Severe WX April 11th-13th, 2020 Severe Weather Threat

[MichelleH]

Everybody pray.

 

[Equus]

00z NAM is in and really I'm going to run out of superlatives before tomorrow evening. Steep lapse rates/hint of an EML, horrifying hodographs from the depths of madness. 65+ dews up to Nashville. Still want to wait til Saturday or so to ensure that everything continues to line up to bring these scary scenarios to life, but it certainly has the look of a higher end day...

Not that composites are among the more important parameters to look at, but here's every single Alabama county STP 2+



Whatever we did to hurt the NAM's feelings, we're sorry, I swear

 

[Kory]

Big ole 90 contour. But...look at the eastward extend of that. This is going to be a wide warm sector...

 

[Equus]

Nearly the entirety of 7 states potentially at play. Gonna be a long day

 

[tennessee storm chaser]

Big ole 90 contour. But...look at the eastward extend of that. This is going to be a wide warm sector...

View attachment 2723

Appears the north trend continues ... parts Tennessee may be dealing with this now

 

[brianc33710]

What does the new NAM say? During hurricane season I'll stay up all night for each NAM & GFS update. I would rather just hold out until Friday AM unless it's something huge.

 

[Brice]

Appears the north trend continues ... parts Tennessee may be dealing with this now

Let's not have a Cookeville 2.0 or any EF4 for that matter

 

[Brice]

The low level winds are concerning, they are screaming from the GOM south to north. Also, the mid level winds are pretty strong in Mississippi.

 

[andyhb]

Will have more thoughts on this later as we get closer, but IMO this is, as it sits, quite easily the most threatening setup across the SE that has presented itself since 2011.

I’m not sure I can ever recall a March/April setup with this many global models showing such extreme shear overlapping appreciable instability. There are still caveats present mostly concerning early convection, cloud cover, and lapse rates, but with such a wide region of deep boundary layer moisture, I can’t imagine that at least somewhere from TX to the Carolinas is going to see a significant problem.

 

[cincywx]

day 3 moderate


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[Equus]

So uh... D3 Moderate

 

[xJownage]

Mentions strong tornadoes in the warm sector with long-track supercells evolving out of the morning convection. Seems like there could possibly be a second wave as well with this system. Scary stuff.

 

[KoD]

Seems very justified imo. It's quite a large region as well, I wonder if that's due to uncertainty on where the highest area will be, or that the risk area is expect to be that large - I assume it's a bit of both.

 

[tennessee storm chaser]

Seems very justified imo. It's quite a large region as well, I wonder if that's due to uncertainty on where the highest area will be, or that the risk area is expect to be that large - I assume it's a bit of both.

Wow. Day 3 enhanced also from Memphis to Nashville now I was expecting north trend. Bu this much? Moderate just barely south that

 

[Isaac Williams]

This is an excellent first, more focused outlook. It encapsulates the most favorable parameter spacing for the most significant risk, but it also just shows how much AREA this event will cover.

 

[Kory]

NWS Birmingham is a 5/5 on the tornado threat Sunday.

 

[Kory]

We're now seeing this get into the larger range CAMs. It is as ugly as we have seen...

3km showing an unabated warm sector surging north with dews 70+ and highs near 80...in Western AL.

 

[Bama Ravens]

So we are looking at one of the most dangerous setups we’ve seen since 2011, during a massive global pandemic?

 

[Kory]

So we are looking at one of the most dangerous setups we’ve seen since 2011, during a massive global pandemic?

I would say so. This is textbook jet structure for getting long-lasting rotating updrafts.

I suspect we'll have a radar that looks similar with confluence bands of supercells out ahead of a broken line of convection along the dryline.

 

[Kory]

There was some veer-backing on some of the forecast soundings at the far end of the 3km NAM's range, but I'm kind of grasping at straws looking for potential mitigating factors at this point because there aren't any big, obvious ones.

As you get closer to the dryline...that seems more likely. But I could see this having confluence bands of supercells well out ahead in the warm sector that are dropping tornadoes, while you have a broken line along the boundary well west producing SVR warnings. Similar to 4/27...all the big tornadoes were out ahead and the dryline was mostly sub-severe with a SVR warning or two.