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March 18-19th Possible Severe Wx Outbreak

If you are looking for a wrench, this is probably it. Helicity is there due to speed shear, but you lose directional shear. Very unidirectional flow aloft will probably will mean a very messy storm mode.
 

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Justin Buchinsky said:
That is a great look for storms but I have to wonder if that deep convection to the south is gonna kill moisture returns over southern VA and northern NC. Would also mean CAPE doesn't build like the model depicts.
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Yeah it’s that vs a mid level dry slot trying to clear things out
 
NAM 12km is upping parameters, let’s see if it forms a second round
 
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Snowflowxxl said:
I wouldn’t talk in absolutes. While that is usually the case ATL had a EF2 rip right through the city in 2008 and was only under a “MARGINAL” risk. Anything can happen even though we get spared far more than not.
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The one lone supercell on the ides of March South Carolina Outbreak which saw its first High Risk in Lower South Carolina on record. Phenomenal hailers and several tornadoes as storms dove SE during the afternoon and evening...
 
SD said:
So far the 18z NAMs have looked fairly ominous regionally
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Yeah that secondary round is becoming a legit issue, dry slot aloft clears things out in the mid and upper levels, low levels is a question
 
Myfrotho704_ said:
Yeah that secondary round is becoming a legit issue, dry slot aloft clears things out in the mid and upper levels, low levels is a question
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Yeah probably becomes a stout hail/wind threat for us late Thursday afternoon. Really didn't like how things are setting up on the NAMs in MS into Al. There are a few detractors there but it still looks rough out that way tomorrow afternoon and evening
 
Latest discussion from Birmingham:

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.
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SD said:
Yeah probably becomes a stout hail/wind threat for us late Thursday afternoon. Really didn't like how things are setting up on the NAMs in MS into Al. There are a few detractors there but it still looks rough out that way tomorrow afternoon and evening
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hate to say it but if the 00z NAM comes in similar, probably gonna get the high risk down there
 
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