10/3/06 FCST: MN / IA / WI / IL / MI

[Jesse Risley]

Agree with the Northern track forecasts...I would think the triple point area (IL/IA/WI confluence) would be a good target. I think the instability will be long gone before everything reaches us here in Western Illinois.

 

[Scott Lincoln]

Unfortunately, it looks to me like the cap is going to be a big player today. The 700mb temps around 7.5C-9C dont seem so bad at first, but go down to 850mb and you have 15C-17.5C, which is roughly 85-90F when cooled adiabatically down to the surface. It also does not appear that the mid to upper level lapse rates are as good as they could be. A ETA Bufkit sounding from Rochester shows that even if a parcel can break the cap at its weakest point around 5pm, the environment above that will not be all that favorable for quickly accelerating the parcel. Seems to me like the only hope would be for higher dewpoints than predicted, so that lifted parcels can reach the LCL soon and the cap will become quickly lesser of an issue.

The WRF 4.5 km also seems to reflect this, not forming any convection until after dark along the warm front, and not until midnight along the cold front/dry line area.

 

[Skip Talbot]

I was a little surprised to see the upgrade to moderate. The 0z ruc forecast hour is still showing only 20 knots of 6km shear through most of the risk. I've generally heard of and used 30 knots as a threshold for sustained supercells, let alone "intense supercells" as per the day 1.

What is impressive is the low level shear across southwest WI with a 1km max of 30 knots. Directional shear is also more than sufficient across the risk area.

Based on the ruc's speed shear forecast and the hit the cape took on earlier runs, and the initial 5% tornado forecast... I was going to sit this one out. But I'm a sucker for SPC forecasts so I'm targetting La Cross or Prairie du Chein. These cities are situated on the LLJ, tongue of moisture from the southeast, and most importantly have river crossings.

 

[David Draun]

I'm staying put, but could jog a little north. I'm at NIU sitting at the southern edge of the MDT. I have class until 12:30, but then I may drive up to Rockford and wait for something to pop. Skies are rapidly clearing as the fog lifts, and it is going to be hot and humid today. I think the cap will break sometime around 3-4pm. Good luck to all who will be out today!

 

[cdcollura]

Good day everyone,

Just left STL (took half day) and headed north targeting anywhere from Rockford, IL to Madison, WI near I-39 for starters. This my be cutting it close so the cap can be a good thing if it holds until I get up there. I'm blastin...

 

[Mike Hollingshead]

In Sioux City heading north. I'm having deja vu of August 24 already . Anyway, intersting the 15z ruc now develops convection in sw MN by 21z.

http://www.rap.ucar.edu/weather/model/displayMod.php?var=ruc_sfc_prcp&hours=hr06hr09hr12


The 12z ruc had a nice circulation near there at 0z. Last night's nmm wrf was developing a storm near this area too. So, that is the location I'm currently enroute too.


http://www.wxcaster2.com/CENTRAL_RUC236_SFC_DPTWINDSTRMLINE_06HR.gif

I'd be near or ne of that circulation.

 

[nickgrillo]

I'm thinking somewhere between Mankato and Jackson along I-90 for initiation later this afternoon. Latest surface mesoanalysis shows the warm front extending from the surface circulation (near OFK) eastward across southern MN -- with 1000-2000j/kg SBCAPE existing mainly just south of I-90 at the moment, per RUC mesoanalysis. Continued insolation and moistening/diabatic sfc heating will contribute to increasing SBCAPE and decreasing SBCINH through the afternoon. The 12z MPX sounding shows a very favorable kinematic profile (with ~41kts of 0-6km shear) with RUC mesoanalysis showing 35-40kts of 0-6km shear across much of the warm sector. Low-level vorticity will be maxamized invof the warm front (increasing the liklihood for tornadoes with any sustained supercell structure) around the I-90 region.

I'd stick to the Mankato area as of now (southcentral MN).

 

[Josh Richardson]

I agree with Alex's above post, I am certainly targeting MN. Looks a lot like 8/24 when I chased the Nicollet and LeSeur county TOR. Gonna go with the same plan as well, leaving Mason City here shortly and heading to Blue Earth for data and probably heading north into the Mankato area.

 

[David Draun]

Could everyone's target be a little too far north? Mesoanalysis is showing the highest parameters for storms under a weakening cap near the IA/IL border. There are outflow boundaries from last night present there. I think storms may initiate in that area shortly.

 

[rdale]

TAMDAR soundings have the following 1-2*C inversions capping things off: CID (eastern IA) 900-850mb, ALO 850-800mb, MSP 925-900mb (it's the strongest there, with another weak cap around 775mb)

Central Wisc is also strongly capped around 800-750mb

 

[Robert Balogh]

anyone chasing today

I am in St Paul - anyone gonna head out to try and chase? If so and if interested in company, call 706-207-0227 (yes, it's a Ga area code but I am in Mn)

Sorry if this is posted in the wrong place - I dont post much here and havent even logged in a while due to relocating so might not be familiar with any new rules.

Hope to hear from someone / anyone

Robert

 

[rdale]

Still a healthy cap at 880mb over MSP.

 

[nickgrillo]

RUC mesoanalysis shows the environment across southcentral and southeast MN continuing to destabilize with 2000-3000 SBCAPE and dramatically weakening SBCINH south of the effective warm front -- which has drifted northward slightly in the past couple of hours. The strongly backed surface flow north of the front is providing very strong low-level shear profiles, but this is mostly seperated from the best instability. Deeplayer shear has also increased to +45-50kts across much of the area, increasing the risk for sustained supercell structures capable of producing very large hail and tornadoes should they ingest the rich low-level vorticity surrounding the warm front.

LCLs are relatively-"doable" along and north of the warm front, but raise much higher as you go further south of I-90 (where DCAPE and steepening low-level lapse rates will be more supportive of damaging sfc gusts). I'd continue to stay in my target area of Mankato and play the waiting game. I think we can see rapid supercell development within the next couple of hours if low-level convergence provides ascent along the warm front.

(5:45pm) EDIT: The latest MPX sounding still shows considerable CINH (using both surface-based and mean-layer parcels) but increasing deep-layer convergence/theta-e convergence near the front may be locally strong enough to breach the capping inversion and release boundary layer air (along with continued low-level heating).

 

[rdale]

Last MSP flight still notably capped at 875mb and again at 775mb

 

[cdcollura]

Good day,

Looks like a major cap here, sitting just SE of Le Crosse, WI debating what will happen. No cu field, clear skies, ESE winds, does not take a rocket scientist to see a strong cap is right over me ;-)