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

Kory said:
Yeah, we’re not going to come close to the instability profiles of that day.
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Indeed, this might be more along the lines of 4/8/98 or 4/15/11 or the like (perhaps once a decade or so) than a super outbreak like 4/3/74 or 4/27/11.
 
I think of the Illinois PDS forecast last month. A couple of variables changed the morning of (Day 1) & the whole forecast went off the rails. At least for the Illinois portion of the forecast. It was supposed to be the outbreak of the decade according to more than a few. I realize the dynamics for this Sunday are a different animal compared to that event but small scale features can play a major role in Day 1 reality.
 
bwalk said:
I think of the Illinois PDS forecast last month. A couple of variables changed the morning of (Day 1) & the whole forecast went off the rails. At least for the Illinois portion of the forecast. It was supposed to be the outbreak of the decade according to more than a few. I realize the dynamics for this Sunday are a different animal compared to that event but small scale features can play a major role in Day 1 reality.
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There was definitely some wavering the day prior by the Euro (wind fields were funky) and then we had the morning blob of convection. Something to keep an eye on here (not those two things specifically, but wavering by models in general). I think the door has closed for major synoptic changes at this point, but some smaller-scale stuff needs to be ironed out. Like any severe weather forecast here.
 
Kory said:
It’s also interesting to see some of the people who clearly have less knowledge of Dixie Alley (not a knock on them) assert a little band of convection like that will inhibit advection of an unstable airmass from a very close Gulf of Mexico. Even used the Illinois example. Only thing is Illinois doesn’t have a large water body adjacent to it...one with well above average water temperatures. Dixie does...
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I agree with you. I can’t see the tweets because I’m blocked by that guy (I’ve never even heard of him, much less tweeted at him in anger), so I can’t read the thread, but AJ was wondering if there is any discussion of moisture quality. This is definitely not a situation where moisture and temps are in place for days. Could this be an inhibiting factor?
 
To be fair, the lack of instability compared to other huge outbreaks isn't going to make a huge difference here. This maybe not being 4/27 doesn't mean it doesn't have the potential to be a very devastating outbreak, and the possibility of multiple waves of supercells makes 4/27 a somewhat valid, if not loose, comparison. If the soundings from the warm sector after the first wave hold true, storms could fire almost anywhere in the warm sector, basically at will.

That being said, comparing any day to a super outbreak 2 days in advance is irresponsible at best and harmful at worst (in the case it busts).
 
gangstonc said:
I agree with you. I can’t see the tweets because I’m blocked by that guy (I’ve never even heard of him, much less tweeted at him in anger), so I can’t read the thread, but AJ was wondering if there is any discussion of moisture quality. This is definitely not a situation where moisture and temps are in place for days. Could this be an inhibiting factor?
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Potentially on the northern fringes of the risk area, yes I think so. But as we saw with January 11th, we went from lows in the 30s with dews near 30 two days prior to the event, but with wicked low-level flow the night before/day of, it allowed us to reach the 70s in South/Central AL by late morning. This is now 3 months later into the spring season and with just as strong low-level flow...I'm not as concerned that moisture return will be a problem for MS/AL/West-Central TN.
 
What makes 4/27 stand out so bad is how perfectly spaced the supercells were, could always get storms firing too close or otherwise destructively interfering but that won't come close to outright killing the risk
 
Equus said:
What makes 4/27 stand out so bad is how perfectly spaced the supercells were, could always get storms firing too close or otherwise destructively interfering but that won't come close to outright killing the risk
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This. There's still so many details that need to be ironed out before we can even confirm there will be a serious outbreak at all.
 
Also on the realm of something besides this, what's going on tomorrow? Several of the shorter range models have supercells firing in oklahoma during the day in a very impressive environment, and the cap looks strong enough to keep storms from firing on the current model runs in central Texas. For all of you who are more experienced, thoughts on saturday?
 
xJownage said:
Also on the realm of something besides this, what's going on tomorrow? Several of the shorter range models have supercells firing in oklahoma during the day in a very impressive environment, and the cap looks strong enough to keep storms from firing on the current model runs in central Texas. For all of you who are more experienced, thoughts on saturday?
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Looks like dry line action that grows upscale into a complex. Pretty weak flow aloft.
 
Im not sure what model js was using but the helicity updrafts were down right stout going through NW Al. Seemed to be heavily concentrated West of 65 and N of Ttown. Ive seen several models with insanely high stp numbers 8/9 in this area as well. We still have a long way to go but thats becoming a narrowed area of interest for me. Also i agree with others on here that there are still issues that could arise that could lessen this threat. Ive seen it happen too many times in my life time.
 
Definitely concerned about my area if everything lines up like many models are showing, could be the corridor to watch
 
xJownage said:
Also on the realm of something besides this, what's going on tomorrow? Several of the shorter range models have supercells firing in oklahoma during the day in a very impressive environment, and the cap looks strong enough to keep storms from firing on the current model runs in central Texas. For all of you who are more experienced, thoughts on saturday?
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This is what I've been monitoring a bit more today. Things look pretty quiet in N-TX/OK until tomorrow afternoon when there's some spotty storm activity. The thing I'm growing concerned with is that I'm starting to see much higher STP values overnight that have just started coming in on the HRRR that were not there this morning.

This is a sounding around Garland/Richardson line slightly NE of Dallas at 10 PM Saturday. Around the same time frame, I'm seeing STPs in the 6s and 7s in far SW Texas.

lm0Hk9P.png

The activity is not super widespread all things considered, but there's a decent cluster of cells in the DFW Metroplex during that time frame that appear to be more tornadic in nature.
 
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darkskys25 said:
Im not sure what model js was using but the helicity updrafts were down right stout going through NW Al. Seemed to be heavily concentrated West of 65 and N of Ttown. Ive seen several models with insanely high stp numbers 8/9 in this area as well. We still have a long way to go but thats becoming a narrowed area of interest for me. Also i agree with others on here that there are still issues that could arise that could lessen this threat. Ive seen it happen too many times in my life time.
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I believe it was Baron's model
 
Yeah that was the Baron model. I'd like to say it's a little on the excessive side but best to prepare for the worst just in case.
 
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