09/13/08 FCST: IL/IN

[David Draun]

Looking at the KLOT forecast discussion this morning, I see they have highlighted a tornado threat in parts of the Chicago Metro and NW Indiana tomorrow afternoon. It appears shear and ground-dragging LCL heights with modest instability and very deep tropical moisture support a threat for low-topped supercells and an attendant threat for a few tornadoes. Low level shear will increase some as hurricane Ike moves northward into the MS valley.

The threat is all based on clearing and storm mode, but that jet streak over northern IL looks pretty impressive on the 36hr NAM time-frame. The same feature shows up on the GFS, but weaker and farther north. KLOT took the time to mention this, so I will be watching it as well.

 

[Jared Farrer]

It might be interesting. I personally I am not confident in it clearing out letting in insolation. If we can get pockets of better thermodynamics. With the boundry the way it is I think there is potential. I will be watching this closely too. We could get an isolated event here tomorrow. And I am curious the kinds of structure we can get out of this kind of setup.

-Jared

 

[Travis Carlson]

I’m also intrigued by tomorrow’s setup. Already tonight some low-top supercells formed near Kansas City. MO. That begs the question what about tomorrow? Well I think it indeed has some possibilities for sure. Weak to moderate instability with sufficient low-level shear peaks my interest. I’m thinking right now the I-55 corridor depending on where a differential heating boundary may set up. That’s a good area to chase as well with a good road network. Moisture definitely not a problem and they'll be lift...all you need is just a little bit of instability like we saw today in Eastern KS and Western MO. I’ll definitely be keeping my eye on this one with a short drive from DeKalb, IL if things look good tomorrow.

 

[Adam Lucio]

Certainly not a setup I will make a target zone. Im not too confident in the instability, CAPE values dont even look higher than 500.

Wind fields dont look to bad and it even looks like winds may back over the northern half of IL. Getting localized pockets of clearing will be the key obviously. I imagine things will be quite hazy with some ground hugging bases given the LCL levels. I will be watching for anything worthy of a last minute bolt out of the door thats for sure.

 

[Dan Rupnow]

Definately not the most ideal setup tomorrow. Convergence along the front, mostly unidirectional SW winds parallel to the boundary, and little CINH is gonna make it hard for anything to stay somewhat discrete. Looks like a straight line wind threat, but I wouldn't rule out an isolated tube, especially in N. IL or far S. WI in closer proximity to the surface low and the 250mb jet max. Copious moisture will yield rediculously low LCLs. 00Z NAM has CAPE values aoa 1000 j/kg for the 21Z timeframe for most of N. IL and S. WI but obviously that all depends on how much insolation we get.

Not expecting much tomorrow, but you never know.