
leading to windy conditions in the afternoon given expected BL
mixing. 40-50 mph gusts will be possible, and this could be quite
problematic given vulnerability to fallen trees in the region.

The LLJ will coincide with a narrow warm sector containing dewpoints
rising into the low to mid 60s, especially into the evening. Highest
values likely stay just ahead of the incoming MCS/QLCS. This
moisture will combine with afternoon heating to foster MLCAPE of 500-
750 J/kg across MS, where the system is expected to gain intensity
and forward speed. The combination of upper-level forcing/dynamics
and increasing instability within abundant kinematics will result in
a elongated area of thunderstorms capable of producing 60-70 mph
wind gusts. The robust LLJ will also support broad hodograph
curvature with 300-400 0-1 km SRH, and higher values in the 0-3 km
layer. Line-embedded bowing segments/circulations are likely - areas
where 0-3 km shear vectors can become line-normal in particular.
These features will lead to the greatest damaging wind threat, with
a few embedded tornadoes as well. Given the aggressive nature of the
MCS/QLCS, damaging wind gusts could be quite widespread across
Central Alabama throughout late Wednesday afternoon into Wednesday
night. At this time it appears areas along and north of I-59 have
the best dynamics/wind energy to work with, and it is here where the
most severe potential exists. However, instability continues to be a
limiting factor as it generally wanes in the evening. Areas west of
I-65 have the best chance of meaningful CAPE to promote stronger
thunderstorms/stretching. It is unclear how far east of I-65 the
warm sector can go before the convective system out runs it.
Nonetheless, all of Central Alabama is poised to see risk, and it
could be that wind energy/forcing overcomes limited instability for
most of our area. The convective line is expected to gradually
weaken later Wednesday night as forcing/dynamics aloft pull to the
north. This line should "lay over" and become more parallel to flow
aloft, slowing it`s progress and leading to areas of higher rainfall
potential along and south of I-85. The severe threat will continue,
however. By ~6 AM, the system should exit Central Alabama. 1-2" of
total rainfall is expected, with locally higher amounts. Some flash
flooding will be possible.

40/Sizemore
 
TileDude said:
NWS is forecasting possible widespread wind damage and Spann is calling it a high empact event. Very strong wording for our area.
Click to expand...
Yeah I need to secure a lot of stuff by my house. Id consider residing in a structure built house or building, very strong straight line winds are just as akin to a weak tornado which can often lift and throw mobile homes.
 
This is from James Spann morning discussion.

CALL TO ACTION: This has potential to be a high end wind event for much of Alabama; plan for power outages. Secure loose objects that might go flying away with strong winds. Pay close attention to severe thunderstorm warnings tomorrow night; if you live in a mobile home I would consider treating a severe thunderstorm warning like a tornado warning and be in a community shelter or business that is open and available as a shelter. Be sure you have two reliable ways of hearing warnings (NEVER a siren)… a NOAA Weather Radio and your phone; and be sure emergency alerts are enabled on your phone. Have the free ABC 33/40 weather app installed.
 
TileDude said:
This is from James Spann morning discussion.

CALL TO ACTION: This has potential to be a high end wind event for much of Alabama; plan for power outages. Secure loose objects that might go flying away with strong winds. Pay close attention to severe thunderstorm warnings tomorrow night; if you live in a mobile home I would consider treating a severe thunderstorm warning like a tornado warning and be in a community shelter or business that is open and available as a shelter. Be sure you have two reliable ways of hearing warnings (NEVER a siren)… a NOAA Weather Radio and your phone; and be sure emergency alerts are enabled on your phone. Have the free ABC 33/40 weather app installed.
Click to expand...
That Alabama state line area could see a high risk upgrade for wind damage, that would be the most likely. It's been a longggggg while since we've seen a sizeable derecho. Last one I remeber was summer of 2012 I think?? But wasn't even that strong. I vaguely remeber something from around 2017 I think as well
 
One thing that I (and a few others in my group chat) have been surprised at is how reluctant the SPC can be at times to upgrade risks when it is glaringly obvious that there's going to be a squall line with broad geographic coverage and the storm reports map is going to show a multi state area painted blue with some red dots and black squares. I've noticed they like to keep them at enhanced even though it's pretty likely a moderate risk will verify (or even high risk if you go by the by-the-book definition) and it's nice to see them respecting the potential here.

I am somewhat wary of the eastern sections of the board chances for mischief on Thursday- seems like another case where we are dependent on where the thickest convective debris goes.
 
ILMRoss said:
One thing that I (and a few others in my group chat) have been surprised at is how reluctant the SPC can be at times to upgrade risks when it is glaringly obvious that there's going to be a squall line with broad geographic coverage and the storm reports map is going to show a multi state area painted blue with some red dots and black squares. I've noticed they like to keep them at enhanced even though it's pretty likely a moderate risk will verify (or even high risk if you go by the by-the-book definition) and it's nice to see them respecting the potential here.

I am somewhat wary of the eastern sections of the board chances for mischief on Thursday- seems like another case where we are dependent on where the thickest convective debris goes.
Click to expand...
Probably because when the public thinks high risk they think tornado outbreak where their life is in peril vs a solid wind event that knocks out power and takes down a few trees. I believe you could get a good derecho with 200 reports of 60mph, but unless you have lots of trees fall on cars and houses the public would think a High risk would be a bust.
 
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