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

[Luke Penney]

The upper Midwest looks to be getting yet another severe-weather event on Friday. (To add a joke to the discussion on whether Tornado Alley might or might not be moving, maybe this year indicates Tornado Alley is moving to the Midwest .) Severe potential also goes down to the south Plains, but I don't normally look closely there because it's so far from me.

At first glance, I wasn't expecting much from Friday in the Midwest since it's a cold front with high-level winds at a somewhat-similar orientation as the front: That's a recipe for linear storms undercut by cold air. However, GFS and NAM both forecast storms ahead of the front that are initially at-least-somewhat discrete and in a tornado-favorable environment. NAMST and RAP forecast the storms in a messier mode, but those models tend to do that in general, and they do forecast favorable conditions.

This time, the models are also looking quite similar to each other, two days out. If the outlook is still like this on Friday, I'd favor a target in or near southeast Iowa (at least, within the area that's not too far a drive from me), with an expectation that storms are to likely initiate in early afternoon.

 

[Dan Robinson]

A positively-tilted wave, cold front, boundary-parallel flow and the closest storms more than 4 hours away is usually a no-go call for me. That might be me having to work Friday night talking, but I think better things are coming to spend $4.50/gallon on.

 

[JamesCaruso]

Southern Plains target looks quite compelling - pretty classic triple point setup with a nice tight dryline. There are things to nitpick if you wanted to see a really high-end setup, like maybe surface winds more backed for better low-level hodographs, but really there is not much not to like about the thermodynamic and kinematic parameters. And there likely will be some localized better backing that is not currently resolved by the models. Only real downside as a chase day is the double-edged sword of a fairly obvious target, and NW OK is going to draw a swarm in that area on a Friday. To my eyes the NAM depicts more difluence aloft a little further south along the dryline, but either way it’s a relatively small area of interest with details to be resolved on the day-of.

 

[Luke Penney]

For the upper Midwest, recent model runs have shifted around the best locations a bit, and shown a significant risk of linear mode to the storms. However, they also show a large, very favorable area for tornadic supercells (and hail), so I’d expect any discrete storms to have a lot of potential.

 

[Patrick K]

A positively-tilted wave, cold front, boundary-parallel flow and the closest storms more than 4 hours away is usually a no-go call for me. That might be me having to work Friday night talking, but I think better things are coming to spend $4.50/gallon on.

I’d be out as well. The best parameter space is encroaching into the hilly forested areas of central Wisconsin, bleh. Even then it seems like sups will need significant time to organize such that they’ll likely be subject to interference owing to parallel flow, resulting storm motion, and possible undercutting by crashing cold front.

As of right now, my feeling is that, as is often the case, storm mode is paramount. Best chance for sustained supercell structures along the dry line in OK into southeast KS where storm motions will be more favorable. Sure, still some chance of ample window of discrete mode near the surface low in the upper midwest but I'm skeptical.

 

[Zack Ruddle]

For upper Midwest...

This one is a tough one for me to gauge. Model runs giving some hope of discrete cells, but conflicting on how quick the QLCS transition will be. Seems the best potential is right over the driftless, not a fun place to chase.

Looking like a similar but more volatile setup compared to Monday, but between geography and how linear things are modeling at the moment, this might be one where staying home is the better play for me. "Higher Ceiling; Lower Floor"

Best of luck to all who venture out.

 

[Luke Penney]

For the upper Midwest, today's HRRR and NAMST have not been showing much in the way of discrete supercells, but have had mesocyclones at the south end of lines of storms. I agree that one of the major things that will affect tornado potential tomorrow is storm mode.

To add another perspective, the Storm Prediction Center does think there are good odds of discrete supercells: "While an eventual squall line may take shape late in the day, scattered supercells appear likely after about 19Z ahead of the developing low and as dewpoints rise rapidly."

I don't know why this is - perhaps due to strong forcing ahead of the front?

The best parameter space is encroaching into the hilly forested areas of central Wisconsin, bleh.

Yeah, the Driftless Area is a much worse chase location than south of it.

possible undercutting by crashing cold front

I'll argue that I don't expect this to be much of a factor: Every model run I've seen has put at least the first round of storms well ahead of the cold front.

(For the overall evaluation, I will add that I'm deciding based on starting in south Wisconsin, not doing a road trip to get to a target area, and those have considerably different calculus.)

 

[Bobby Little]

Gave a thought to heading out for the Midwest chase till i added it all up.

Not liking : 6hrs to Davenport. 1 hour north to target area Lansing Iowa.
Chasing in the Wisc jungle. The Mississippi. Most models have weak DWPTs.

I do like: CAPE seems good. GFS DWPTs. Enough sheer. Early Chase time (maybe 18z) on those discrete cells ahead of the low out of Iowa.

If this chase stayed more to the south, i might venture. Besides i like that TP/Dryline setup in OK much better.

 

[Jesse Risley]

Some of the models are showing discrete sups invo the triple point from the Hwy 20 corridor into Grant County, WI or the driftless area. Others want to quickly congeal the convection into a linear mode. I don't doubt that there will be some potentially strong tornado reports, at least 1-2, somewhere ahead of the low in far E IA, NW IL and/or S WI. The most likely widespread threat in the upper Midwest is likely to be damaging winds but it's possible that the southern Plains target ends up being an unexpected tornado producer.

 

[Mike Smith]

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.

 

[Ben Holcomb]

00Z Raobs tonight (DDC, AMA, TOP, OUN) showing significant dry air aloft. I have some serious capping concerns for the southern mode outside of strong forcing right on the cold front.

 

[JamesCaruso]

Well my post yesterday morning didn’t age all that well. That’s what I get for posting after a couple of quick big picture looks without a full analysis as if I were actually able to chase the day. That said, I still think there’s a high ceiling along the OK dryline. I did see the stronger capping that Ben noted, but think it can be overcome. Any storms that form will be in a great environment characterized by high STP. The Norman AFD flags this, while also noting clouds could inhibit convection south of I-40.

 

[Dan Robinson]

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.

 

[Matthew Crowther]

In Blackwell, OK, the CAMs continue to show supercell development rear the triple point Like this area beginning further west a bit. Could d be a relatively early show, CI as early as 3-3PM? If there is a weak mesolow, east of that may be OK for a couple of hours, as the cold front would be surging farther west, at least that is the hope. If the latest HRRR is right the farther north play gets messed up by early convection, but other CAMs do not have that's cenario, In a couple of hours it will all be about monitoring the surface map and sat pics.

 

[Jesse Risley]

Definitely looks like a chance for an isolated supercell or two in northwest Oklahoma ahead of dryline/CF proximal to the triple point IF the CINH can be overcome. That's where I'd be lurking if I were playing the southern target. Across the northern target models continue to signal a wind shift associated with what may be a meso-low that develops over far E IA. There have been consistent signals for discrete supercell development across both E MO and NE IA before the main line roars through. The most substantial tornado potential still appears to be proximal to that US HWY 20 corridor or wherever those discrete storms materialize, if they do, ahead of the surface low. Parameter space would definitely support a strong tornado or two but things look to congeal rather quickly where the threat transitions to mesovortex and QLCS tornadoes and then a damaging wind threat where wind gusts over 80 mph are possible.