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Severe WX April 4th-6th, 2022 Severe Weather Threat


Haven't seen/heard too many things out of Allendale so I thought I would share this. Looks to be at least EF2 damage if structures are destroyed but if they were mobiles homes then likely no higher.
 
Lots of uncertainties with today's forecast, per FFC's (very long) AFD.

Despite a strong quasi-linear convective system sweeping through the
forecast area today, with widespread reports of wind damage and over
a dozen noted tornadic debris signatures, the area remains in a
general warm sector regime with abundant low-level warmth and
moisture. In the mid-layers (500-700 hPA), very dry air was left
behind following the storm system, which is helping to keep
scattered light sprinkles/showers from growing more upscale,
however, by noon broad southwesterly flow will increase moisture in
these levels as well and boosting PWATs from near an inch in this
morning`s special 06Z sounding to back over an inch and a half by
the afternoon for Central Georgia, setting the stage for another
potential round of severe weather.

Central Georgia, this afternoon into the early evening...

Abundant moisture return by the afternoon in the low- to mid-levels,
is going to be timed with a northward moving coastal, baroclinic
boundary and a very weak mid-level shortwave trough. This setup will
result in a rather abnormal setup for severe weather for this
region, but one that has worrisome combination of severe parameters:

* A weak shortwave will provide lower-level lift across the region,
which will act as a trigger mechanism for convective development
and will cool the mid-levels between 500-700 hPa, creating lapse
rates near 7 C/km.
* With zonal-flow in place in the mid-levels with the rapid invasion
of the shortwave later in the afternoon, offsetting effects of
advection warmer mid-level air won`t be as present as they
otherwise would in a more classic Southeastern SVR setup.
* Cooling in the mid-levels, combined with warm and very moist air
advecting in off the Gulf will create surface-based CAPE values
between 2000-3000 J/kg this afternoon.
* In general, wind profiles aloft are rather weak (0-6 km shear
values are below 30 kts) due to the weak nature of the shortwave
likely resulting in shorter-lived, popcorn-like cells that
collapse on themselves after approx an hour with very little wind
shear between 2-6 km.
* However, in the lowest 2 km, wind shear is decent with quarter-
circle hodographs providing good streamwise vorticity into
developing right-moving storms and increasing the potential for
rotating thunderstorms and spin-up circulations.

The result of all this in an environment in Central Georgia this
afternoon with no strong organizing trigger mechanism typical for a
more organized severe thunderstorm development, although mesoscale
boundaries or bands may change this. However, the parameters are
good for shorter-lived (1-2 hours) storms capable of large hail and
rapidly developing short-lived tornadic circulations. This threat
followed by cooler, drier air in the mid-levels allowing evaporative
cooling which combined with water loading will present
downburst/microburst potential as storm updrafts collapse.
Additionally, with 1-3 inches of rain previously fallen, a flooding
threat will be present anywhere heavier rain persists for prolonged
periods of time.

North Georgia, this evening into the overnight hours...

In north Georgia, a strong cold front from a more organized
synoptic system is expected to surge into for northwest Georgia just
before sunset. This will provide a stout triggering mechanism for
storm development, with stronger winds aloft more supportive of
longer-lived supercell development. The dynamics for north Georgia
during this time is everything that`s missing for Central Georgia
during the afternoon. However, despite the better dynamics the
thermodynamics are more lacking.

* The moisture return for north Georgia will be less abundant
resulting in PWATs just above an inch for the area, likely
resulting in convective storms struggling to become more robust.
* Storms in the south earlier in the day may rob some surface-based
instability in the region. With that said, forecast values of
surface-based CAPE are still expected to be above 2000 J/kg, but
begin falling after 6 PM.
* The timing of the cold front may keep storms elevated after 8 PM,
limiting severe potential.
* With these factors in mind, low-level wind profiles are much more
favorable to tornadic supercells if they can overcome the drier
air aloft. Hodographs show sickle-cell structures through 4-6 km,
with decent, but not perfect, storm-relative streamwise vorticity.
* Dry air in the mid levels, could cause strong evaporative
cooling fueled downbursts in any robust storms that do form.
These winds combined with the storm motion could create several
instances of damaging wind gusts.
Click to expand...
 
FB_IMG_1649252971067.jpg
 
The NAM 3km (below, left) shows some pretty conducive conditions for storms in North Georgia and East-Central Alabama today, whereas the HRRR (below, right) is much less so, depicting a massive hole in instability from storms in Central Georgia.
download (5).pngdownload (6).png
 
NAM 3K does develop some updraft helicity swaths from St. Clair county northeastward into northwest Georgia. We'll see what ultimately transpires today.
 
Some of the damage in Bonaire yesterday. I don't know exactly where this is, but I think it's from the neighborhoods between GA-96 and Robins AFB, which are relatively well-off areas where the homes are probably of good construction.

 
And here's another video that's from the area I mentioned above between 96 and the base.



Here's a crude map to give a rough idea of where these two videos came from. I've also seen photos of trees and power lines downed along Old Hawkinsville Rd.

3a3007215ec86dfd66ab164113c116a1.png
 
Last edited:
Showers initiating nearby on a boundary with clearing behind over N MS; currently 69/67 here, more moisture than the last couple events to work with locally but going to have to watch to see if we can get low level shear enough to work with, any local backing could make things interesting
 
Equus said:
Showers initiating nearby on a boundary with clearing behind over N MS; currently 69/67 here, more moisture than the last couple events to work with locally but going to have to watch to see if we can get low level shear enough to work with, any local backing could make things interesting
Click to expand...

Instability is definitely not an issue today. Just walked outside and the humidity smacked me the face. Felt a lot "soupier" than just a few hours ago.
 
Newest D3 trims westward extent of risk and pulled the TOR probs a little north, making the 10% zone more compact.

1649262319435.png1649262328580.png
 
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