7/3/07 FCST: MN / IA / IL / WI

[Brandon Sullivan]

A Shortwave will top the ridge early in the period. Convection may fire along the boundary on monday. The main show will be on Tuesday, as the boundary and associated cold front continue southward. Convection will fire during the afternoon. Storm motion will be to the southeast. High CAPE and high shear values will allow for supercells, rotating structures. The fast movement of the front should keep the heavy rain threat down somewhat, but with storm motions paralell to the front, always have to keep the threat in mind. Models still somewhat varied in timing, but have been continuous with the extent of the threat.

Small Quote From DMX for topic support

IF THIS EVENT WOULD UNFOLD...COULD BECOME A FAIRLY
EXPLOSIVE...HIGH SHEAR ENVIRONMENT WITH THE POTENTIAL FOR ROTATING
STORMS WITH A MODERATE SEVERE WX THREAT.

 

[Brian Stertz]

May want to add sections of NW Kansas and SW Nebraska to this forecast thread. It looks like the ETA was catching on to a pretty nice 500mb wave moving through with 35-40kts. Not a huge tornado threat but one worth mentioning as a possibility on the boundary near the NE/KS stateline. May be an interesting setup if the lower level winds are a bit stronger and 700mb a bit cooler. Directional shear appears to be pretty darn good and ML CAPEs forecasted for Tue. evening by ETA are around 3500 j/kg. Is worth the gamble???

 

[Dustin Wilcox]

Also have been monitoring the potential for the NE area, the ETA has been consistent with this wave since at least yesterday 18Z (when I first started watching), per this afternoons 18Z its just a little farther E with the wave then previous runs with 40-50kts at 500mb in the C NE area, it has also been trending towards cooler midlevels bouncing around between 11-12C at 700mb, its been showing decent LL backing in a localized area with 20-25kts at 850. If the setup continues to show some promise my chips will certinly be in the pot as I wouldn't want to miss a July supercell in C NE.

 

[Brandon Sullivan]

I agree that those areas should be added. I will probably play local though. Some of the local offices want to make the main day of concern the 4th now. So now Im thrown for a loop.

Dustin- I really like the avatar.

 

[Derek Weston]

Big fat differences between ETA and GFS. Central Neb/SD or central Iowa? I'll learn more tomorrow I guess.

I'll go for it if it's decent enough within 2-3 hours or so from Cedar Rapids. (unless it turns into a really impressive setup, then I'd drive a little longer)

 

[Dustin Wilcox]

Big fat differences between ETA and GFS. Central Neb/SD or central Iowa? I'll learn more tomorrow I guess.

Not only between the GFS and the ETA but also huge differences in the ETA run to run, the 0Z is not nearly as impressive as the 18Z or the previous 3 runs for that matter (slightly warmer midlevels and much more veered Low Levels), Still many runs out and expect we will see the solution change with each run just hope its eventually for the better.

 

[Brian Stertz]

Kind of looks like a potential boundary landspout/weak tornado type of setup tomorrow. Decent directional shear along/north of the boundary. Moist unstable air on both sides of the boundary from C/SW Nebraska into extreme NW Kansas with ML CAPEs of 2500-3500 j/kg. Will have to watch this to see on the models where the boundary decides to hang up or slowly drift southward tomorrow afternoon.

 

[Jim Zandonai]

As far as north IL. goes looks like a night event. Spc has us on the very south end of day 2 and north end of day 3. Typically this means we either get a night event if anything and the next day action is south and east. So not too excited at this time here at home unless the night event carries into the day 2 as a line moves through. Anyone see any derecho possibilties anywhere ? Ironically we got hit with one on July 5th A.M 2003..course the set up was alot different.

 

[Michael O'Keeffe]

I really want to chase tomorrow, but it may be to much of a gamble. I am liking the severe parameters right now though in the SW NE area. Sig Tor is close to 5, Sup parameter is around 40-50. There are more south/se winds in SW NE/ex NW KS. All the parameters are bullseyed very near McCook, NE. I hope the models can improve a bit, but I may give it shot tomorrow and get at least some nice landspouts/weak tornado. I'm desperate right now with sever SDS. The SPC also extended the 30% too.

 

[Derek Weston]

Latest NAM making NE to N Central Iowa interesting... winds best up near along the Minn/Iowa border, with impressive CAPE in the noted region. Largely uncapped. Shear looks to be the tricky part... WSW 850 with NW at mid and lower levels. Don't know if that'll get it done or not.

Latest GFS seems to have the threat more N central Iowa/ S. Minnesota. (winds being a little more towards unidirectional)

It'll be interesting to see where the SPC goes with this.

Last edit: SPC basically verifies what the models were hinting at. Keep an eye on the surface low as it heads SE through Minn into Iowa.

 

[Kory Hartman]

I think we can safely add SD and NE to the thread... latest SPC hail and tor outlook puts a bullseye on Sioux Falls and points east.

 

[Brian Stertz]

LCL's according to the latest RUC show that mainly high based severe hailers are possible across C/SW Nebraska into NW Kansas and NE Colorado. Today's tornado threat looks like it will focus on SC/SE Minnesota into extreme NC/NE Iowa and SW Wisconsin where more the best EHI and more favorable LCL's are forecasted by afternoon.

 

[Derek Weston]

Yes, liking SE quadrant Minnesota the best right now. Best 0-1km SRH and LCLs.. Helicity isn't outstanding, though... (less so than the other parameters mentioned) Wouldn't be surprised to see the SPC move the greatest tornado threat to S Central, SE Minn southeastward towards NE IA and SW Wisconsin. I'm hoping things develop a bit west of the Mississippi river (for obvious reasons) however.

 

[Bob Hartig]

Haven't looked at models today, but last night's NAM spotlighted eastern Iowa for me. It's now old data, admittedly, but at the time I was thinking that the area around Washington, Iowa, north to around Iowa City, looked pretty good: on the edge of 3,500 SBCAPE and a bullseye of MLCAPE, good EHI and 3kVGP, with a 3 sigtor lurking in the neighborhood. Makes no practical difference as far as I'm concerned since I won't be chasing, but I will be armchairing it with my laptop.

 

[Craig Maire II]

I am just taking off from Waterloo Iowa and will be heading to Albert Lea MN. An outflow boundary/MCV along with ML Capes aoa 2500jkg and effective shear of 35 to 45 knots should lead to scattered severe thunderstorm/supercell development by early this afternoon with the possibility of some very large hail and a few tornados esp. in far northern Iowa and south central MN.