8/3/2004 FCST: MIDWEST

Feb 29, 2004
Rochester Hills, Michigan, United States of Americ
Started by requst...

Looks like there could be some action across a large area of the midwest Tue. Very high instability combined with good SRH (>300m2/s2) over portions of the midwest may allow for some good storms and possibly tornadoes. The best threat based on the 12Z ETA looks like it would be over southern IA...
Tuesday could be a very rough day for the corn belt if the ETA has any clue. I am looking at the warm front from NE Nebraska through NW Iowa and into central Iowa. Already have the day off and getting the car back ready for the road. Drooling at the 50+ bulk shear forecast near the Sioux City area. I like northwestern Iowa better than central and southern Iowa because of concerns about the cap. North of the low should have the best low level easterly winds as well. Warm fronts have been good this year, so why not try the luck one more time? The issues to me are what mesoscale events occur beforehand, where the warm front sets up, and the exact timing/location of the shortwave. Resideue cloud cover to be resolved that morning. But I love the idea of starting near Wayne, NE, in the mid afternoon and seeing the day explode.

Right now I plan on staying in Lincoln in the morning watching data and moving N or NE as the day develops.
Current 18z Tuesdsy- ETA showing high CAPE,SRH. LI for eastern Iowa to western Illinois with 70+ dew pt., 50kt+ winds @ 500, 30-40 kts @700, 20-30 @ 850. WxCaster shows Sig.Tor.,CSS, & SCP good for same area. Bl-6 wind shear is 50-60+kts east of quad cities, SFC-3 wind shear @ 30 kts. SPC is only mentioning MCS/bow echoes generally and Davenport HWO only predicting ,heavy rain, hail, wind for Tuesday.

What's everybody else's thought's for Tuesday ?

Jon Miller
I am in Ohio and pondering a trip out ti IN, IL or IOWA on Tuesday.

I am unable to get a very sharp focus on a target though. SPC has the broad area of 25% from Ohio to Nebraska and there text discussion is not very helpful in terms of choosing a specific target.

I guess I am saying that I do not have much insight into were to go. It does look like it will be worth going SOMEWHERE though.

My thoughts are to go as far W as is reasonable to prevent having to backtrack east, probably Danville IL. Get some data at around 8Z tuesday and see how the morning looks in terms of cloud cover. Then perhaps head as far W as central Iowa if needed. See what develops.

HWO's and AFD's for Indiana, Illinois and Iowa offer little in the way of additional insight. Hoping that by the morning things will become a little clearer.
I'd not recommend plans to chase in IL, and probably even IA tomorrow. If you can't be in s NE, I'd suggest staying home. Even if you can be in s. NE, if you don't already live near there, things look too conditional to justify a long drive IMO as at present the adequate deep layer shear is too far offset from the instability axis. Surface winds tomorrow are a mess in the Miss. R. valley - highly dependent on convective evolution which is anything but obvious, but forecast deep layer shear of 20 knots won't get it done in w. IL. If the frontal boundary across NE sets up a bit further north than the current ETA forecast - that could open a window of opportunity there for a good event. Otherwise, looks like a good day to be a lawn in parts of the Midwest as an MCS or two should be scurrying about.

I think Northern Illinois looks chasable tomorrow, perhaps from about Rock Falls to Peoria, depending on the warm front. I don't take ETA's diffuse surface features at face value because I think that if the shortwave verifies at ETA's projected intensity, surface features will react more favorably than shown.

This is an amateur observation, but it seems to me that with these late or early season events, ETA parses the mandatory heights a little too much. What I mean is that with a June-style s/w aloft, it still wants the surface to look docile as August. Still it's true that Big Mama Climo likes to stomp into these events and shove the calendar down our throats, so, after a 1500 mile bust we say: "Damn it, I'll never chase in [February, March, July, August, etc] again!" So maybe ETA is right to keep an eye on the season and resist anomolous patterns, which this summer has certainly been so far. The whole year, for that matter.

Still, with helicties around 300 m2/s along the stationary front, 3000 or more j/k CAPE is sufficient to spin an updraft or two and worth a 5% tornado probability.

ETA shows a lot of precip early and flow aloft suggest MCS evolution eventually, no question, but I think a small window of isolated storms could open particularly along the front between 19 and 21Z, if the ETA verifies with s/w passage.

My Illinois curse is approaching Naftel-ian proportions and so I'll stay home and watch the action on the internet. Good luck to all who go!
My group is heading to central and then western Nebraska.

As the model portrayal of the event continues to unfold, I think that my group is going to play north of the surface low as the ETA continues to indicate this is going to be a western event. Early guess is that we will head out to Kearney sometime in the mid AMs and stay at the UNK library until the early afternoon hours, and let the event shape up from there. 12 Z ETA noted bulk shear most adequate north of the interstate so we'll see how far north the warm front sets up. I just can't say no to easterly winds with 60+ dew points near Highway 83, though.

Of course, we'll see where the sunshine is on the boundary tomorrow.
Amos could be right - but I have very low confidence in this evolution. There is a signal in the ETA model that a small favorable low-level shear region develops leading the shortwave - but during this same period the cap appears to still be rather strong - so convection should be limited to the outflow boundary - which other than a possible line vortice along the bow, should limt the tornado threat IMO. So, I see a strong bow echo heading towards Chicago if the ETA verifies - definitely some potential for damaging winds with 35 knot 700 mb winds.

As for the seasonal disfunction of the ETA - I'll look around and see if I can find anything.

Originally posted by Glen Romine
If the frontal boundary across NE sets up a bit further north than the current ETA forecast - that could open a window of opportunity there for a good event.

A quick look at the latest ETA suggests this may be coming to fruition - rather nice setup coming together for parts of NE - definitely something to watch for if you live in that part of the country.

Well, on the 0Z the Illinois shortwave is gone. So I'd say Illinois is out of contention for supercells tomorrow. I haven't looked at NE or other areas at all, but it sounds like their situation is improving.
Things looks so-so for the IL/IN area tomorrow... Don't think I'm gonna head out. NE is looking good, particularly eastern NE and extreme western IA (moreso on the north side of the states given CAP to the south)... Relatively high CAPE with good helicities (ESE SFC winds) as well as some good energy sliding in at 500mb between 21Z-00Z... I personally think the risk is pretty good for supercells. Mid level flow is lacking, but the good 0-3km shear combined with non-linear convergence should provide for a few cells... ETA convective scheme also puts out some QPF in this region - So if the ETA were to nail it dead on, there will be something around precip-wise...

Also, a bit off topic... Check out the 00Z 48HR ETA over northern IN/OH - Very intense baroclinic zone for August (temps near DTX are around 60-65F, inceasing to 85F just a ways south)! Looks very much like convective feedback to me (given various factors, including the fact that this is the only run to show a wave this strong and the abnormally high QPF for that region/time of year). Anyway, still interesting...


Interesting for western IA. I am hoping something goes along the wf because I've had it with driving way west. Time for the data at home chase of the year. See storm from home and drive the short distance to it. No more of this, oh lets go to Ainsworth in August crap. Nice to see a decent low level jet. Forecasted LCLs along that front are sweet. We'll see. Hopes have been put on the back burner for a while now.
Per the SPC 0600 day 1 , the midwest scenerio has pretty well vanished
except for western Iowa - Wed 8/4 looks real interesting for IN/OH/MI area if ETA/GFS hold true - looks more like a spring setup but I'm a little bit suspicious right now.