2026-03-10 EVENT: IL/IA/MO

[Luke Penney]

On Tuesday, we might have our first event within easy day-trip distance of me in Wisconsin, so I'm creating a thread for it.

(Looks like there's also a southern target; I think it makes the most sense for that to be a separate thread, but let me know if I should edit the title of this one to include it.)

Strong winds from the south will bring warm, moist air northward, with surface temperatures forecast in the 70s and dewpoints in the 60s. Moderate instability is forecast, with MUCAPE of 1500-2500 J/kg over much of the relevant area. Mid-level lapse rates are good, getting up to ~8°C/km. NAM and GFS disagree on whether there will be much in terms of low-level lapse rates (probably because NAM is forecasting clouds and GFS is forecasting clearer skies).

As is to be expected at this time of year, lower CAPE is made up for by stronger shear, with 500 mb winds getting to around 60 kts, depending on location. 0-3km SRH is concentrated along a temperature front, maybe getting up into the 400's or 500's m²/s² there.

The warm sector is initially bounded to the north by a warm front that switches to being a cold front (with models differing on exactly when that happens). That front also introduces extra vorticity.

(Image from College of DuPage)

The best hodographs are north of the front, but instability is only south. Right along the front might be an interesting location because of that and the vorticity, if the cold air doesn't undercut the storms too much.

(Image from Pivotal Weather)

There's a little bit of capping, and I'm seeing initially-discrete storms in the models.

The models I've checked (mainly NAM, GFS, ECMWF) all show a relatively similar set-up.

Big question marks to me are the degree of cloud cover earlier in the day (with NAM and GFS disagreeing on that) and when exactly the warm front will become a cold front.

I think a storm getting on the warm front and taking advantage of the favorable winds there would be promising; otherwise, I'd look for warm-sector supercells in general.

(This is the first time I've created a Target Area thread, so let me know if I've made mistakes or missed anything big.)

 

[Dan Robinson]

The medium-range 18z models are in good agreement on the surface and upper air charts looking a lot like yesterday's (Friday March 6). The surface charts are uncanniliy identical: dryline, cold front and warm front all in the exact same areas. The main difference is the jet streak is shown ejecting a little later, but there is decent flow pretty much everywhere. There is more of a signal for sustained convection in the open warm sector this go around.

 

[Jesse Risley]

This one is right in my backyard. It will definitely be interesting to watch the models and surface feature interactions. As of right now a pretty solid bit of CINH until around 00z. The shorter-range American suite is just coming into the picture with the 12z/08 runs showing convection INVO the warm front/triple point and points east between 0z/11 - 03z/11 and this is coterminous with the ECMWF's solution as well showing robust convection south of I-80 by 03z/11.

There are some hints at initiation convection near the low around 0z/11 along the US Hwy 2 corridor in SE IA on the 06z run of today's ECMWF. Definitely a lot of overlap of parameters with anomalous warmth for early March. These setups sometimes produce surprises along the warm front further east of the low, e.g., across N IL or possibly into S WI (if the front makes it that far north) too, if convection can fire, so keep an eye on that potential as well as the situation evolves.

 

[Luke Penney]

I'm seeing a lot of variation in the models I'm looking at for when storms initiate, going from from 18z (1 PM CT) to 0z (7 PM CT). The latter would be disappointing, because that's sunset.

(Widespread convection, especially along the front, happens after dark regardless, but that's a good thing for chasing.)

 

[Jesse Risley]

I'm seeing a lot of variation in the models I'm looking at for when storms initiate, going from from 18z (1 PM CT) to 0z (7 PM CT). The latter would be disappointing, because that's sunset.

(Widespread convection, especially along the front, happens after dark regardless, but that's a good thing for chasing.)

It looks like to most substantial upper-level forcing holds back until closer to 0z which may be why the models are initiating convection later given the robust CINH. I'd like to see a stronger low with better backed surface winds but perhaps the relatively more diffuse surface low will provide enough of a focal point for a discrete cell or two INVO the warm front as parameter space is otherwise favorable in that narrow region southeast of the main surface low. It appears to me that there is also a subtle prefrontal wind shift or pseudo-trough across the warm sector in W IL which may be the focal point for the more robust convection around 0z across C IL just west of the IL river.

 

[Andy Wehrle]

I think I'm going for an initial target of Galesburg, IL. Multiple models seem to be maximizing the parameters around there near 0Z Wednesday, and some initiate discrete convection. An area of better-backed surface winds just ahead of the triple point appears on some models near or just east of there, as well. In addition, just anecdotally there seems to be something about the west side of the Illinois River valley from Beardstown on up to Peoria; multiple notable tornado events have occurred there in recent years.

@Luke Penney I'll also be departing from Madison after getting off work at 1 PM.

 

[Andy Wehrle]

This is shaping up to be the classic battle of subtle forcing vs. capping that makes or breaks so many chase days. Do you get no storms (at least before dark and within the warm sector), a messy convective blow-up, or just the right balance leading to a discrete tornado machine within the last hour of sunset? There's enough evidence in favor of the latter, combined with the progged parameter space, to make it worth the trip in my opinion.

 

[Dan Robinson]

This looks like a case of do you go into northern Indiana and hope for the daytime lead cell, or hang back with everyone else? The lead storm shown now looks like it might be at risk of being elevated north of the front/lake breeze. You won't catch it if you're west of it, though, so there's really no way to hedge between both areas.

 

[Mike Smith]

I think SPC may have been premature taking the KC Metro out of the 5% hatched area in its 1730Z Day Two outlook.

The models this afternoon...

• Holding a bit of a low and triple point NW of KC.
• The 12Z ECMWF has KC right in the right rear quadrant of a 110 knot wind max at 250 mb at 7pm CDT Tuesday. That might be enough to break any cap. The max strengthens during the evening.
• Multiple CAMs have rotating thunderstorms going across the area.

While I think the better chance is SE of downtown KC, I think SPC had the right idea with its morning Day 2 (attached).

 

[Bobby Little]

Lots of differences in the models. RRFSA looks best for early storms. ill probably target mid afternoon in a triangle of LaSalle - Decatur - W of Peoria, looking for better dew pts and hope for discrete cells south of the warm front/boundary. Just hoping the boundry doesnt lift too far north so i can stay out of Chicagoland and not have to rely on cluster f%$k convection and large hail at dusk. Cape looks good. I can always travel east along the warm front into Indiana on the way home also.