08/08/09 FCST: NE/SD/MN/WI

[Mark Sefried]

Interesting day appears to be setting up across portions of the upper Midwest. The area that has my interest is Se MN and SPC just upgraded the tornado potential to 10%. The 850/500 mb winds look decent later on today and this evening across Se MN. Cape, LI's, and an ofb left over from this mornings activity is starting to pinpoint a fairly obvious target area a little south of MPX. The cap should not be as much as an issue later today as it was yesterday. If I did not have plans later tonight, I think I would be chasing today. Good luck for everyone that plans on venturing out. There should be some nice sups out there later on along with a few tor's especially across Se MN.

 

[Jeremy Den Hartog]

I will be out and about doing some chasing...

Dew points here in southern Minnesota are now 75-80 with lots of sun. I'm currently in Mankato at work until 3 PM but I'm trying to decide if I want to head west or east. East of course is where the SPC has the 10% chance for tornadoes. West the chase terrain is a little better and there are already tornado warnings in southeast SD. I might just stay put for the time being as Mankato is right on the western edge of the 10% risk but we will see what things look like in a couple hours when I get off of work...

 

[CZandbergen]

A little late to this one but thought my forecast might help those chasing this afternoon.

Target Area:

Lake Wilson, MN

Timing:

20Z

Storm Mode:

All modes of convection are possible with super cell / multi cell favored late afternoon to early evening.

Synopsis:

An upper level ridge is centered over the target area per the 12Z soundings. Winds at 200mb are WSW at ~80kts. There is a surface low centered on KSFD as of 18Z with a warm front extending to the ENE on a line from KSFD to, Redwood falls MN, Glenwood City WI, then to the ESE. There is a trough of low pressure extending from the surface low to the N and extending from the surface low to the SSW according to a 17Z hand analysis.

Discussion:

Convection is ongoing to the W of the target area as of 18Z with one cell already warned to the W of KSFD. The RUC shows very little movement in the surface low over the next 12 hours. The low should continue to slide ENE along the nearly stationary warm front over the target area. The latest RUC runs show a trend to keep surface winds backed through 22Z in SW MN. With CAPE values in excess of 3000Jkg and 0-3km helicity values over 100 the atmosphere is certainly primed for potentially serious convection through the late afternoon and evening hours.

The activity should continue into the evening moving through an environment with sustained shear and an excellent inflow of 70+Td's from the SE. Deep moisture is available with 850mbTd's approaching 70 over southern MN according to the 12Z RUC run. 700mb temps are progged to be in the 12 degree range at 20Z, however given the convection to the west, the trough of low pressure and the warm front, there should be plenty of forcing available to break the cap with CinH values falling to -50 by 21Z.

The only down side I see to this setup is the probability that it will line out into an MCS/MVC later in the evening. However, if cells can remain discrete during the late afternoon and early evening hours this is very chaseable.

Graphics available at my blog. http://ke5zol.blogspot.com/

 

[jamesmseitz]

Sitting in the Tein Cities and waiting..... there seems to be a jump in the moist air in the last hour. Not to sure about the cap..... Seems to want to hang on. We will see. I will be out in about 30 minutes

 

[Jeff Duda]

large region of 13-16C 700 mb temps moving into S MN...doubt there will be any daytime convection there unless that warm air moves out. I think most are sticking to the northern rim of the cap in central MN (as I see on spotter network).

 

[Rocky Rascovich]

Starting to get concerned over just how this severe weather scenario will pan out. The supercell that was north of YKN a couple of hours ago is toast, probably ingested alot of dry air in the 600-700mb. levels, the supercell that was just north of FSD around 1930Z has fizzled as well and has left what I think is a pool of subsidence as alot of the bubbling Cu that was across southern MN. along the Hwy 169 corridor has cleared out. There is a thin overcast due to the anvil blowoff in this area. What I'm also concerned about is that winds are gradually veering so low level helicity values are hardly adequate. Low level flow west of I-35 and south of Hwy 212 is negligible, but east of I-35, you still have a fairly decent flow out of about 170-180deg@15-20kts. All this according to SPC's mesoanalysis page and surface ob's. There is monster surface cape (near 5000 j/kg).. with dews approaching near 80 at several sites.

The vortmax is currently a little east of RWF moving ENE, as lift increases, CINH should (and almost already has) been eliminated and CI should initiate within two hours of this post. Still I think svr parameters should be met with best chances along Hwy 14 on north to an area along and east of STC to about 30mi. N of MSP . I'm beginning to have my doubts about this being a big tornado day, but a stray one is not out of the question. Biggest threat will be hail and damaging winds especially into western WI. after sundown and maybe then into SE MN. around AUM where my mother in law lives, I'm sure she'll be calling me for updates.