7/27/07 FCST: IL/IN

[John Farley]

If this morning's NAM run verifies, it looks like there could be a small area of strong instability coincident with good directional shear from around Champaign-Urbana, IL southeast through around Terre Haute, IN. Like today, it will probably be an early show, with the best supercell potential shortly after initiation. It also looks like by evening, the best instability and shear are less in sync than earlier. I think this is at least a setup that bears watching for Illinois and Indiana chasers.

 

[Andrew Pritchard]

Certainly a day worth watching over eastern Illinois into western Indiana. Doesn't look like a huge day by any means, but it's certainly a respectable July setup which may produce a few tornadoes. Since the best area tomorrow afternoon looks bullseyed over me here in Champaign I might casually look into getting the day off.

My biggest concern will be the early convection. Whether there be precip or not, there's a good shot at decent cloud cover ahead of the system as it works its way southeastward. However, at this time the models are breaking things up by early afternoon allowing for strong destabalization over the eastern part of Illinois on the southern flank of the convection just SE of the surface low. In this area strong directional shear will be present with 45-55 knots of effective shear, and 0-1 km srh of 100-200 m2/s2. If we recieve the forecasted surface heating and are able to reach the forecast 2500-3000 j/kg sbcape values we could see a supercell or two develop in eastern Illinois and track ahead of the surface low into western Indiana.

John has the target area down pretty good in his post, so should I decide to look into taking work off I'll probably hang here at home for a while to let things unfold. That all is of course, should the models look remotely the same this evening.

 

[Andrew Pritchard]

Bleh. Such is life... I get out of work and everything looks crappier. Still looks like a marginal shot at some severe weather tomorrow, but likely further south than it looked earlier, and probably far enough south that my broke self won't bother venturing out. I'll keep an eye on it since initiation will likely still occur somewhat nearby, probably between I-72 and I-70 between Champaign and Effingham.

There's enough helicity early in the day near the surface low that I still think a spin up tornado or two isn't out of the question, but unless tonite' run is wrong I don't think we are looking at the supercell threat we were seeing on the morning run. By 0Z the surface low is a disorganized mess, and the surface wind fields become total garbage so by evening I think any storms will be multicell line segments, at best.

Here's to hoping for a change I suppose...

 

[John Farley]

Well, it certainly doesn't look any better this morning, and widespread cloud cover to boot. It looks like whatever marginal chance there is will be farther southwest, near my area, as both the RUC and NAM now show the best combination of instability and shear over eastern MO and southern IL. Perhaps some outflow boundaries in this area from the overnight convection to the north and northeast will become the focus for storms this afternoon. So, I will just hang around home, watch radar, and head out if something decent looking pops. But I am not holding out much hope for today.