06/29/2005 TALK: MIDWEST

[Craig Maire II]

Wow

I am anticipating an HIGH risk will be issued tomorrow for portions of MN, IA, WI, etc. I will be chasing in Iowa (where I live ) and am targeting the I-35 area for supercells with very large hail and a few tornados tomorrow, mainly after 4 pm.

 

[Alex Lamers]

Nobody is concerned about capping? The GFS fails to generate much QPF over the currently hyped areas. Hopefully this gets resolved shortly.

...Alex Lamers...

 

[Tim Gonyo]

Originally posted by Alex Lamers
Nobody is concerned about capping? The GFS fails to generate much QPF over the currently hyped areas. Hopefully this gets resolved shortly.

I believe....the cap will break at about 4-5 pm over S WI, and supercells will rapidily develop after that and I agree the best tornado potential will be just west of Madison up towards Fond du Lac in that valley. They always seem to form there. We don't want a weak looking cap, otherwise the thing will be linear by 5 pm and it will be over with a marginal hail/wind threat.

Lets be optimistic, especially since its a backyard chase for a lot of us!!

-Tim

 

[Alex Lamers]

Well i think the main show would be with a squall line overnight. Based on GFS/NAM leading edges of QPF in 6-hourly intervals I have the following timeline.

00Z - approximately along a line from superior to red wing to mason city into SC IA.

06 Z - approximately from calumet mi to clintonville wi to madison wi to near davenport ia

12 Z - into western lower michigan...extreme east illinois and northern indiana.

This looks like a 01-07Z event for S WI beginning around La Crosse and ending around Kenosha. It looks likke more of a 4Z-10Z event across far E IA and into N IL.

Edit although the NGM from tonight pivots a rather extensive squall northeast around the low. Kinda screws N IL but Wisconsin would get absolutely raked with winds.

...Alex Lamers...

 

[Anthony Silver]

:shock: After being away for a while, this evening was the first chance I've had in a few days to look over the models...appears like a very nice setup will come together tomorrow evening over WI and IA. Looks like an excellent tornado/wind damage potential to me. CAPE and windshear values look excellent over that region, so long track supercells look like a strong possibility in my opinion. It wouldnt surprise me if the SPC places that area under a high risk in later outlooks considering all of the factors that are expected to be in place. If I can get the day off tomorrow, I'll probably be headed up to northeastern Iowa.

 

[rdale]

Keep a CLOSE eye on TAMDAR data http://www.crh.noaa.gov/tamdar

It was critical to several busts so far this year, and there are a few powerpoints showing how it helped some forecasters keep the dry forecast in place when many others were going gangbusters.

 

[Jayson Prentice]

Re: Wow

Originally posted by Craig Maire II
I am anticipating an HIGH risk will be issued tomorrow for portions of MN, IA, WI, etc. I will be chasing in Iowa (where I live ) and am targeting the I-35 area for supercells with very large hail and a few tornados tomorrow, mainly after 4 pm.

This is where I will likely be as well... Targeting the Mason City area for now. But, that can always change of course.

I'm going to play that cold front and hopefully get an outflow boundary out there (hopefully from the northern MCS that is forecasted) moving south. That would enhance shear considerably in my opinion. Or dependent on the warm front location I may hop on that. Mornings observations are going to be big in my decision process. But, either way I wouldn't mind meeting up with some other chasers if you are in the Mason City area. Pueter jeep grand cherokee...

EDIT - Anybody know of a good wifi spot in Mason City??

 

[Robert Dewey]

I'm wondering just how far east things will make it before dying out. Since derecho's generally move alot faster than the parent cyclone, are they still able to sustain themselves once they move away from the stronger shear (provided the atmosphere is sufficiently unstable)? The NAM has things blasting into western lower MI at 12Z (as Alex said), but then it quickly weakens things...

 

[Tim Gonyo]

I'm still maintaining my tornado forecast for SW/SC WI on WED evening.... MKE area forecast discussion does a nice job summing it up:

ANY STORMS DEVELOPING OVER THE WRN CWA DURING LATE AFTERNOON AND OVER THE ENTIRE AREA FROM EARLY TO MID EVENING WOULD MOST LIKELY BECOME SUPERCELLULAR GIVEN STRONG CLOCKWISE CURVATURE TO HODOGRAPHS IN LOWEST 3 KM AND ASSOCIATED HELICITY VALUES OF 300-500 M2/S2. BRN SHEAR...VGP... EHI AND BRN ALL HAVE VALUES INDICATING SUPERCELLS AND TORNADOES AS WELL.

Another snip from the HWO:

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTHEAST MINNESOTA...NORTHEAST IOWA...AND SOUTHWEST INTO CENTRAL WISCONSIN...

...IF ENOUGH INSTABILITY CAN BUILD DURING THE DAY...SOME OF THE THUNDERSTORMS COULD BECOME SEVERE. THE MAIN SEVERE WEATHER THREATS SOUTH OF THE WARM FRONT WILL BE LARGE HAIL AND DAMAGING WINDS. MEANWHILE ALONG THE WARM FRONT...THERE WILL ALSO BE THE POSSIBILITY OF A FEW TORNADOES. EVENTUALLY THE THUNDERSTORMS WILL EVOLVE INTO A SQUALL LINE WITH THE MAIN THREAT BEING DAMAGING WINDS. AT THIS TIME...THE BEST CHANCE OF SEVERE WEATHER WILL LIKELY OCCUR BETWEEN 3 PM AND 11 PM.

The Green Bay HWO indicates an outbreak:

THE STORM WILL PROVIDE THE LARGE SCALE INGREDIENTS NECESSARY FOR A SIGNIFICANT SEVERE WEATHER OUTBREAK ACROSS THE UPPER MIDWEST AND WESTERN GREAT LAKES REGION. EARLY ESTIMATES ARE THAT THE OUTBREAK WILL BE CENTERED ACROSS MINNESOTA...NORTHERN IOWA...AND WESTERN WISCONSIN.

Lets hope I'm right.

-Tim

 

[Ben Leitschuh]

Attm. I am targeting Lacrosse, WI perhaps farther north. I would like to be on that warm front, given its not too far north. Anyone who wants company give me a PM.

 

[Alex Lamers]

Well I upped my tornado probabilities in my outlook but im still favoring wind event. With the bulk of the shear in the 0-3 km layer...typically favorable of damaging wind events...have trended this way. I agree tornadoes are possible but after dark it would be unchasable anyways and probably really isolated. Warm front would be active in the afternoon PERHAPS if enough lift can get going from SE MN back into S WI. However, the upper level support does not arrive until later. If you want tornadoes you may want to be along the warm front or attack somewhere near the "triple point" along the MN/IA border area and attack the sups along the cf.

...Alex Lamers...

 

[Mike Johnston]

Surface moisture convergence a little more diffuse on the latest NAM run, than the prior run, but a couple of secondary areas of convergence drape down through IA. All factors together, I currently favor N Central IA. Could make a good case for a number of areas, but I like the way the dry SW flow at 700mb noses in there, and like to stay SE of the upper vorticity.

Something to be aware of: if chase takes you into Wisconsin, looks like storm motion vector will quickly shift from NE to SSE in central WI.

 

[Skip Talbot]

For now I'm targeting the Albert Lea, MN area. Here are a few numbers I pulled off a 0z forecast sounding that are of interest:

6km Shear: 57 knots
3km SRH: 515
1km SRH: 248
Craven Sig Svr: 93
EHI: 10.2
Sig Tor: 7

:shock:

 

[Mike Peregrine]

It will be interesting to see what happens with this convection that seems to be initiating over Kansas right now, with clutter moving toward Iowa overnight. There is a gap between the areas of convection that may allow for clearing tomorrow, but clutter is still a possibility that we may have to contend with. SPC currently seems to believe that initiation over SE South Dakota/SW Minnesota will occur during "early afternoon," leading a person to believe that the cap will not be a major factor. In the morning I'll be looking to see what ends up happening during the overnight hours. I also do not think that Iowa should be discounted, even though the sig tor index certainly seems to be absolutely in love with Minnesota right now. Looks to be ample SRH across the boundary in Iowa tomorrow, and I believe a few storms will likely fire down there. The question is whether they will be discreet, and whether they will be inclined to produce tornadoes in what looks to be a relatively high (but still do-able) LCL situation (hey, maybe local storm enivoronment will help out and lower the LCLs for us, per our recent thread in Weather & Chasing). Hopefully someone will find something interesting, though - all the best to those going out.

 

[charlie roswell]

More Wisconsin lurkers/newbies emerge...

River Crossings MN/WI

Hwy 63 Red Wing, MN

Hwy 25 Wabasha, MN

Hwy 54 Winona, MN

I-90, Hwy 63/14/16 La Crosse, WI

IA/WI

Hwy 82 Lansing, IA

Hwy 18 Prairie du Chien, WI

Hwy 61/151 Dubuque, IA

Be careful, most of the terrain around the Mississippi River sucks for chasing.