6/27/08 FCST: IA/IL/MO/WI/MN/IN/MI/KS/NE/OK/TX/OH

[Brandon Sullivan]

Another day of significant severe weather appears probable on Friday Across the Central US..

A rather widespread Wind/Hail event appears probable. With a tornado threat highest in the Upper MS Valley across Eastern IA and Northern IL.

Good low level kinematic support will be in place, along with forecast CAPE Values of 3500+.. Assuming morning convection clears out, the atmosphere should rapidly destabilize by mid afternoon. Severe storms should develop in the afternoon. The best shear and helicity values and associated tornado potential lie across northern IL and eastern IA, where surface winds are forecast to back to the SE. It looks like a cap might stay in place long enough to hold stuff until the afternoon.

 

[Andrew Stoller]

Has the makings for a bigtime wind/hail event if you ask me with little to no tornado potential - upper flow is more northwesterly and surface winds are majorly veered. The surface low is northwest of Lake Superior by 00z and that's where any backing takes place - across southern Canada and extreme northern WI. Looks like the cold front will also sweep through in a big way by 00z

 

[Colin Davis]

http://www.rap.ucar.edu/weather/model/displayMod.php?var=eta_sfc_mslp&hours=hr36hr30

Veered surface winds all the way into Wisconsin. Enough said.

Oh, but wait...not enough said. We're veered at 850 too!
http://www.rap.ucar.edu/weather/model/displayMod.php?var=eta_850_wnd&hours=hr36hr30


Hooray for unidirectional flow! Tomorrow, there will be two tornadoes. Both short lived and part of a linear complex.

And I won't be searching for them, lol.

 

[Scott Weberpal]

I won't throw tomorrow out the window quite yet, there is still a decent chance of tornadoes along any active boundaries in the upper midwest. Much of todays activity in Nebraska and Iowa will continue through Wisconsin and Northern Illinois tonight and should leave numerous boundaries in it's wake. It won't take S or SE sfc flow to get good directional shear when H5 flow is westerly.

Mesoscale accidents are what make chasing great.

 

[Brandon Sullivan]

You said it Scott.. And that is one thing that will highly influence my target tommorow..

It wont be a wedge fest, but my eyes would be on N. IL as a tornado spot.. If thats where the "two" occur, thats where I will be..

But look at this.. Intriguing.. Maybe I should stay here... lol

http://www.rap.ucar.edu/weather/model/eta30hr_sfc_sreh.gif

 

[Andrew Pritchard]

Even with as bad as the low levels are I don't think that's the biggest problem.

500 mb winds are variable at about 15-20 knots across northern Illinois where most boundaries and the slightly better LLJ support will lie. Boundaries don't require a lot of shear, but you generally want some shear.

I'm not chasing so I may be slightly biased, but I'm not sure why the SPC kept a 30% hatched in there and can help but wonder if that's maybe why some posts in this thread are so strongly worded.

Taking a look at the models it's a very conditional day depending on how things play out tonight. It will almost certainly require some sort of boundary, and even so things could be HP or multicell with such terrible flow aloft.

Worth watching if you have time to play the boundaries, but a significant event? That's going to require some big changes in the next 24 hours.

Southern Wisconsin is probably going to be the best bet. If I weren't busy I might have gone up and started my 4th of July vacation up there a bit early. There you'll get a bit better upper level support so things might have a better chance of going supercellular.

Brandon - You could stay there with that helicity map that you posted... but you want to overlay that with this instability?

http://weather.cod.edu/forecast/ETA/GL/etaGL_0_cape_30.gif

It improves by evening, but then the shear is more "whack".

 

[Colin Davis]

Unless the storm is within a 10 mile radius of my house, I will not chase a setup with veered winds at the surface. I have NEVER seen anything worth chasing with surface winds at the southwest. Boundaries help, but with 20kt at H5, just about everything would be poorly organized at best.

This just isn't the kind of day I'd drive even 50 miles for.

 

[Andrew Pritchard]

Pretty obvious MCV coming out of southern Iowa right now pushing into western Illinois. That's going to be as good a focus for thunderstorm development as any today I think. Still not amazing shear profiles, but forecasts are at least showing more southerly flow at the surface, and that mcv may do a little helping. Most problematic area is still the flow at the mid levels. If we can get 35 knots, we -could- be okay.

I'd still bet on multicells being the main threat.

Just have to watch that thing as it pushes east.

 

[Jim Zandonai]

Current situation of the area here in N.IL doesn't look too good..besides the storms in S.IL and the cluster north of Madison WI..there isnt really anything to set off rapid storm development. Plus this cloud cover is holding temps down. Cape good and dewpoints around 70 but wind fields are poor..There is clearing in Iowa ahead of an advancing frontal boundary though and I think something will develop there yet but as sunset approaches will probably die out crossing the MS river. Disappointing so far because some parameters are very good but just no real spark here ..yet. Well at least it looks like I will save money by not having to buy gas today..!