2014-09-03 FCST: MN

[Mike Marz]

I feel like this may end up being Minnesota's most active tornado day this season (which isn't saying much) as we get a nice warm front set up right along I94. The middle part of this week has been looking interesting on the models for about a week now, with decent 500 winds all across MN, a pretty good low level jet that kicks up in the evening, and good CAPE along and south of the warm front. Hodographs in central MN have a pretty nice shape http://www.twisterdata.com/index.ph...iew=large&archive=false&sounding=y&sndclick=y and the models do show storms firing along the front. I think supercells might explode around 5-7pm near or west of St. Cloud in the wake of early day storms. If this happens and the updrafts are able to get to the surface instability that is forecast, it could get pretty interesting. Definitely interesting enough for September 3rd. I was hoping this morning that the SPC would upgrade the slight to 30%, maybe 30 hatch, and was happy to see that they did at the 1230. Unless a Wayne type event happens later in Sept or early Oct like last year, I think this could be the last chase of 2014. : ( Hopefully it turns out to be somewhat decent. (I'm still very new to forecasting so hopefully smarter minds can tell me I'm either somewhat right, or just wishcasting...)

 

[Skip Talbot]

My main concern with this setup is getting surface based storms. With slight height rises and lack of large scale forcing besides warm air advection on the warm front, you're probably not going to see initiation in the warm sector except perhaps right on the boundary. Everything else is going to fire north of the warm front where you're forecast to get ongoing elevated convection all day.

NAM was hinting at it last night, but the HRRR is plotting discrete storms riding southeast down I-94 orientated warm front. These cells looks like they're well north of the boundary though.

That looks pretty good. A nice discrete storm in the target area.

Until you realize where that storm is relative to the boundary. The white spot on this cape plot marks the cell's location, and you can see it's tracking through 250-500 SBCAPE, well off the boundary. The RAP was plotting 1500 MUCAPE north of the warm front, but the SBCAPE drops off sharply right on the boundary as it looks like it's going to be convectively reinforced by a big cold pool. I think you could definitely see some supercells with big hail up there, but they're going to be elevated storms. If something can pop on or near the boundary, and root to it, not behind this cold pool the elevated stuff is putting down, I think you've got a decent shot at seeing a tornado. Otherwise it might be grungy ground scraping scud, spinups, circulations in rainy messes, and elevated supercell structure.

 

[Mike Marz]

Now it's beginning to look like convection may just continue to fire all early morning and into the afternoon north of the boundary. Seems like our best chance will be for something to become dominant later this afternoon and do its best to grab the boundary, like Skip said... Not quite as optimistic as I was yesterday, o well, can't not chase it. Yuck yuck yuck