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

Equus said:
It looks like only seven other threads on the entire weather portion of the site after its 2017 revival have hit this many replies, and we're still two days off; going to make a run for the top tier
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Top-tier as in the forbidden day that shall no be named?
 
maboyes said:
:/.Hello all, I am new to East Tennessee but not new to weather watching. My dad used to fly reconnaissance out of Belle Chasse LA. Been through a few hurricanes and tornadoes. Used to watch the water spouts from Lake Pontchartrain when there was an amusement park there! Watching this current systems of severe storms. My husband is not taking this very seriously, at least not as seriously as I am. Looks like east TN/Knoxville area so far is not in a bulls eye, but still pretty severe weather/thunderstorms. Am I over worried?
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East Tennessee is in the slight risk area, so it certainly bears watching.

This is from the Day 3 Convective Outlook discussion that was posted overnight and will be updated again in the next 20 minutes or so.

"
Additional convection is expected to develop along an
eastward-advancing cold front during the afternoon and into the
overnight. An organized line of storms will pose a risk for damaging
wind swaths and tornadoes across northern MS/AL into TN, eastward
into GA and the western Carolinas overnight. "


You can click here to see the new discussion when it drops at 2:30pm - https://www.spc.noaa.gov/products/outlook/day3otlk.html

This link lists all the updates - https://www.spc.noaa.gov/products/outlook/
 
keithGA said:
AFD from FFC




.LONG TERM...
(Saturday morning through next Wednesday)
Issued at 253 PM EDT Thu Mar 13 2025

Key Messages:

- Severe weather is expected across North and Central Georgia
Saturday evening into Sunday. All modes of severe weather are
possible: damaging winds, tornadoes, and severe hail. A
significant tornado (EF-2 or greater) is also possible.

- Forecast rainfall amounts for Friday Night through Sunday
range between 2-3" across North Georgia and 1-2" elsewhere. A
Slight Risk (Level 2 out of 4) for flash flooding exists for
North Georgia during this timeframe.

Forecast:

A very strong storm system will bring severe storms to much of the
Southeast between Friday night and Sunday afternoon. We have
consistently seen a notable signal for a strong wind component
through the atmospheric column as well as energy (fuel) -- thus, the
overlap of these two supports the threat for severe weather for us
in North and Central Georgia. Timing primarily lies between Saturday
evening through Sunday afternoon with that threat moving from west
to east as the front pushes the line of storms through the state.

As a general overview, at the start of the long term (Saturday
morning), there could be some rain and storms ongoing and/or
diminishing across parts of Northwest Georgia. The Marginal Risk
area (Level 1 out of 5) as painted by SPC, is to account for any
severe thunderstorms that are able to maintain themselves as they
enter into our northwest zones early Saturday morning in response to
the initial wave of energy swinging through the TN Valley.
Damaging winds look to be the primary threat with any severe
thunderstorms that move through northwest Georgia early Saturday
morning.

Moving into the day on Saturday, a strengthening upper low will be
forced eastward as a second piece of energy rotates around the base
of the broader upper trough. At the surface, a cold front will be
tracking eastward across the ArkLaMiss towards the TN Valley. This
will result in notable height falls, a strengthening LLJ (60+ kts),
and allow for ample moisture to stream into the region bringing up
our dewpoints from south to north during the day. Thunderstorms
accompanying a cold front will move through Saturday night into
Sunday afternoon. Storms look to finally clear our southeast zones
by Sunday evening. As we are becoming more into the range of some of
the higher resolution model guidance there are a few things to note:

1- there are some 'weakening' trends with the line of storms as it
moves eastward through our area overnight Saturday into Sunday.
However, all severe threats will still be in play across all of our
forecast area so don't let your guard down! The wind energy and
other ingredients that have been noted with this system will still
be present. As we know nocturnal severe events are especially
hazardous -- so please make sure you have appropriate weather safety
plans in place.

2- overall timing of when we can expect severe weather to move
through the state continues to be refined. Some hi-res guidance has
storms moving into northwest and west-central Georgia as early as 6-
8PM Saturday. However, current thinking is still a little later 8-
10PM at the earliest.

3- a prior uncertainty was if ongoing convection Friday into
Saturday morning would contaminate the environment heading into
Saturday. At least for now this does not appear to be the case. But
we are keeping that possibility in the back of our minds. Adding on
to the previous point, there is a possibility that some portions of
our area (southwest, west-central GA) clear out mid-morning
Saturday. If that's the case the atmosphere would have some time to
recover as moisture continues to stream into the state.

At this time SPC maintains an Enhanced Risk (Level 3 out of 5) for
areas roughly along and west of a line from Athens to Macon down to
Americus. Also within this Enhanced Area is a hatched area
indicating a greater probability of significant severe weather
occurring (i.e. large hail, significant damaging winds, and strong
tornadoes). In addition to severe hazards, the flooding threat
overnight Saturday into Sunday remains. With this forecast update,
forecast storm total rainfall for the duration of this event from
Friday overnight through Sunday is largely unchanged. Totals for
North Georgia range from 2-3" with 1-2" elsewhere. The time window
for the highest flood threat is late Saturday evening to Sunday
morning. These totals are fairly modest, though any training of
thunderstorms over a specific area and multiple rounds of rainfall
throughout the weekend could result in minor flash flooding and/or
local river flood concerns. WPC maintains a Slight Risk (Level 2 out
of 4) for North Georgia on Saturday.

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!
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Imagine seeing this RIGHT after you posted it thinking it was @Clancy, and then realizing you posted the AFD in the wrong thread lol

@Clancy we aren’t going to play your cat and mouse games when these outlooks, watches, and warnings are issued for Saturday’s OK!? LOL

(Side note: yes we are ROFL!!!)
 
Grand Poo Bah said:
So is the STP in the HRRR broken or what? Looks like it also produced a 19 in Oklahoma with the March 3rd event.

View attachment 35316

That combined with multiple 25 STP days it produced last year tells me it's putting a decimal in the wrong place or weighing something too heavily. Hard for people to take the numbers the NAM is pumping out seriously when it can immediately be shrugged off as just another over hyped day because of what the HRRR is producing.
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It's pretty common for the CAMS like the HRRR to model very high STP values after dark in the plains, especially as we head further into the season. This is because the while plains often have sufficient instability for severe storms, the LLJ will ramp up after dark and massively increase the low level shear. Large low level shear combined with instability will lead to very high values of STP. However the nocturnal plains LLJ specifically is accompanied by a very marked increase in capping (CIN) and so you essentially never get storms actually forming in this environment.


This is not the case for Dixie, especially this event. The peak parameter space will coincide with a trough and warm sector encouraging discrete or semi-discrete convection. Obviously STP is a composite parameter and doesn't reflect the real tornado risk - but in a case like Saturday it can be slightly more applicable and the tornado threat really should be taken seriously.
 
UK_EF4 said:
It's pretty common for the CAMS like the HRRR to model very high STP values after dark in the plains, especially as we head further into the season. This is because the while plains often have sufficient instability for severe storms, the LLJ will ramp up after dark and massively increase the low level shear. Large low level shear combined with instability will lead to very high values of STP. However the nocturnal plains LLJ specifically is accompanied by a very marked increase in capping (CIN) and so you essentially never get storms actually forming in this environment.


This is not the case for Dixie, especially this event. The peak parameter space will coincide with a trough and warm sector encouraging discrete or semi-discrete convection. Obviously STP is a composite parameter and doesn't reflect the real tornado risk - but in a case like Saturday it can be slightly more applicable and the tornado threat really should be taken seriously.
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Always enjoy your posts. What's your general read on things, being across the pond and away from the risk area?
 
Call it a feeling but if we are starting the severe weather season with this, this gives me a bad feeling for April and May (But April especially)

This is just a feeling I have, but we will have to see how the rest of March pans out to get an idea of what April hold in store for us.
 
Atlantic said:
Call it a feeling but if we are starting the severe weather season with this, this gives me a bad feeling for April and May (But April especially)

This is just a feeling I have, but we will have to see how the rest of March pans out to get an idea of what April hold in store for us.
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@Fred Gossage and another MET have already spoken about this season so the feeling you have is warranted.
 
Clancy said:
Always enjoy your posts. What's your general read on things, being across the pond and away from the risk area?
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Thank you, and likewise!

I think same as many others, concerned for both Friday and Saturday.

Friday I am definitely eyeing up the corridor from E MO into S IL as well as a little south into KY and TN for a strong tornado threat - the southern edge of the jet core will interact with the northern edge of the instability plume, potentially producing a couple long tracked discrete or semi-discrete supercells. For Saturday, I think everyone can agree pretty much anywhere from E MS into C AL looks pretty high-end.
 
UK_EF4 said:
It's pretty common for the CAMS like the HRRR to model very high STP values after dark in the plains, especially as we head further into the season. This is because the while plains often have sufficient instability for severe storms, the LLJ will ramp up after dark and massively increase the low level shear. Large low level shear combined with instability will lead to very high values of STP. However the nocturnal plains LLJ specifically is accompanied by a very marked increase in capping (CIN) and so you essentially never get storms actually forming in this environment.


This is not the case for Dixie, especially this event. The peak parameter space will coincide with a trough and warm sector encouraging discrete or semi-discrete convection. Obviously STP is a composite parameter and doesn't reflect the real tornado risk - but in a case like Saturday it can be slightly more applicable and the tornado threat really should be taken seriously.
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Extremely interesting you'd point this out because almost all the times the HRRR has gone off the charts with STP, it has coincided with "busts". I vividly remember being shocked when it got all the way up to 42 on May 6th 2024, and as we watched the event play out live, massive non tornadic supercells floated over the main area of concern and did nothing. I remember it almost felt eerie and I had a profound curiosity about what was holding them back. It wasn't until several hours later that tornadoes finally started dropping and Barnsdale was hit with a powerful EF4. That was the start of a 5 day outbreak that produced 185 tornadoes.

Same thing happened this year with the underperforming March 3rd system that had an HRRR STP of 15. Except it never really dropped any tornadoes.
 
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