06/17/10 FCST: SD/ND/MN/IA/MO

[Chris Wilburn]

I agree this looks like a fairly impressive setup. I would try and pick a spot where the winds back more at the surface. This looks to be the case at the previously mentioned SD/ND/MN border area. I would play anywhere from Fargo to Brookings. Any possibly outflow boundaries will have to be examined in the afternoon as well. Fairly impressive directional shear and speed shear profiles showing up on the hodographs for south of Fargo. Impressive 0-1 SRH values near 200 in this area as well. Everything looks good in regards to all the parameters. CAPE an moisture are obviously not a problem. Wind shear looks very nice as well, esp. in the northern half of the 10% area. Looking at the 4km WRF it appears things may be somewhat linear with embedded supercells. Initiation may be as early as 3pm according to this model. The CAP won't be an issue so that's a plus for those heading out. According to bunkers it appears storms will be pushing 40kts towards the northern half of the 10% area. Storms speeds decrease the further south you go. This may cause some problems keeping up with storms. I guess that's always one of the drawbacks when you have such a strong trough.

A secondary area I would keep an eye on is eastern Nebraska into extreme western Iowa. The surface winds don't back as much here. They are almost due south in this location, but the 500 mb winds are forecasted to be almost due west here which will help with increasing directional shear. Still 0-1 SRH values are lower in this area. Also, LCL heights will be higher in this are as well in the 1,500 range. The CAPE in this area is much more than the northern half of the 10% so there is an advantage there.

I would target south of Fargo where the surface winds back more. I wouldn't be surprised to see something happen in eastern Nebraska or western Iowa, esp. if the winds could back even just a little bit. I definitely wouldn't be surprised to see western MN with several tornado reports later this afternoon into evening. I think a significant tornado threat is also possible in areas where the surface winds will back more.

 

[Edward Ballou]

Since I started chasing, I haven't seen much build up over Brookings. Usually it starts up east of there. I might suggest Lake Benton, but I like the Pipestone to Worthington area the best. It might develop later, but the rewards might be good. The CAP seems to linger over Brookings but breaks down between the 18-24z over the Worthington area. NWS FSD is stating 4 pm and SW MN which sort of validates my forecast. I don't know if I'll be able to make it that far south and east. I'll probably end up east of Lake Benton as it offers a higher elevation for viewing.

In general interest, I'll be watching the ND/MN border as well - I think that is a good northern option.

 

[Dave Winslow]

SW MN/NW IA

Due to my location in Sioux City, I am biased to choose NW Iowa and Southern MN as target areas. The front looks to be moving at a pretty good clip and RUC confirms this as it shows the cold front near Sheldon to Worthington by 4 pm. Also pretty excited about dew points of 74-75, which seems likely with 5" of June rain so far and knee high corn. I would say the MN/IA border in this area you'll still get some good low level shear if surface winds don't veer too much as the front approaches. Storm motion won't be too bad, and roads are great. I won't have any radar data if I go, but feel that the good visibility and road networks will make it doable with some phone guidance. Will be readjusting by lunch time.
Dave

 

[Greg Blumberg]

Waking up this morning to check the obs...I am not disappointed by what I see, however some moderately strong capping does exist. I was going to mention "think south" last night, but decided against it since I wasn't sure about the advance of the 500 mb trough. If this wasn't such a well put together system, I would be concerned about the capping, but I can see some discrete supercell storms firing off in this environment sometime in the evening. The plus is that we just keep on getting that good Theta-E advection coming into the area to help break the cap.

NCEP has also identified boundaries galore at 9z (link is time sensitive till tomorrow):

http://www.hpc.ncep.noaa.gov/sfc/lrgnamsfc09wbg.gif

I can already see the jet punching eastward from the WV imagery. I would not be surprised to hear of cyclic supercells and some tornadoes in MN today. Some of the shear values I'm seeing from this morning's soundings (OAX and ABR) are very interesting...the low level shear looks very good for tornadoes, and I'd expect that to increase over time.

http://w1.spc.woc.noaa.gov/exper/soundings/10061712_OBS/ABR.gif

http://w1.spc.woc.noaa.gov/exper/soundings/10061712_OBS/OAX.gif

I'll forecast SPC for the hell of it...I think they might go High Risk for this one considering the way things are shaping up.

 

[Kyle Masters]

Looks like I chose a good day to burst back into storm chasing. Finally back from my deployment with the army, and the weather gods have given me one so close to home!

I'm looking at models, and looking like, as usual, initiation will take place in the I-29 corridor from Omaha pretty much up to Canada.

Looks like I'll be putting her in park in Brookings, SD and waiting to see whether to go north, south, or east from there.

 

[J Trueblood]

I am actually fairly surprised to see SPC putting the tornado risk where it is. The deep shear is available all over the MDT risk area, but the only low level shear is further north. As mentioned before, it looks like central Iowa could have a capping problem. Anytime I see 5000 CAPE in Iowa I start to get suspicious. Judging by the pretty good low level shear, being on the nose of the jet, high dewpoints, a bullseye of EHI, and a good amount of instability, I'd say the tornado probability needs to be pushed further north. I'd look in a general area around Fargo. Also, given the high cape values, if anything goes up and can stay discrete, I'd look in the sanborne/worthington maybe a little east more areas of the Iowa/MN border for something. But who knows, I'm new at this so we'll see.

 

[J West]

I'm not much of a pre-event forecaster, but based on a quick look at the situation I'd plan a target somewhere east of Brookings, while staying in MN...perhaps between Brookings and Redwood Falls. Any one of the existing boundaries that seem to draped across the area will help a storm that fires along it. Iowa will fire up first, but I fear those storms will congeal fairly fast and just be prolific rain makers. I agree with others that the northern option across SD/ND/MN seems to the better bet.

Edit: I thought about blowing out of here (MKE) and heading west, but with a 7+ hour ride to get in position, I wrote this one off. Maybe tomorrow.

 

[J Trueblood]

Interesting..the 13z RUC now is showing good shear in NW Iowa..Maybe the SPC was right afterall. Who would have thought?

 

[AndyGabrielson]

I remember the thread about areas that were "due" for significant severe weather. Spending virtually all of my life as a child and adult in Luverne, MN I knew that area would come up... Well here we are today and the situation is setting up pretty nicely for tornadoes across west central/south west Minnesota and into north west Iowa. I'm not too concerned about the cap as someone mentioned earlier. Watch for initiation along and probably just west of I-29... the best instability appears to be just across into Minnesota/Iowa east of I-29 storms will probably go insane as they get to HWY75... Supercells should sustain themselves and be somewhat isolated at least as far east as a Montevideo - Jackson - Spencer (IA) line... at some point though this will likely turn into a large line (some embedded supercells)... should be fun, best of luck to everyone chasing today...

Target: Currie, MN

 

[Mikey Gribble]

Interesting..the 13z RUC now is showing good shear in NW Iowa..Maybe the SPC was right afterall. Who would have thought?

The shear was good in NW Iowa and SW Minnesota with the models yesterday too. In fact I don't really see any difference at all with the low level shear environment from yesterdays runs to todays. SR winds in the 5-10km range aren't good anywhere, but they are particularly bad over Iowa and improve as you go north. Forecast hodographs over the SW portion of Minnesota were better (going off yesterdays runs because I haven't seen them yet today), with more like 25kts at 10km SR. The top half of hodographs still weren't impressive, but over the southwest portion of Minnesota they are closer to what you'd expect to see with a typical tornadic supercell environment.

I thought SPC was dead nuts on with their tornado probability, both with placement and the extent of a tornado threat (10% hatched). The best area to me looks like the southwest portion of Minnesota. They centered the tornado prob right on that and probably extended it either way a tad just for overlap purposes.
Farther north there is too much forcing and not enough instability. Farther south the mid and upper portions of the shear profile degrades. The best overlap of favorable thermodynamics, shear and likely convective mode is right there over southwest Minnesota where they centered the tornado probability.

 

[Nick Hartley]

After sleeping on it, I think I'd push my target east toward Revere, Minnesota. However, I do think the best chance for tornadoes is between I-29 and US-59 in Minnesota. Would like to leave Brookings around 2:30 and head to Lake Benton to refine the forecast. I think the front will be through SD by about 22-23z and the Buffalo Ridge should help with any storm formation.

After saying that, and with my transmission slowly going out. I'll probably stay within the Brookings area and hitchhike to chase the storms

 

[Dean Baron]

I dont like the VWP's on the forecast soundings in sw MN. Gonna stick to west central MN right along the SD border for initiation where surface winds are forecast to be backed more. Instability won't be as high up here farther to the north, but it should still be plenty.It'll be tough chasing as these things will probably be HP beasts considering the 70+ dews for parts of the area.

 

[Nick Hartley]

First tornado watch is likely within the next hour over eastern SD. Cold front showing up nicely on the visible sat. May head west to Arlington to wait and see, with the cloud deck filling in here.

 

[Mikey Gribble]

I'll just copy and paste from my blog. I'm going to try to post regular updates today since I plan on watching this one unfold, so here is the link if you're interested http://loadedgunchasing.com/blog1/

Here is the picture and post from my blog...



Everything seems to be coming together nicely for a few tornadic supercells over potions of Minnesota and Iowa later this afternoon. Cold front is clearly showing up on satellite now as you can see in the above satellite picture. Storms should develop along the boundary later today.
Forcing is too strong over northern portions of the target area and convection will likely go linear too quickly, mitigating the tornado threat to a large degree. Farther south along the South Dakota/Minnesota border area convection should be a little more discrete with broken line/clusters and discrete supercells being the primary mode of convection before merging downstream later in the day. Because of that more favorable convective mode and the good overlap of CAPE and shear in this same area, that is where the greatest tornado threat will develop later today.
There are several things that bother me a bit with this setup, but no major concerns. SR winds in the mid and upper levels are better today than previously forecast by the models, which definitely helps. Hodographs will be pretty favorable for tornadic supercells all the way from Omaha up into west central Minnesota. Directional shear could be better in the lower portion of the hodograph, but as is 0-1km SRH >100 across the entire area circled above in my map is pretty good for a solid tornado threat.
With the combination of decent deep layer shear and strong to moderate instability the environment will be quite favorable for persistent supercells over the instability axis. Even though a surging cold front will be the initiating boundary, shear vectors normal to the boundary will favor at least semi discrete supercells from Omaha to north of Brookings where the greatest tornado threat is.
There are good paramaters over a large area so I expect to see a fair amount of tornado reports. The conditions are favorable for a few cyclic tornadic supercells with the potential for a strong tornado or two with any discrete storm.
I’d target the Brookings to Sioux Falls area initially and see how storms come off the boundary. Getting on a discrete or tail end storm will be critical. I plan on watching this unfold through the day so I will update regularly.

 

[Chris Campbell]

Tornado watch #334 has just been issued, covering NW Iowa and a large part of western and central Minnesota.