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Severe WX Severe Threat 17-18 March 2021

Equus said:
05z HRRR doesn't look like a fun ride

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I wish I was exaggerating but that shows 4 seperate supercells passing right through the exact tiny corner of Jefferson that I live in. And, amazingly, each time it's the hook itself that is cutting through.

Hard pass on this run.
 
sak said:
looking at the hrrr for trends is fine but it’s not very useful in predicting down to the part of a county that is going to get hit.
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Trust me, I understand the function of CAM models. It was merely an observation not a forecast.

Nonetheless, the HRRR has absolutely nailed the general placement of key supercells during an outbreak on more than one occasion. It's also useful for backtesting to actual radar trends that see how closely an event is unfolding compared to how it was modeled.

The HRRR is but one tool. But, when it is consistently portraying a specific threat for multiple runs before an event begins, you ignore it at your own peril. The fact that the HRRR is showing multiple completely discrete supercells barging through Jefferson County is extremely concerning to me. Placement may be off in the event itself, but if the HRRR is properly resolving storm mode then we're on the cusp of a high-end event for large swathes of MS/AL.
 
The CAD is coming in a bit stronger on the 06Z HRRR, hence a slower, more southerly warm front by 20Z.

Otherwise, the general upward trend toward a more volatile environment and storm mode continues.
 
Speaking of the HRRR, the 06z run is the stuff nightmares are made of. There's no downtrending taking place -- only the converse. Storm mode looks about the best it has looked thus far. Instability and shear are deeper/higher. Lapse rates look more than acceptable. SRH is outright scary in certain places.

The ceiling on this event is astronomically high.
 
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07Z HRRR showing long-tracked supercells well into western TN. This run looks like a full-scale violent outbreak in MS/AL/W TN/E AR.

The crossovers on this run, combined with instability and low-level dynamics, are absolutely the most robust seen on the HRRR thus far.
 
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Fred Gossage said:
Don't be surprised if the High Risk is expanded farther across north central Alabama in coming outlooks. High resolution guidance continues to trend more ominously for north and central Alabama as early as mid afternoon with the open warm sector stuff. This may extend as far north as far southern middle TN.
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Current trends answer in the affirmative thus far.
 
CheeselandSkies said:
Welp, there was the CAM (especially HRRR) uptrend I was waiting for to get to high-risk level confidence.
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The 08z HRRR is nuts. Supercell fiesta.

Going to be interesting to see if the supercell it develops around 18z in Walker County moving into Cullman verifies and if that's where the party starts. Very reminiscent of some previous outbreaks.
 
Fred Gossage said:
Rich Thompson is on the 13z Day 1 outlook today. He is the best of the best there, along with Roger Edwards. If there is a need for expansion, and I've stated my case about that, then I have confidence he will do whatever is necessary.
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What's your current thinking if they expand? To the east a good bit and also potentially further south?
 
Evan said:
What's your current thinking if they expand? To the east a good bit and also potentially further south?
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I think it needs to come on over across much of the northern half to 2/3 of Alabama and maybe into the first row of southern TN counties along the MS line and the AL line, especially from Giles westward.
 
Fred Gossage said:
Man, each HRRR run has a greater and greater number of violent level UH tracks from discrete or semi-discrete storms...
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Weekend warrior question here Fred, and good morning. At this stage, which I guess is basically “go-time”, should we really be leaning into the CAMS more than other models? Also, it seems to me that these UH tracks seem to always be pretty dang accurate, do you think that most meteorologists stay away from using them for fear of people taking the tracks too literally?


Sent from my iPhone using Tapatalk
 
CheeselandSkies said:
Latest HRRR now hammers Alabama throughout the afternoon with nothing really happening in the current high risk area over MS until 00Z or later. Good call, @Fred Gossage .
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Yep, there has been a consistent signal for some supercells to develop along what I would think are confluence bands in southern MS/AL and lift NE as deep layer and low-level shear both increase through the afternoon. Discrete convection way ahead in the warm sector with supercells back along the boundary. What an ugly look.
 
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