Severe WX Severe Threat 17-18 March 2021

[MattW]

Uh so this is what the NAM is saying for 10 miles NE of Tuscaloosa at 01:00 CDT Thursday morning...

 

[Equus]

And there's our uptrend after the three-day-out downtrend. Buckets of yikes. Gonna be paying very close attention to this one.

 

[CheeselandSkies]

Uh so this is what the NAM is saying for 10 miles NE of Tuscaloosa at 01:00 CDT Thursday morning...

...and that's not even close to the most impressive hodograph available on forecast soundings across the region.

* Also valid time of 03Z is 10:00 PM CDT.

 

[warneagle]

The most impressive hodographs I've seen are over central Alabama in the 10 pm to 1 am timeframe, which is not great! Even if the NAM is overcooking the instability (the GFS is in the 650-750 J/kg range while the NAM is double that in some places) there would be sigtor potential well into the overnight hours.

 

[Clancy]

The most impressive hodographs I've seen are over central Alabama in the 10 pm to 1 am timeframe, which is not great! Even if the NAM is overcooking the instability there would be sigtor potential well into the overnight hours.

SPC's D3 discussion also suggests tornado threat would definitely persist past dusk.

 

[Fred Gossage]

The most impressive hodographs I've seen are over central Alabama in the 10 pm to 1 am timeframe, which is not great! Even if the NAM is overcooking the instability (the GFS is in the 650-750 J/kg range while the NAM is double that in some places) there would be sigtor potential well into the overnight hours.

The GFS is decoupling the boundary layer, magically, at sunset. It's done this since before it was called the GFS. We have mid/upper 60 dewpoints, skies will be mostly cloudy or becoming overcast by then, and strengthening boundary layer winds. It goes against this planet's physics to do that.

 

[Fred Gossage]

12z NAM is even stronger with the 850mb jet. We're now talking about a 67 to almost 70 kt max and a much bigger area of 60+ evening and overnight. It's also trending stronger with the 850mb winds during peak heating as well.

 

[Mike S]

I hate for my first post here to be an "in my backyard" question, but what about ~40 miles east of ATL?

Welcome to TalkWeather!

 

[Fred Gossage]

The RGEM, the consistently least bullish model for days and overall with systems in general, has a 65 kt 850mb jet after dark. This is locking in...

 

[Equus]

The HRW CAMs will come into range later today, will be interesting to see.

 

[Fred Gossage]

The HRW CAMs will come into range later today, will be interesting to see.

And the ARW is already dead quiet on the warm front through 12z Wed, closer to the NAM suite and RGEM than the HRRR.

 

[KevinH]

The SPC put the D3 MOD risk JUST outside of the west of me, in Columbus, GA. I know not to get too caught up in the categories, but I am hoping things to not trend worse for West Central GA.

Thoughts anyone?

 

[Fred Gossage]

The SPC put the D3 MOD risk JUST outside of the west of me, in Columbus, GA. I know not to get too caught up in the categories, but I am hoping things to not trend worse for West Central GA.

Thoughts anyone?

Not correcting to be a jerk, but to make sure you know it's not currently higher than what it is... but *ENH.

You need to be vigilantly watching this one. The low-level winds overnight are still trending stronger, and the magnitude of this whole ordeal is still in flux (but while in flux, not backing off). I still think the worst is west/northwest of you, but you need to be vigilant.

 

[KevinH]

Not correcting to be a jerk, but to make sure you know it's not currently higher than what it is... but *ENH.

You need to be vigilantly watching this one. The low-level winds overnight are still trending stronger, and the magnitude of this whole ordeal is still in flux (but while in flux, not backing off). I still think the worst is west/northwest of you, but you need to be vigilant.

Oops! Yes, EHN sorry.

Hopefully things STAY at the ENH level, but even ENH is still something to watch.... CLOSELY.

And I will be up all night Wednesday watching this with my Wx radios charged, RadarScope on my phone, Twitter on my iPad, and my laptop on several weather pages (including IEMBot).

Thanks again Fred!

 

[Richardjacks]

There are many reasons to be concerned but the one thing that stands out to me besides the instability is the shear, more importantly the low level turning and how the low level winds are backed over a large space, and the amount of time they are backed...all under very strong low level jet. Those soundings are very impressive.

 

[Fred Gossage]

There are many reasons to be concerned but the one thing that stands out to me besides the instability is the shear, more importantly the low level turning and how the low level winds are backed over a large space, and the amount of time they are backed. Those soundings are very impressive.

Without worry of advecting in a more stable air mass while being as backed as they are.

 

[Richardjacks]

Without worry of advecting in a more stable air mass while being as backed as they are.

That's true...usually low level winds aren't that backed for that long period of time anyway.

 

[Bamamuscle]

Lotta red and purple on this map.. Anything over 1 is sufficient for tornadoes right?


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[warneagle]

I've noticed that 05/04/03 is popping up as an analog on a lot of the NAM soundings...

 

[Equus]

The parameter space for this is ominous. Usually we get a fairly narrow corridor of favorable conditions but looks like this could be a longer duration event.