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Severe Weather 2021

Fred Gossage

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It makes me wonder why these weather experts say the things they do.
I assure you that it was not an "expert" who said that, by any remote stretch of the imagination....

And if it WAS a person who has the credentials to be considered an "expert" and they are saying things like that, they don't deserve said credentials...
 

JBishopwx

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NWS Jackson already mentioning a chance, although not that high for now, for the weekend: mesonet.agron.iastate.edu/wx/afos/p.php?pil=AFDJAN&e=202104052013
So, while we can`t get into specifics on the late week/weekend in terms of what/when/where, expect something and we will add threats to the HWO graphics as confidence increases.
 

MattW

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The hi-res NAM shows some interesting potential for Alabama on Thursday afternoon. The sounding is a box-averaged sounding around the Selma-Montgomery area. I know it's the extreme end of the range for the hi-res NAM.
 

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Timhsv

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327 PM CDT Tue Apr 6 2021


Edited for emphasis:

In general terms, the latest global guidance continues to come into
better agreement on storm potential as we move into the end of the
week. Yesterday there was more variability and solutions supporting
a couple rounds from later Thu into late Sat. Now, solutions are
converging more on one main event in the Fri afternoon and night
periods with potential for some pre activity later Thu night into
early Fri. This increased agreement is mainly driven by the energy
moving into the PacNW on Thu then becoming more phased as it drops
into the mean trough axis on Fri over the central CONUS. As all of
this occurs, our region will see a return of low level moisture
later on Thu and into Fri as more response takes shape with the
development of a sfc low over the Red River Valley. All this occurs
under cold temps aloft which will promote steep to very steep lapse
rates (VT of 29-31c
). Additionally, the upper jet structure will be
very supportive with strong left exit dynamics in play and quite a
bit of potential vorticity in the upper levels. Additionally,
various cape outputs show energy in the 2500-4000 j/kg range. With
these elements, vigorous updrafts are likely. In terms of kinematics,
low and midlevels are not strong like the upper jet. However, latest
trends have show more of a develop/deepening sfc low which will
likely contribute to increased low level shear.
Much of this will
hinge on sfc front position and magnitude of deep ascent to aid in
the reality of where a sfc low will track. Finally, the qpf response
from the global models has quite the intense signal resulting in
large disruptions to the model fields. This is a feedback response
and often wreaks havoc on downstream forecasts. However, it also is a
signal on on the volatility in the potential environment which is
supported by some of the high end elements.

To summarize, the system for late week looks to be quite potent and
the underlying environment will be primed and supportive of
significant severe storms
. Specific timing is too tough to cover,
but a broad window of multiple storms is becoming likely any time
from late Thu night, Friday and into the early morning hours of Sat.
Due to the potential for some high end severe storms, we wanted to
highlight this threat in our HWO and issue a graphic. While we are
starting with a "Slight" risk, anticipate this to increase along
with locations and timing to adjust as more information is know and
confidence in the specifics increases.
Additionally, with multiple
storms, heavy rainfall and flash flooding may also become a threat.
This will be something we can focus more on as we get closer and
have a better idea of the complex storm evolution and potential for
where repetitive storms may be more likely.
 
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Very large slight risk area out for Day 3 and a risk for Day 4 that both just kind of came out of nowhere. If this is what this spring does when the MJO is in an unfavorable phase... :eek:
 

Bama Ravens

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BMX is discussing 3 potential rounds of severe weather over the next few days: (1) tonight/tomorrow morning; (2) tomorrow night and Friday; (3) late Friday night and Saturday morning.

None of these sound like major tornado threats, and Friday sounds like it could be a very conditional threat with hail possibly being the main issue due to a lack of forcing and low shear. The Saturday morning round appears to come in the form of an MCS, but where exactly that goes is still uncertain.
 

MattW

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Am I seeing the NAM Hi-res right? At 18z on Thursday it's showing a big area of SigTor for central Alabama, but almost no updraft helicity swaths. I don't think I've ever seen that before.
 
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Am I seeing the NAM Hi-res right? At 18z on Thursday it's showing a big area of SigTor for central Alabama, but almost no updraft helicity swaths. I don't think I've ever seen that before.

Looks like it's not developing robust convection over the area with high SigTor values. It would stand to reason that without sustained, vigorous updrafts, there can't be updraft helicity. As to why it's not developing convection, I'm not sure. It shows no capping in the form of CIN, but looking at soundings it looks like there is a quite dry layer between 850-700mb that may be acting as some sort of cap.
 

Clancy

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Friday into Saturday on the 3K NAM looks bizarre. Some really widespread high CAPE values Friday afternoon/evening. Going by CAPE alone, almost reminds me of summer days.
1617810018805.png
 

keithGA

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Rather large 2% tornado area for tomorrow.
 

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TH2002

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TOR for the storm west of Danville, AR

UPDATE: TOR has been cancelled and replaced with SVR
 
Last edited:

WhirlingWx

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Rare D3 update just now, to add an enhanced risk for parts of Mississippi and Louisiana.

"AN ENHANCED RISK WAS ADDED TO PORTIONS OF NORTHEAST LOUISIANA AND
CENTRAL AND SOUTHERN MISSISSIPPI. A SOUTHERN STREAM MID-LEVEL
SHORTWAVE TROUGH IS FORECAST TO AMPLIFY DURING THE EVENING HOURS ON
FRIDAY ACROSS EAST TEXAS AND LOUISIANA. IN RESPONSE, THE LOW-LEVEL
JET IS EXPECTED TO INCREASE DURING THE EVENING/EARLY OVERNIGHT HOURS
ACROSS LOUISIANA AND MISSISSIPPI. THIS STRENGTHENING LOW-LEVEL JET
SHOULD INCREASE THE THREAT FOR DAMAGING WINDS AND TORNADOES DURING
THE LATE OVERNIGHT FRIDAY AND EARLY MORNING HOURS SATURDAY ACROSS
MAINLY CENTRAL AND SOUTHERN MISSISSIPPI."
 

TH2002

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And the storm just went TOR again, fortuntately no tornadoes reported from this cell. New TOR in MO
 

Tennie

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New thread has been set up. Let's discuss the current weather situation over there:

 
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