2026-04-17 EVENT: IA/IL/WI/MO/KS/OK

[Patrick K]

The cold front is poised to blast through everything that forms along it. It's already hauling through Kansas with winds behind it pushing twice as strong as the southerlies ahead of it. There have been enough model signals for open warm sector storms in SE KS/SW MO/NE OK that I think that would be my play, though the lack of any distinct boundaries are making it a toss-up on specific areas. I'd probably head to Fort Scott and move to wherever the Cu fields are pointing.

The warm sector storms are the obvious play for northern target. Storms along the front may tend to be undercut by the cold front, otherwise I think this could be a higher end setup. Someone above apparently thought I had previously meant that the WS storms would be undercut? lol...

I also still agree with others that near the dryline in OK, and also into SE KS, and possibly into MO as well has the greatest probability of sustained supercell structures. Models, especially the HRRR, have been a bit more bullish with time in terms of storm motion (right movers), orientation w.r.t. the forcing gradient, and a bit more low-level backing of winds compared to earlier runs. I'm expecting to see a few supercells pop off the dryline and maintain discrete mode long enough. Additionally, may see a TEC into KS and/or an open sector storm there ahead of the front.

 

[Brian R.]

I'm thinking that most of northern Illinois and southern Wisconsin the main threats will be damaging winds and flooding. far southwest Wisconsin and far northwest Illinois may get into some supercell action, but even there the main threats look to be mostly damaging winds and a high flooding risk.

 

[John Farley]

Not chasing today, but have been watching online. I would say that the storms along the cold front have thus far remained somewhat more discrete than I thought they would.

 

[Patrick K]

Not chasing today, but have been watching online. I would say that the storms along the cold front have thus far remained somewhat more discrete than I thought they would.

Agreed. On mosaic radar it looks like initial line was undercut quickly, which then generated new initiation downstream. Instead of discrete initiation -> quick linear mode, we got discrete initiation -> undercutting -> new discrete initiation downstream.

 

[Brian R.]

I will be going out here in northern Illinois around Rockford here in a little bit, mainly because it's a "backyard" chase.... but really think by the time they arrive between 7-10 they will be already weakening substantially.

 

[John Farley]

I will be going out here in northern Illinois around Rockford here in a little bit, mainly because it's a "backyard" chase.... but really think by the time they arrive between 7-10 they will be already weakening substantially.

7-10? You have a confirmed tornado just north of Rockford now.

 

[Brian R.]

7-10? You have a confirmed tornado just northeast of Rockford now.

meaning for the Chicago metro area. I heard about that tornado. From scanner live feeds sounds like a strong one too.

 

[Jamie H]

Agree with SPC with regard to the Upper Midwest threat, so I won't say anything about that.

I think there will be a second area of elevated threat from west central Missouri and east central Kansas into the Wichita-south central Kansas area and into north central Oklahoma. If supercells go up in east central Kansas, giant hail > 3" and strong and maybe violent tornadoes are possible. Here's why:

• CAPE forecast (HRRR) to be 4000+j in this area.
• Fast-moving short wave.
• 200 and 300 mb winds in excess of 100 knots. The 18Z RRFS had a small area of winds of 130+knots!
• Difluence over the threat area.
• I suspect a mesolow will form in the EMP-ICT area with a dry line to the south. Earlier HRRR runs have temperatures in the low 90's behind the dry line in southern Kansas. Strong temperature contrast.
• Finally, the forecast soundings with the new 00Z HRRR have a significant temperature inversion that still exists at 19Z. This would tend to keep the "messy" precipitation at a minimum. If there are two lines, generally the lead line will have the supercells and a second line (if broken) will produce damaging winds and a few tornadoes. If a solid line, QLCS tornadoes (maybe) and damaging winds. With 4000 j of CAPE, there will be plenty of energy for two severe lines.

Good luck and be safe tomorrow. It could be a dangerous day! Rain-wrapped tornadoes possible.

Addition at 11:50pm. The HREF calibrated 24-hr tornado probabilities are attached. I've found this to be pretty good guidance over the years.

Just wanted to note this was good insight and covered the 'secondary' area very well!

 

[Randy Zipser]

This post actually encompasses the entire week ending in 2026-04-17, however I'm putting it here since Friday was the most dynamic day of that outbreak. The link below is a FoxWeather story (posted on MSN) recounting a day-by-day look back at that outbreak event:

April tornado outbreak causes devastating damage in multiple states | Watch

 

[John Farley]

As of a couple hours ago, 59 tornadoes have been confirmed by NWS damage surveys on April 17. Below is a list of the CWAs I have seen damage surveys from, and the number of tornadoes in each:

ILX-19
DVN-7
LOT-7
MKX-8
GRB-2
ARX-10
LSX-2
SGF-2
OUN-2

Most of the tornades, as is typically the case, were EF-0 or EF-1, but there were two EF-3s and also several EF-2s. Note that the vast majority of these tornadoes were in central Illinois or farther north. I believe only 6 anywhere farther south than I-72 out of the 59.