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

Mar 3, 2004
Mt Prospect, IL
Looking at the GFS and ETA models, I notice a deep western trough and a strengthening eastern ridge. Moisture return looks good with a surface low punching into warm, humid air over the midwest. Temps in the 80's and dewpoints in the mid 60's possibly on Tuesday. In fact, Chicago's forecast high is around 80 degrees on that day. Surface winds over the region look to be SSE at this time. I'd like to see stronger upper level winds, but it looks like there is some potential. There could be a few shortwave troughs coming off the main one for multiple events, including the next Thursday Friday timeframe.

I figure it's too early for a narrowed down forecast thread, so lets discuss this here. October can be a good chase month as we all know.:cool:
Yeah I've been kinda watching the GFS around that time too. A few days ago it looked like a weak shortwave would eject into the plains around weds Oct 4th but now it looks like it becomes a cutoff low and doesn't move out until Sat & Sun Oct 7th and 8th which would make it a possible weekend chase. Also gives more time for moisture return to reestablish itself. Keeping an eye on it.
Well you'll be all alone chasing since the student body and loyal Sooner Nation will be in Dallas for OU/TX weekend. These types of events occur frequently during the fall/winter and it seems they are quite slow movers which produce more weather in the form of heavy rain, or linear events due to the backed mid-level flow...I'm going to be patient and wait to see what the winter has to offer in terms of snow in the Rockies to improve the EML from this year...and lighten up the skies in Spring 2007.
This thread cannot be in Weather & Chasing. Keep all chase forecasts thread in the appropriate areas, please.

The GFS usually trends toward more amplification as we move towards the period. However, it is showing easterly winds over the NGOM (high pressure and the front still hasn't retreated back northward), signaling that moisture quality may be a problem.
Just taking a quick look at everything on the ETA and tomorrow looks like it could be a weekday chase in Iowa and Wisconsin. Just have to watch out for the rivers... The Li and Cape look to be worth taking a look at this day as a late season chase.
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Tuesday looks like a pretty good setup for tornadic supercells forming along the warm front across Southern Minnesota eastward into Southern Wisconsin. The shear looks pretty strong...I can see a strong tornado happening. But it will be another tornado day I miss.
No model handles this mornings MCS in the slightest way close to reality, I'd expect another one tonight to form maybe a little more to the south and I think any formation/remnant clouds will play a big role in where & when things happen tomorrow. I like southern WI / northern IL for now, I don't know that MI will still be under the same level of threat by the time the storms get here.
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SPC new 1730 outlook includes southern MN, all of IA, Northern Il, and Southern WI in a slight risk, with a hatched 30% in southern MN and southern WI. This is quite reasonable considering the latest WRF and GFS place the strongest shear and instability over this area. Latest models dont make me worry about a CAP as much as I did with the earlier runs. The same is true in regards to moisture return. GFS and ETA still vary signifiacantly from each other on both the timing and the instabilty in place. Only place that they can come close to really agreeing on is in and near the 30 percent risk area. NCEP SREF also follows this very closely. Shear profiles appear to become more favorable for supercell structures by afternoon. Forecast storm motions, would suggest east moving supercells, which would aid in maximizing low level shear. Guess we will have to wait for some new models, and see if they can come together.

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I'm betting towards southern MN for a good shot at tornadic supercells tomorrow afternoon, where low-level shear and low-level streamwise vorticity will be maxamized along the sfc warm front. All models seem to be in agreement with rich boundary layer moisture streaming into the warm sector by tomorrow afternoon -- and in associated with sfc diabatic heating -- will yield modest sfc-based buoyancy (i.e. SBCAPE >2000j/kg) with considerable capping to a low-level parcel prior to 21z across much of the area. With strong mid-level PVA and low-level convergence, I wouldn't worry about capping across southern MN tomorrow. I'm thinking initiation will occur near the front by 3-5pm.
I'm favoring the area a bit further east into WI where the H85 flow is forecast to be stronger. I just hope storms fire east of I-94, western WI is one of the last places I'd like to chase...very comparable to areas of the Ozarks.
This looks to be quite an interesting event for SE Minnesota and S/SW Wisconsin, considering the date. The 00Z semi-unreliable WRF run depicts a strong warm front from near Mankato, MN ESE along I-94 through Tomah, WI, and eventually towards Milwaukee/Kenosha (a tad farther south than previous runs). With a strong easterly component to surface winds near the front and an increasing southwesterly LLJ poking its nose into southern Wisconsin by tomorrow evening, supercells seem likely. Moisture will be ample (Tds in the mid 60s in October....sweet....) and there should be good clearing throughout the morning and early afternoon to allow destabilization.

Based on the WRF, I guess I'd look for convective initiation (hopefully surface-based for whoever's chasing) to be somewhere near a line from Rochester, MN-Winona, MN-Tomah, WI....but the latest GFS depicts the warm front slightly farther north.

My plan is to stay in Madison, WI and wait until early to mid afternoon and look for good boundaries, etc., for a potential local chase. Good luck to whoever's heading out!
Chase target for October 3

Chase target:
Windom, MN (25 mi NE of Worthington).

Initial storm initiation will be between Sioux Falls and Watertown at 3 PM. Storms will quickly develop to the east into an environment with best moisture and low-level hodographs. Expect one or more supercell storms in the target area between 4:30 and 5 PM CDT. Hail to golf-ball size will be the primary severe threat, however an isolated tornado cannot be ruled out, especially where favorable storm-scale interactions occur.

00Z analysis indicates a ridge axis over the Dakotas and a potent wave over the Great Lakes which caused a variety of severe WX in WI/IL/OH today. Over the WRN CONUS, a strong S/WV over ID is embedded within a broad ULVL trough. A 30kt LLJ is nosing into IL while transporting a plume of 14C air mass into the Great Lakes. At the SFC, a disorganized area of low-pressure is centered over ERN NE while dewpoints have climbed into the mid-60’s over IA.

The WRF has initialized well to SFC dewpoints and temperatures over much of the Upper-Midwest, and this model also has a good handle on the H5 speed max lifting into WY. By early afternoon today, the WRF develops several H5 speed maxes within the SWRLY flow: the first one will be translating towards Lake Superior while a second compact wave should be over SERN SD. The GFS has initialized weaker with the H5 max however it too moves a compact wave towards SD/MN by early afternoon. It also initialized slightly low with SFC moisture and temperatures. The (12hr old) UKMET solution is about 6 hours slower then the other models with the evolution of SFC features. In addition, the low is a weaker solution which is more of a wave along the CF. The NGM solution is very similar to the WRF with regard to the low track and evolution of S/WVs within H5 flow. The overall model consensus is weak with regard to SFC and H85 flow and convergence, however given the strength of the mid-level wave, the SFC/H85 system should verify stronger then models suggest.

Modest instability, with MLCAPE’s approaching 1500 J/kg, will couple with seasonably impressive shear parameters. Deep-layer shear should approach 60kts under the aforementioned H5 S/WV while (SFC-3km) hodographs will locally approach 300m2/s2. A potential concern is the extent to which a push of dry air at 850mb works north and east towards SWRN MN.


12:05 AM CDT
I'm about to take off from Mt. Lake MN. Looks like it's going to be a great day for a traveling/chasing day. Just looked at the spc and Interstate 90 and 94 eastbound are in their target zone. This is going to be a good day.
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.
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.
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.
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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!
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...
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.


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.


I'd be near or ne of that circulation.
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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).
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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.
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.
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