Severe WX Southern Severe Weather Threat: 3/9-3/10

[CheeselandSkies]

It's early yet but based on the first sniff of the NAM, my virtual target would be west-central MS. Indices are slightly greater further W over AR, but I'm seeing some VBV issues in the soundings there. Instability issues further north. What an outbreak this system would be in late May with low-level instability overriding the warm front.

*Hodo looks decent to me in this sounding but the wind barbs, especially from 850 up to 700mb, look rather unidirectional with perhaps some very slight backing (although not as much as farther west), then only gradual veering as you go further up. That could be an issue despite the decent low-level turning.

 

[Kory]

It's early yet but based on the first sniff of the NAM, my virtual target would be west-central MS. Indices are slightly greater further W over AR, but I'm seeing some VBV issues in the soundings there. Instability issues further north. What an outbreak this system would be in late May with low-level instability overriding the warm front.

*Hodo looks decent to me in this sounding but the wind barbs, especially from 850 up to 700mb, look rather unidirectional with perhaps some very slight backing (although not as much as farther west), then only gradual veering as you go further up. That could be an issue despite the decent low-level turning.

The NAM looks nasty to me. My only concern is if we get an ongoing MCS across the Mid MS Valley into the Mid South, which may limit northward extent of CAPE. But overall, those kinematic parameters seem ominous.

 

[MetFromTheBlue]

I’m always skeptical of the NAM >60 hours out. That said, this morning’s NAM depicts a pretty intense severe weather event.

 

[WesL]

GREATLY appreciated folks. I was able to follow last weekend's event closely by bouncing between this site and Discord. It might be a cool idea to pool some reference websites under a pinned or labeled page to prevent someone like my partially derailing a thread's subject.

Now back to your thread subject.

Great idea. I think we can pull this off pretty easily. I'll see if I can put something together this evening.

 

[tennessee storm chaser]

12z nam coming in potent for Arkansas. Louisiana Mississippi....late Saturday ....

 

[NorthGaWeather]

12z nam coming in potent for Arkansas. Louisiana Mississippi....late Saturday ....

Even Western Alabama at the end of its run.

 

[rolltide_130]

The NAM looks nasty to me. My only concern is if we get an ongoing MCS across the Mid MS Valley into the Mid South, which may limit northward extent of CAPE. But overall, those kinematic parameters seem ominous.

There's quite the EML coming in on the 12z NAM. This may not be as big of an impact as the STJ really looks like its starting to get shunted out of this system. Still a ways to go but that was something I noticed..

 

[Richardjacks]

Seeing pds tor sounding trigger in east Miss on the nam. I just don't think we are going see the warm sector evolve like the nam is showing. First of all, the ground is quite chilled, once a southerly flow pulls in warmer air, there will be low clouds and fog...this could create some sort of 2ndry warm front and could be south of I20, but also could move north with enough sun on Saturday north of I20. Lots of details to figure out, I imagine the NAM is missing some of these.

 

[Kory]

Seeing pds tor sounding trigger in east Miss on the nam. I just don't think we are going see the warm sector evolve like the nam is showing. First of all, the ground is quite chilled, once a southerly flow pulls in warmer air, there will be low clouds and fog...this could create some sort of 2ndry warm front and could be south of I20, but also could move north with enough sun on Saturday north of I20. Lots of details to figure out, I imagine the NAM is missing some of these.

One would think the EML would allow mixing, thus mixing out any low clouds.

 

[Richardjacks]

One would think the EML would allow mixing, thus mixing out any low clouds.

yes, you would think so...not sure I remember where you have a strong eml as warm air is moving over a cold ground...will be interesting to see that transition.

 

[rolltide_130]

Seeing pds tor sounding trigger in east Miss on the nam. I just don't think we are going see the warm sector evolve like the nam is showing. First of all, the ground is quite chilled, once a southerly flow pulls in warmer air, there will be low clouds and fog...this could create some sort of 2ndry warm front and could be south of I20, but also could move north with enough sun on Saturday north of I20. Lots of details to figure out, I imagine the NAM is missing some of these.

One thing to remember is that, with strong enough return flow and temperatures, this can be offset. 11/29/16 started off CHILLY in the 40s with widespread fog in North AL. We didn't make it into the 60s until near sunset and then havoc ensued over North AL.

Also, we'll see 60s and 70s on Friday across a large amount of the region. It will be warming up ahead of Saturday as well.

 

[MetFromTheBlue]

Fog/stratus is a concern early season during rapid return flow, true. However, gulf opens up tonight into tomorrow/tomorrow eve. That’s 48-72 hours of return flow depending on where WRT the gulf you are. This shouldn’t be a problem.

Widespread convection N of a warm front is not anticipated w/this system as it was last week. Confidence in a widespread severe weather event is increasing.

 

[CAL]

Some of the projected kinematics with this event (i.e. flow trajectories, pre-frontal trough(s), relative vector orientations etc. etc.) are sure looking stout as of now.

 

[CheeselandSkies]

On 12Z NAM, hodos are looking very impressive over the AL/MS border region (moreso than further west where instability is greater). Could be another scenario to watch out for prefrontal initiation in that area (as with last Sunday) if it can destabilize.

Sounding attached is from a small pocket of higher CAPE depicted near and south of Columbus (ruh roh), MS.

 

[CAL]

With such a low amplitude trough/zonal upper jet configuration, I believe it's possible that the moisture return is in fact going to be stronger than currently forecast, resulting from the transverse jet circulation being oriented in such a way that the higher quality moisture advection is directly off the Gulf of Mexico (see Rose et al. 2004)

 

[Richardjacks]

With such a low amplitude trough/zonal upper jet configuration, I believe it's possible that the moisture return is in fact going to be stronger than currently forecast, resulting from the transverse jet circulation being oriented in such a way that the higher quality moisture advection is directly off the Gulf of Mexico (see Rose et al. 2004)

I wouldn't be surprised if the moisture return is stronger as you suggest, but I also believe there will be a transition period, especially in Alabama that may be play role in how far north and east the CAPE can spread.

 

[CheeselandSkies]

It's a quite different setup synoptically, but this is already giving me vibes of last Sunday in the sense that there are caveats apparent but also clearly the potential for something nasty to happen. SPC and other forecasters will once again need to strike a balance between sounding too bullish, since it's not (at this point) a high-risk outbreak scenario, while emphasizing that everyone in the threatened area should have a way to receive warnings on Saturday and a plan for what actions to take should they do so.

 

[tennessee storm chaser]

It's a quite different setup synoptically, but this is already giving me vibes of last Sunday in the sense that there are caveats apparent but also clearly the potential for something nasty to happen. SPC and other forecasters will once again need to strike a balance between sounding too bullish, since it's not (at this point) a high-risk outbreak scenario, while emphasizing that everyone in the threatened area should have a way to receive warnings on Saturday and a plan for what actions to take should they do so.

I can see a area puit in moderate risk by Saturday morning .... especially nam verifies

 

[amp1998]

I can see a area puit in moderate risk by Saturday morning .... especially nam verifies

And I can see an ENH risk for Day 3 coming for Arkansas, Tennessee, and Mississippi.

 

[TornadoFan]

Looks like the 00Z NAM shifted the threat further west into Texas and southern Oklahoma. And I think I can see a bit of VBV on the soundings.