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Severe Weather 4/17/26

slenker said:
400+ SRH combined with 4000+ J/kg of CAPE isn’t an extreme environment? In April? Dude, what? The soundings from every day you just mentioned are extreme, don’t get me wrong, but they didn’t check both boxes like this one does. Like I said, there have been environments with these parameters in place, but they didn’t have supercellular convection moving through them, or they had bad storm modes. This is an intense environment.

There’s still plenty of time for this to downtrend, and we want that for sure. Don’t downplay this modeled environment until we see good reason to do so.
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It's an extreme environment but it's not like we don't have environments modeled like this a couple times a year. It's certainly not one of the two worst modeled environments since 5/20/19.
 
N0mz said:
It's an extreme environment but it's not like we don't have environments modeled like this a couple times a year. It's certainly not one of the two worst modeled environments since 5/20/19.
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I respectfully ask you to provide examples of environments within the last 5 years that had 4000+ cape, 400+ helicity values, mllr above 8c/km, favorable vertical wind shear vectors, in a minimally capped parameter space all at the same time, because Im curious.
 
jiharris0220 said:
I respectfully ask you to provide examples of environments within the last 5 years that had 4000+ cape, 400+ helicity values, mllr above 8c/km, in a minimally capped parameter space all at the same time, because Im curious.
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6/20/25, 5/18/25, 5/4/24, 4/26/24, just from the last two years.
 
N0mz said:
6/20/25, 5/18/25, 5/4/24, 4/26/24, just from the last two years.
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None of these dates had correspondingly 4000+ cape with 400+ SRH and 8+c/km laspe rates.
These dates had higher shear values, but lacked the extreme laspe rates and sb cape values to go with those high shear numbers.
And I’m straight up not sure where you’re finding corresponding values that high in 4/26/24.
More importantly, none of these dates are as early or up north as Fridays threat will be. Although that’s besides the point.
 
jiharris0220 said:
None of these dates had correspondingly 4000+ cape with 400+ SRH and 8+c/km laspe rates.
6/20/25 and 5/18/25 had higher shear values, but lacked the extreme laspe rates and sb cape values exceeding that number with those higher shear values.
And I’m straight up not sure where you’re finding corresponding values that high in 5/4/24 and 4/26/24.
More importantly, none of these dates are as early or up north as Fridays threat will be. Although that’s besides the point.
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5/19/25 (KS): 3k cape and 600 esrh, just as bad or worse:
https://app.chasearchive.com/case/69386fb6180f2854f1521d1e4bc5a150

5/19/25 (OK): 5k cape and 600 esrh
https://app.chasearchive.com/case/382f7bcde615fe27cbe3029482e484e8

5/25/25: 4k cape and 370 esrh
https://app.chasearchive.com/case/e5ffa7209b992471e225fb4c21dd5ade

5/26/24: 4k cape and 450 esrh
https://app.chasearchive.com/case/ed6df5e969c7494bab61aab584dd351f
 
N0mz said:
5/19/25 (KS): 3k cape and 600 esrh, just as bad or worse:
https://app.chasearchive.com/case/69386fb6180f2854f1521d1e4bc5a150

5/19/25 (OK): 5k cape and 600 esrh
https://app.chasearchive.com/case/382f7bcde615fe27cbe3029482e484e8

5/25/25: 4k cape and 370 esrh
https://app.chasearchive.com/case/e5ffa7209b992471e225fb4c21dd5ade

5/26/24: 4k cape and 450 esrh
https://app.chasearchive.com/case/ed6df5e969c7494bab61aab584dd351f
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You know what? Fair. I stand corrected when it comes to the straight numbers in terms of CAPE and SRH.

I will say, though, that these soundings aren’t as impressive from the standpoint of streamwise vorticity combined with lapse rates. This is my last post regarding this, don’t want to clog the thread with something off-topic.
 
N0mz said:
5/19/25 (KS): 3k cape and 600 esrh, just as bad or worse:
https://app.chasearchive.com/case/69386fb6180f2854f1521d1e4bc5a150

5/19/25 (OK): 5k cape and 600 esrh
https://app.chasearchive.com/case/382f7bcde615fe27cbe3029482e484e8

5/25/25: 4k cape and 370 esrh
https://app.chasearchive.com/case/e5ffa7209b992471e225fb4c21dd5ade

5/26/24: 4k cape and 450 esrh
https://app.chasearchive.com/case/ed6df5e969c7494bab61aab584dd351f
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I admittedly forgot 5/25/25 had 8+c km laspe rates. So I’ll retract my statement for that day.
But none of the other soundings here have all three correspondingly high parameters. Which I think is the misunderstanding here.
Obviously we get multiple days every year where cape is well above 4000, SRH is above 400, and MLLR above 8c/km.
But the point of my comment was that we haven’t had any events (except for 5/25/25, my bad) that had all three parameters corresponding with one another.
On days like this you can have 5000+ cape and SRH values above 500 and LLLR at 9c/km, but they aren’t aligned.
And looking back at the soundings of May 20th, 2019, I actually can’t find any soundings above 4000+ cape that had the other one of two parameters that high, so I guess my original statement wasn’t exactly correct.
 
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slenker said:
You know what? Fair. I stand corrected when it comes to the straight numbers in terms of CAPE and SRH.

I will say, though, that these soundings aren’t as impressive from the standpoint of streamwise vorticity combined with lapse rates. This is my last post regarding this, don’t want to clog the thread with something off-topic.
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Still not sure I understand how very extreme sounding examples show how Friday's soundings "aren't that extreme", but alas. It's been an extreme last few years.
 
I unfortunately don't have a lot of time to dig into it, but I think what's being missed with the OK/KS/MO part of the threat is potential for the development of the secondary low. If one does form, but it's down in the TX panhandle like many global models are showing, then it won't do much for the tornado threat. Place it further northeast into central/south-central KS, and the threat gets a lot more interesting w/ the environment being modeled.
 
N0mz said:
ENH kept
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Did you see the massive expansion north into WI? Also, check out this statement in the forecast discussion-

A corridor of perhaps greater tornado risk/coverage may develop near the surface low from northeast IA into central WI. Low-level SRH will be maximized in this area and forecast soundings indicate large, curved hodographs becoming elongated above 2-3 km. Furthermore, mixing ratios near 14 g/kg and very steep lapse rates should support robust updrafts with low cloud bases. This are may become a focused corridor for stronger tornadoes.
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I think we could see a moderate risk as soon as the next update.
 
Taylor Campbell said:
Did you see the massive expansion north into WI? Also, check out this statement in the forecast discussion-



I think we could see a moderate risk as soon as the next update.
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I think they'll do it at 1630 for wind, which just needs to be bumped from 45# to 60# for MDT. I think a tornado-driven MDT is also likely, but I wouldn't have enough confidence to do it on D2.
 
Taylor Campbell said:
Friday is going to be downright nasty and very destructive. Is @CheeselandSkies going to be back home to chase this?
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Yup. Got home Monday evening after seeing the tornado near Truman, MN. Chased Tuesday although didn't see much, too many cell interactions and HP modes. Actually got caught in the RFD of the tornado-warned cell near Dodgeville and the slick roads combined with a gust of wind caused me to slide out and clip a guardrail leaving a scratch all along the passenger side of my vehicle. Fortunately no worse than that. Long-time Wisconsin chaser Scott Weberpal got the tornado near Briggsville which as far as I can tell was the only one in Wisconsin that was actually visible and photogenic.
 
The 06z HRRR portrays a dangerous scenario for WI. Basically a line of semi-discrete supercells as well as a few discrete cells in a well sheared and very unstable environment. IA/IL gets in on the fun too with a few supercells and a cluster of them as well. with If this trend continues, I would not be shocked for an increase in tornado probabilities the next update.

 
Great (and respectful I might add) conversation on the upcoming environment from everyone. I really enjoyed reading that. This is an extreme modeled environment, as others have pointed out. If we even get 50-60% of that CAPE, that’s more than adequate. A lot of your events this far north can get by (and thrive even) with 1500 k/j. 4000 would be icing on the cake.

I’ll be interested to see if Trey has changed his thoughts on tomorrow’s set up. He was very bullish on the Oklahoma threat and thought the northern threat would be a giant QLCS because the crashing cold front. With some of the updated model trends, I’d like to hear his thoughts now.
 
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