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

[David Draun]

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.

 

[Terry Tyler]

Yup...Moved back to MS, just in time for the severe season...And, here i though the year was over for me...Cant wait.

 

[Verne Carlson]

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.

 

[Adam Atkins]

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.

 

[Tim Vasquez]

This thread cannot be in Weather & Chasing. Keep all chase forecasts thread in the appropriate areas, please.

Tim

 

[Jim Tang]

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.

 

[Doug_Kiesling]

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.

 

[Jim Bishop]

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.

 

[rdale]

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.

 

[Brandon Sullivan]

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.



brandon-kc9iln

 

[nickgrillo]

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.

 

[Scott Weberpal]

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.

 

[Ross Lazear]

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!

 

[Bill Schintler]

Chase target for October 3

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

Timing:
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.

Discussion:
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.


-bill

12:05 AM CDT

 

[Shawn Hiebert]

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.