• Welcome to TalkWeather!
    We see you lurking around TalkWeather! Take the extra step and join us today to view attachments, see less ads and maybe even join the discussion.
    CLICK TO JOIN TALKWEATHER

Severe WX Severe Weather Threat 3/14-3/16

JPWX said:
I will say that the biggest problem with 2011 was 2 things:
1. April you had at least one significant to major outbreak each week.
2. You ended up getting warning fatigue and overload.
Those are 2 key things that ended up making 4/27 worse as far as fatalities.
Click to expand...
I believe in my heart what happened in New Orleans with Hurricane Ivan contributed to why more people stayed for Katrina. The Hurricane Ivan evacuation was a disaster. That said, I am not sure that the inaccuracy of how that all played out will happen in the modern forecasting age. Sadly, I believe ignorance will always be cause of fatalities.
 
UncleJuJu98 said:
Nam bombs out the low pressure as it moves from west Mississippi through extreme north Alabama, 994 mb to 988 in 3 hours
Click to expand...
Careful with that. The synoptic secondary surface low will actually likely track from Arkansas to the Ohio Valley in the left exit region of the second shortwave in the trough. What you're seeing is the NAM modeling supercells so intense that it thinks their mesocyclones are mesolows because of its grid resolution limitation and the fact it uses parameterizations instead of convection-allowing schemes. This is actually disrupting the LLJ evolution modeled at face value because of it.
 
Fred Gossage said:
Careful with that. The synoptic secondary surface low will actually likely track from Arkansas to the Ohio Valley in the left exit region of the second shortwave in the trough. What you're seeing is the NAM modeling supercells so intense that it thinks their mesocyclones are mesolows because of its grid resolution limitation and the fact it uses parameterizations instead of convection-allowing schemes. This is actually disrupting the LLJ evolution modeled at face value because of it.
Click to expand...
Good lord, yeah I just realized that looking at the precip. depiction.
 
Smokedevil said:
What makes 2011 stand out, is this is suppose to be the modern age with instant warnings, yet several people still died.
Click to expand...

I’m sure you know this, but I post this to just clarify to new folks…and to give the newbies the perspective of why folks in the Southeast are so sensitive to this day. “Several people died” equates to “324 people died”
 
Fred Gossage said:
Careful with that. The synoptic secondary surface low will actually likely track from Arkansas to the Ohio Valley in the left exit region of the second shortwave in the trough. What you're seeing is the NAM modeling supercells so intense that it thinks their mesocyclones are mesolows because of its grid resolution limitation and the fact it uses parameterizations instead of convection-allowing schemes. This is actually disrupting the LLJ evolution modeled at face value because of it.
Click to expand...
Christ amighty.
 
Smokedevil said:
What makes 2011 stand out, is this is suppose to be the modern age with instant warnings, yet several people still died.
Click to expand...

Part of what made 2011 so bad was because the morning line that came through knocked out power and damaged a lot of buildings, and I believe knocked out cell service in some places, I mean if not for the outbreak later that day, that line would’ve been much more notorious but yeah by the time the main event came a lot of people didn’t have ways of getting weather warnings, while 2011 was a modern time, it was also almost 15 years ago and back then there was still a number of people that didn’t have smartphones or laptops or high speed internet.
 
Friday now really starting to look like a very widespread severe weather day too - moisture has trended upwards on the NAM in the last few runs, likely both because it's catching up on its cooler bias and also a possible hint that the wave today isn't as damaging to moisture return as thought (note the trend from SE to S surface winds). The globals haven't quite caught on to this trend yet but by tomorrow morning, if we do see a proper shift, things will likely be clear by then as tonight's severe threat will have passed.

Regardless, as the mid-upper level cold pool starts to impinge on the warm sector from MO/IL up into IA, expect rapid development of powerful supercellular thunderstorms which quickly develop into a QLCS with embedded mesocyclones. Current simulated reflectivity from the models indicate an arced band of storms pretty much following the boundary of the cold pool in red which would make plenty of sense. Would be a pretty notable large hail risk, especially into Iowa where low level shear is a little weaker and those 500mb temps are coldest.

trend-nam-2025031218-f039.sfctd_b-imp.conus.gif1741811456184.png

Tornado threat seems fairly uncertain mainly due to questions about storm mode and surface moisture quality. Too much dry air at the surface could over strengthen downdrafts early on, though I'm wondering if due to the strength of the storm relative inflow this may be balanced somewhat. By about 00z though, moisture depth improves and given the wind shear - which looks to be perpendicular to the line of storms, especially across E/NE MO, we could see an environment extremely supportive of long tracked, potentially strong, QLCS circulations and embedded mesocyclones. I honestly think for a maximized tornado risk you might want storms close to or within the line of storms as opposed to completely discrete, which would limit the effect of wind shear ripping updrafts apart.

1741811961735.png1741812594502.png
Greatest threat will almost undoubtedly be the wind threat though. Whilst obviously not the same, the positioning of that jet core literally right behind the line of storms almost acts as a synoptic scale RIJ, and especially when the boundary layer is drier early on your downdrafts are going to massively accelerate as they hit towards the ground and become very powerful. We honestly could have a full on derecho from MO into IL which is probably quite uncommon for this time of year.

There is then the more uncertain southern mode, which the SPC seems fairly bullish on so definitely needs close watching. Quality moisture will be in place from E AR into TN/MS by around 00z, spreading up into W KY by around 03z and wind profiles look just as favorable for long tracked, strong supercells. Obviously dont take STP too literally but I overlayed the rough position of the jet core at 500mb onto the STP map and that zone from NE AR into W KY and W TN certainly makes me nervous for a nocturnal intense tornado threat. Will need to see what kind of CAM signal develops for this area but already a fairly concerning look from the NAM.

1741812892712.png

All in all, a very significant one for Friday too. Some of the previous trends reducing the impact certainly seem to be slightly retreating but all I can think is thank god we had today's shortwave across the south otherwise we would have been in for an absolutely wild ride on Friday too. Could easily see the SPC going moderate as early as the first D2 outlook. Some aspects of the setup look reminiscent of some pretty high-end severe scenarios (northern mode especially has some hints of 12/15/21 and 3/31/23. Don't want to rush in completely at this point but if the current trends continue Friday-Saturday might unfortunately be one to remember.
 
FFC's afternoon update to their AFD mostly maintains messaging; potentially significant threat; also a call to action for people to begin to prepare for the threat as we approach the weekend.
.LONG TERM...
(Friday morning through next Tuesday)
Issued at 346 PM EDT Wed Mar 12 2025

Key Messages:

- Increasing likelihood of severe weather across North and Central
GA Saturday into Sunday, with all modes of severe modes on the table.

-Cooler and drier weather for early next week following an active
weekend. Frost may need to be monitored.

The primary forecast concern in the long term is the weekend severe
potential. Overall not much change with this latest forecast package
-- we are starting to get into the range of hi-res guidance for the
period in question which will help to further refine specific
details such as storm mode and timing. A few things that were noted
within latest hi-res guidance for Friday night into Saturday --
slightly more mass divergence aloft thus owing to a slightly
stronger LLJ at 850mb (60-70kts) and stronger surface winds ahead of
the system. With this forecast update, I did elect to bump up winds
on Saturday into early Sunday. Though winds do start to increase as
early as Friday in our western zones. This doesn`t change anything
from a messaging standpoint -- but further emphasizes the strong
dynamics that are in play. Long term guidance still has a decent
handle on the synoptic set up: 1- with an initial wave of energy
potentially bringing in some elevated convection/rain to parts of NW
GA Friday night into early Saturday and 2- a secondary wave of
energy bringing the entirety of the system eastward. All of this to
say still an impressive system and with notable consistency among
guidance this far. It will certainly be interesting to watch this
event unfold. For a well-thought out, detailed synoptic overview of
the weekend system please refer to the previous long term discussion.

It`s no surprise that there are still some uncertainties and
questions we are asking ourselves about the weekend system as we are
still several days out.

Elevated Convection/Rain Friday evening into Saturday: Does any of
this tap into the boundary layer? If so, with strong shear in place
and ML lapse rates ranging from 6-7 C/km, we may be looking at a
threat for hail and/or flooding in parts of northwest and/or west-
central GA with the first initial wave of energy.

There is also the question of if convection can get going in the
warm sector. Similar to the previous discussion, any amount of
instability that is available will contribute to convective
development especially with the amount of shear in play. Thus,
anything that were to get going ahead of the front may have
supercellular characteristics.

Finally, a PSA: Please start making and communicating your severe
weather plans now! Know where your safe place is, ensure your
weather radio is in working order, and consider your plans if they
involve being outdoors. With much of the action taking place
overnight (Saturday evening into Sunday morning) it is vital that
you remain weather aware. Be prepared not scared!
Click to expand...
 
You must log in or register to reply here.
Back
Top