7/14/2010 FCST: MN/IA/WI

[Andrew Pritchard]

The terrain is going to be a big bummer on this one, and the vast differences on main operational models are also a bit troubling. Anything south of the MN/IA border should be linear pretty quickly. Given extreme instability and unseasonably strong flow, a tornado can't be ruled out in Iowa, but I think it would be a fairly isolated and embedded event given more veered flow in this area.

While it's a fairly wide target, I do see a region that does stand a chance at a localized tornado event tomorrow assuming the NAM and WRF are correct. My somewhat large target box would be along a Minneapolis to Rochester line, and then east to a Tomah to Eau Claire WI line. In that region, I'd really favor the northern extent of that box as well. I guess more specifically I think the best chance at a significant tornado is along that Minneapolis to Eau Claire line. Chasing that area of Wisconsin would be a real treat, so one's best hope is probably to try and get something early before things get into the god awful terrain near the Mississippi river in far eastern Minnesota. I think anything significant should be along and north of Interstate 90.

Eventually training/congealing will likely lead to congealment into an MCS. If I didn't have plans here in northern IL til mid-afternoon I would probably venture out to far E-SE Minnesota (Faribault, MN - if I had to pick a target city) just to get in a nice July chase, but this will probably save me some frustration. I just think the terrain on this one will be a bigger day ruiner than the actual setup itself.

Now if you're siding with the GFS, tomorrow looks like an absolute wash. No surface flow, and completely unidirectional flow above that. With all that instability and no real directional or speed shear, you'll end up with a big multi-cell cluster that does a whole lot of gusting out. I think the NAM solution is a little more likely, but it's something to keep in mind tomorrow.

I guess I'll just hope that something fires inexplicably in southern WI or NW IL that I can play with.

 

[Scott Weberpal]

Based on tonight's NAM, I agree 100% with Pritchard. Backed surface flow essential within the driftless area should yield a decent chance at a few tornadoes from the twin cities to Eau Claire to Tomah to Rochester early, and a relatively quick transition to linear mode before nightfall.

I put little faith in the GFS within 24 hours, in fact, I've never looked at it inside of 84 hours. I just can't get myself to look at a lower-resolution global model over a much higher resolution model. Just looking at current observations and location/strength of the upper trof, it's looks apparent that surface features should respond nicely tomorrow. IF the GFS does come to fruition, I'll be in the flat lake bed of glacial lake Wisconsin in the central part of the state.

FWIW, the 4km WRF initiates a couple supercells just south of the twin cities and essentially moves them along or just west of the Mississippi River...that would be fun......not.

 

[Derek Weston]

Some impressive hodographs in west central WI by 21z. According to the NAM, Minnesota is pretty much shut off by 21z and action ought to be going east of the Mississippi. Interesting that the corridor of good CAPE doesn't extend too far east into WI... could be a limiting factor. Certainly a potent combination of ingredients. 15% hatched seems warranted.

Further SW . . . NE Iowa looks interesting to me. Charles City and points immediately north and east... again, nice looking hodographs and quite a bit of juice to work with. Don't see why this area would tend to favor linear development anymore than north... and considering the terrain, would probably be my play.

 

[MattKaskavitch]

I think my play will be south. Initial target is near Austin, MN, however that may be adjusted come morning. Hodographs are looking good and the terrain is much better south.

I live directly in the middle of the 15% TOR hatch area. The terrain here is down right dangerous for chasing/spotting. I'd advise anyone to be particularly careful if venturing here. There are many rolling bluffs for at least 70-80 miles into Wisconsin off the Croix river and Mississippi.

My prayers will be long tonight, going to be tough not being home when the forecast is such here. We all love a nice TOR in an open field, but this hatch is near some very populated regions and one that I call home.

Stay safe everyone.

 

[Zach Young]

For what it's worth, 4km WRF doesn't break out precip, I don't think.

It should be worth noting that the 4km WRF is initialized at 00Z, but its output on the NSSL page updates one image at a time with each new image replacing the one from the previous day. The output doesn't reach the afternoon hours of the next day until ~06-07Z from what I've noticed (about that time is when the 24hr+ graphics are up). If you look at the output too early, the later images are actually from the day before.

Looking at the 4km WRF right now, convection initiates by 01Z in the Twin Cities area, and rapidly grows upscale. There may be a window for tornadoes for a few hours before the whole thing becomes one giant squall line. Which model will be right? Is it the one behind door #2?

I can't get out that far though, so I wish everyone luck! May you catch giant tornadoes, and may they avoid all the houses.

 

[Rob H]

I hope this is okay for this thread: Be aware of numerous construction projects taking place in the Twin Cities metro (and greater metro) area. I would advise avoiding the entire area at all costs. I've personally seen the traffic mayhem that occurs in "bad weather". Also, another choke point that may come into play: the St. Croix River/Mississippi River (WI/MN border).

http://hb.511mn.org/main.jsf is the construction map for Minnesota. 90 has some horrible one-way alternating traffic, and I35 (which splits into 35w and 35e) has "critical disruptions". Even without construction, anytime after 2pm you will possibly hit stop and go traffic in the metro area. If you're not familiar with the Twin Cities, I'd strongly recommend staying out of the "circle" that 694 and 494 create around the metro. The river crossing in Cottage Grove and Stillwater will likely be frustrating so give yourself an extra 15 minutes to cross those.

That being said, I don't have any confidence in the GFS when it's less than 84 hours out. I saw some amazing moisture advection late last night while standing in my backyard that really underscored how much juice this system has to play with and it looks like yesterday's activity won't disrupt today in the target area. I especially like that winds are backing more in E MN than they were on previous runs. I'm a little concerned with the lack of cap strength - I'm one of those guys that prefers it to be stout enough to keep things from being messy. I don't think it will have a hard time being broken at all, I'm more worried about this turning into a massive bow or possibly even derecho. I can't recall the last time I've seen UA troughs, with the jet that fast, in the middle of July in MN.

I don't think we'll be heading further south than Rochester today, and I'm liking Red Wing at the moment. It's close to the metro, but far enough away that traffic won't be as much of an issue.

 

[Bart_Comstock]

HRRR and 4km both show a somewhat similar scenario with the storms lined out by 0z. The HRRR leaves a slightly more favorable setup with cells going up very early (20z) and staying a bit more discrete before becoming a long line. I imagine once the storms line out we will still see several vigorous LEWP's that will pose a serious risk of rain wrapped tornadoes. This setup looks like it will be a tornado producer but as to how photogenic and how visible said tornadoes will be is something that would concern me greatly if I was chasing. Besides the SPC went on ahead and put out a 15% hatched area so you know it has to be a bust now.

The SPC has thrown a 60% area up for wind damage and that looks justified as one heck of a squall line should emerge from the rapid upscale growth of the cells that will form today. It will be interesting to see how today plays out and just how chaseable this set up will actually be.

 

[Mike Hollingshead]

Maybe more of an observation at the moment than a forecast, but wow is there some juice and heat out there. The 10 a.m. obs are quite impressive. 90/81 in Red Oak Iowa. Seems every other ob in the area is 88/79. The corn went nuts pretty early this year and is probably 10 feet out there already lol. Not that one needs more moisture via evapotranspiration. That is just crazy for 10 a.m.

The rest has already been hashed out. Too bad for the small favorable area moving into a bad area and kinda veering out the later in the day one gets. If I lived closer to the area I'd for sure be out. After 900 miles yesterday just can't say I'm eager to venture up there for the better play area today. Cold front might be interesting at least early on, like perhaps a nice intense cg barrage as storms first fire in this heat.

Out of boredom I thought I'd try and find the most funny forecast sounding as far as cape. Looked at a 6hr and 12hr cape image off rap and MCW in northern IA seemed it would work for a 21z try/look.

MCW It did LOL. If only we could take half that 9500 cape off there and tuck it away for some April chase next year. Yesterday while in ND I asked myself, "Is it really July"...it felt so relatively cool while under sun. I guess it is indeed July.

 

[Jeff Duda]

It should be worth noting that the 4km WRF is initialized at 00Z, but its output on the NSSL page updates one image at a time with each new image replacing the one from the previous day. The output doesn't reach the afternoon hours of the next day until ~06-07Z from what I've noticed (about that time is when the 24hr+ graphics are up). If you look at the output too early, the later images are actually from the day before.

Mike, that surface parcel has a theta-e of over 390K! You rarely see such a high value.

Zach,
Both NSSL and NCEP run 4km CONUS runs. NCEP does runs at 12Z and 00Z, while NSSL performs its run only at 00Z. See http://www.emc.ncep.noaa.gov/mmb/mpyle/cent4km/conus/00/ (to get the 12Z run, simply replace "00" with "12" in the URL).

 

[L.B. LaForce]

Looking at the RUC this morning seems to paint Armageddon, although the chase terrain is somewhat disappointing. I expect storms to fire around 20-21z, and then eventually becoming possibly a derecho by 0z. Storms could start NW of MSP which would not be good, but then track SE towards the MN/IA/WI border. 0-1km helicity values of 200+ m^2/s^2 should support rotating supercells as long as they remain discrete. 0-1km EHI values also climb into the 7+ values. High PW values of 2+ inches may also indicate that storms will quickly become HP, reducing visibility even more against tough terrain.

Be on the storms quick-right when they initiate for bet chances of tornadoes. I also picked Owatonna as it was near some "main" roads.

Target: Owatonna, MN

Target polygon:

 

[Greg Blumberg]

I am a little bit concerned for the tornado potential in the target areas. First of all, per the 12z 700 mb map, some very high temperatures are being advected into the target area. This should increase the strength of the EML and cap and help hold of storms. I'm seeing 14 C, 15 C and 11 C temperatures, but considering the strong upper level lift combined with the explosive air currently within the boundary layer...these temperatures should not hold off convection.

http://w1.spc.woc.noaa.gov/exper/soundings/10071412_OBS/MPX.gif

That is quite a sounding at MPX. I'm seeing a very dangerous situation unfolding across the southern MN and WI area.

My thoughts are that near the edge of that warm 700 mb air mass will be the areas for supercells. That way the linear forcing will be far away from influencing the discrete storms.

 

[Dean Baron]

Surface winds are veering across a large part of the target area, with no stations showing backed winds in southeast Minnesota. On top of that cloud cover is limiting heating here in the cities, but looking at obs down in IA I see much better heating. That new MD has me a little confused though. I honestly don't know what to think at this point, I'm starting to lose confidence in today.

 

[Jeff Duda]

Surface winds are veering across a large part of the target area, with no stations showing backed winds in southeast Minnesota. On top of that cloud cover is limiting heating here in the cities, but looking at obs down in IA I see much better heating. That new MD has me a little confused though. I honestly don't know what to think at this point, I'm starting to lose confidence in today.

If you look at 850mb as well as at 700mb, there is a very warm dry punch with axis oriented SW-NE from NC KS through Lincoln and Omaha and up to just west of Mason City to near Albert Lea. This surely will not be a favorable area for convection (under this dry punch). However, just behind that, things cool and moisten significantly, and that's probably where convection will be able to persist for longer. I'm not saying convection won't initiate in the dry punch, but if it does it's going to have a hard time staying alive for long.

 

[Greg Blumberg]

Holy cow. The IA, S MN, and S WI are going to see some wild weather today when things get going. It seems that the corn fields in IA have created some 90ish/80 ish dewpoints. This is surely some explosive air underneath the cap.

I'm willing to be that there will be an 18z sounding within the area from many stations in order to assess the atmosphere's potential for severe weather.