8/5/06 FCST MN/SD/NE/IA/ND

[Mike Hollingshead]

Pretty nice looking summer setup for Saturday in the northern plains/midwest. New nam wants a 998 sfc low in sw MN by 0z with plenty of moisture and instability in place, with a 40-50 knot wnw-w-wsw mid-level jet above. It's been fairly consistent in the strength of the system the last couple runs so hopefully this doesn't go down hill any(it is 06 afterall). One thing that should be a bit different than the last couple systems around here is the 500mb temps should be a bit cooler(-8c this go around). The low level jet is plenty strong with this system as well and adds to the rather strong helicity values.

http://www.wxcaster2.com/CENTRAL_ETA_SVR_C...HSWEAT_48HR.gif

I imagine tail-end-charlie could be in eastern SD or sw MN. Hell it could be further south than that, but the 700 temps look like they could cap it off pretty quickly south of that area. All I know is that is a pretty sweet environment for a tail-end-charlie if it is that far north.

Looking around at forecast soundings the convective temps are again way up there.

ScottO, you ready or what? My current target is Brookings.

EDIT: GFS remains slower with the system, and especially the sfc features. It's also a bit more north.

 

[Justin Turcotte]

Potential exists for a significant severe weather event. Parmeters for sig severe look quite high. This looks like one of the better set-ups in the Northern Plains thus far this season (which really isn't saying much given the circumstances but it does look good). I'm writing the details based on low-res web graphics and will have access to the hi-res good stuff including Canadian GEM when I get back to the office Sat morning for the usually ill-timed day shift with sig severe pending. Mixed layer will advect in ahead of the potent trough which will be rapidly advancing through the Dakotas. This strong trough should easily bust the cap during the afternoon allowing for a good show during daylight hours. The difference between this set-up and the warm front bust set-up last week is this one actually has shortwave for lift. There was not one to be found last week when SPC put the MOD out for the ND/SD/MN border area. Shear parameters look downright facinating Saturday afternoon and evening. Solid southerly surface flow, ssw LLJ, rock solid H50 westerly punch with a big fat vort max to give the atmoshere a kick in the ass. Best moisture in sw MN, best lift in nw MN. Perhaps something for everyone. There is usually a monkey wrench in any severe forecast and in this case will be the potential for some solid storms during the AM hours Sat morning in northern MN. There could be an outflow boundary to play with somewhere. Perhaps some supercells during the afternoon before a big MCS brews later on. I may not have to travel far Saturday afternoon with initial thoughts of Crookston, MN around 4pm. Pesky 8-4 shift may require some tweaking. Expecting SPC to go MODERATE with the next SWODY2.

 

[Scott Olson]

Hey Mike, im ready . Im just starting to get a good look at the GFS, as it appears that the NAM is having trouble with frontal timing and precipitation movement. (as noted by MPX & HPC). Most everything looks pretty good, with 40-45kts of effective shear, 3000-3500 MUCAPE and 150 m2/s2 0-3km SRH over a large area. Based on what i've seen so far i'd still favor a fairly local area somewhere between Watertown-Marshall-Brookings. The possibility of a boundary near these locations that would be important to increase shear (and maybe fire a storm off in advance of the front, ) looks possible. Shear vector looks quite nice and storms firing in E-SD/W MN would generally move into even better kinematic fields. Whether it be tail-end charlie (likely) or an isolated cell. Secondly, im qutie interested in NW MN where storm development appears likely by mid-afternoon with good MLCAPE and strong moisture convergence. Given the wind environment and the good low level shear, it's possible this could intially be a significant storm. Will wait for 0z soundings & models tonight before deciding on a target.

As Justin noted, it looks much more solid with last weeks Moderate. In fact, models 0z anaylsis showed quite substanial ridging had taken place in NE SD.


Hope to see some of you out tommorow.

Scott.

 

[Edward Ballou]

Comparing with your forecasts, my meterological "skills" are failing me with this forecast. I'm seeing some good elements but others that are vexing me. The cap looks fairly decent across the southern end of this - it looks as though it reaches maybe even up to Watertown. Scott mentioned good low level shear, but the model I was looking at didn't have very much, but built up better as you go east into Western IA/MN. DP's look good, right mix of CIN, good middle-high level shear. LCL's bother me a little bit as well. Are we setting up more for gustnadoes? Storm motion begins to slow as it hits the front which is good for me because I hate keeping up with fast moving storms. As for target, I would say anywhere from Manchester/Arlington to Granite Falls.

Anyways, feel free to shoot me down - it's a learning experience. You all are welcome to stop by and pick up on my Wi-Fi, I could open it up to anyone who wants to borrow it.

Be aware that Highway 14 that goes directly through Brookings is still a mess as they're working on it. Take Exit 133 to use the bypass if you're going west. I wouldn't advise using 77 north out of Brookings either as they put down some gravel that gets stuck in tires and could ding windshields pretty easily.

 

[Jayson Prentice]

Ed, what model is it that you are looking at? I guess the NAM has been having some troubles as mentioned above, so I focused on the GFS's run this morning and saw some pretty good things. I think that unless the front slows down a bit, the better threat looks to be extreme eastern SD and then into western MN/IA where the better parameters actually are like you mentioned. Both the NAM/GFS have nice areas of parameters in southwest MN and northwest IA, but the SPC seems to have left them out of the 45% probabilities for now...

As for the capping, that may be a concern with some fairly good inversions over the area. But, given the forecasted instability/lift for the area and support I think that it won't be a big problem and we should have storms by evening over areas of SD/MN/IA and even back into northern NE. Still hard to say right now, but I'm thinking a pretty sound severe weather day is forecasted...

 

[Edward Ballou]

I am looking at the NAM.

 

[Scott Olson]

Comparing with your forecasts, my meterological "skills" are failing me with this forecast. I'm seeing some good elements but others that are vexing me. The cap looks fairly decent across the southern end of this - it looks as though it reaches maybe even up to Watertown. Scott mentioned good low level shear, but the model I was looking at didn't have very much, but built up better as you go east into Western IA/MN. DP's look good, right mix of CIN, good middle-high level shear. LCL's bother me a little bit as well. Are we setting up more for gustnadoes? Storm motion begins to slow as it hits the front which is good for me because I hate keeping up with fast moving storms. As for target, I would say anywhere from Manchester/Arlington to Granite Falls.

Anyways, feel free to shoot me down - it's a learning experience. You all are welcome to stop by and pick up on my Wi-Fi, I could open it up to anyone who wants to borrow it.

Be aware that Highway 14 that goes directly through Brookings is still a mess as they're working on it. Take Exit 133 to use the bypass if you're going west. I wouldn't advise using 77 north out of Brookings either as they put down some gravel that gets stuck in tires and could ding windshields pretty easily.
[/b]

Hi Ed, it's certainly by no means a perfect setup but generally there are some pretty good things setting up. While no particularly environmental condition is extreme, most if not all of them appear to pretty good. Low level shear (which will be much clearer tommorow with the possibility of OFB's) is decent across the area and effective SRH is in the 40-45kt range and as high as 50kts farther north. These conditions should generally be favorable for updraft rotation which would allow a right moving supercell to ingest even more helicity. The instability is pretty strong and LCL's while not perfect, appear to be within range for possible tornadoes (though a bit on the high end). The CAP should be overcome with continued surface heating, moisture convergence and lift along the front, hence the high probabilities from SPC. Ed take a look HERE, the area from just north of Watertown all the way into Minnesota shows little and neglibile amounts of CINH by 0z.

For what it's worth, the 18z NAM now shows convection forming around 21z near Aberdeen and moving into WC MN by 0z, into an increasingly sheared environment (200-350 m2/s2 0-3km SRH).

UPDATE: Okay, so the 0z data is now in. No major changes from 18z, with the same sort of convective scenario forecasted. It backed down on the 0-6km shear for NE SD, progging it at 35kts however it still shows 40-45kts for most of Minnesota. Ideally, anywhere within 40miles of each side of the SD/MN border. As storms would have the best of both worlds. The highest axis of instability and increasing shear as it moves to the ESE (right-mover). The NAM has convection over parts of IA/MN at 18z so will definately watching to see if there is an OFB tommorow. Tdd's should be between 15-20 degrees, which is okay by 2006 standards. Most likely will be targetting NE SD. Im not to worried about ending up on a line segment while isolated supercells form further south, given the fact that intiation will be largely from frontal forcing, moisture convergence and continued surface heating (as opposed to having that strong vort max 300 miles south). Though, this could change depending on how the morning plays out.

 

[Bill Schintler]

Chase target:

Montevideo, MN.

Timing:

Surface-based storms initiating at 5 PM CDT.

Comments:

Supercell storms between 6 PM and 8 PM with a chance for a tornado or two where storm-scale boundary interactions occur. By mid-evening, storms will evolve into a large, linear MCS which will track across MN.

Discussion:

00Z charts show zonal UA flow on top of CNTRL/ERN CONUS ridge with several shortwaves embedded within this flow. The first of these is associated with ongoing MCS’s in SD and ND. 00Z WRF SFC temperatures initialized 2-3 degrees too warm over much of MN while dew points generally initialized well with the exception of NERN IA where the WRF was 5 degrees too high. 35kt H85 streak in WRN MN was resolved and is in agreement with 00Z Lakewood profiler data, while the location of the 18Z isotherm and moisture except for moist feed in NE which was 2C too high with dew point. H7 8C through 12C isotherms initialized however 37kt streak in NE/KS is too strong. Regarding QPF, this model does not have a handle on SD MCS and perhaps is overdoing forecasted morning elevated convection in NWRN IA and SWRN MN in association with H85 WAA.

The wildcard in the FCST are where early convection and attendant OFB’s occur. It appears as though a large area of elevated convection will track through SWRN MN early in the period which should lay out one or more OFB’s. This boundary(s) should then drift NEWRD towards an Estherville, IA to Marshall, MN to Milbank, SD line by mid afternoon. Cloud cover will be slow to exit the area to the east resulting in strong differential heating, and the region will remain strongly capped until late afternoon when very strong forcing and UVM in association with 40kt H7/50kt H5 streaks and attendant mid-level cooling. The most favorable target location would then be near the triple-point of the OFB and the synoptic CF, along the NRN extent of the richest SFC moisture. MLCAPE’s to 3500J/kg and good mid-level lapse rates of 8C/km (south) to 8.5C/km (north) will couple with 50 kts of deep-layer shear along with good hodograph curvatures just to the NE of the aforementioned OFB where cloud-base heights will be in the 1000m AGL range.

- bill

 

[Edward Ballou]

Great instability but definite cap & high CIN in the latest run of the NAM. Low level shear improving though. LCL's have dramatically improved. Brookings is looking much better although I think more north is better to get away from the cap. Then as it progresses and the cap breaks down, it will open the chances for a tail-end charlie tornado. See you all out there tomorrow!

Scott & I should arrange a grill party tomorrow for lunch


EDIT (9:39 AM): Going west on that nudge of CAPE is tempting, but all the parameters aren't as good until you get east of the SD/MN line. Marshall & Pipestone's Skew-T's look really good. As of right now, I'll probably head north and east into MN.

 

[Aaron Kennedy]

The good news is I'm now in GFK, North Dakota. The bad news is I have little in the way of chase supplies unpacked other than my camera gear. I'm going to run to the bookstore and pick up a delorme MN/ND map in a bit. Then I should be good to go. WE're closing on a house in a month so we're trying to save some $$$ but I can't deny myself a relatively short chase.

Forecast: This is another one of those trade off scenarios where the best surface winds are down near E SD/MN, however, upper winds are much more condusive for sups in N. ND. My current hope is that WRF is too fast with the front... and winds will veer less before sunset in this region. Otherwise, I'll probably just keep dropping down I29 until I get into a favorable flow at the sfc. I'll probably confine myself to ND/MN.

Aaron

 

[Ryan Pfannkuch]

Gonna have to sit this one out...sure enough I made a RARE previous committment about a month ago and of course it happens to be today <_<

Anyway, thought I would throw out my 4-county virtual target area before I literally start driving AWAY from the risk area. I know if I were chasing I would be hanging around the southern end of the more favorable shear in east-central SD/western MN. To keep it simple and not over-analyze this close to the event, per 15z RUC, I am going to go with the area right along the sfc boundary that intersects the 12C line at 700mb and the 30-35kt isotach at 500mb but favor staying a little east east because the low-level shear looks better to me over western MN especially after 0z. I'm going to straddle the SD/MN border with my 4-county area and go with Grant, Deuel in SD and Yellow Medicine, Lac Qui Parle in MN. This is the area just east of but not including Watertown SD. Best of luck to all heading out today...

 

[Brian Stertz]

Looks like that area from SE North Dakota into NE South Dakota and WC Minnesota is starting to setup and is my bullseye for later this afternoon/evening. Got good strong instability building over much of C. South Dakota. This is beginning to build northeastward into the bullseye area which should have some pretty healthy supercells after 5pm. 0-3km helicity is more favored south of I-90 so sustained tornado potential probably is not as high as it could be. Cap once again a factor along/south of the I-90 corridor so this may not go until after dark. Best of luck to all up in that area.

 

[Doug_Kiesling]

Looks like that area from SE North Dakota into NE South Dakota and WC Minnesota is starting to setup and is my bullseye for later this afternoon/evening. Got good strong instability building over much of C. South Dakota. This is beginning to build northeastward into the bullseye area which should have some pretty healthy supercells after 5pm. 0-3km helicity is more favored south of I-90 so sustained tornado potential probably is not as high as it could be. Cap once again a factor along/south of the I-90 corridor so this may not go until after dark. Best of luck to all up in that area.
[/b]

Currently sitting between Marshall, Watertown and Montevideo on the board of MN and SD. Not much happening yet but I do have a small shower right now. debating to hang here or not. I still looks like it has a chance today.