07/16/05: FCST: Dakotas

[nickgrillo]

Just wanted to start a thread for the dakotas this Saturday. The latest 12Z NAM is painting a pretty good supercell picture across that area. A strong cold front pushing east, with moisture pooling at the SFC (and CAPES AOA 3000J/KG), in addition to helicity values in excess of 350m2/s2 would lead me to believe a pretty decent severe event is probable. The entire column has excellent rotation - winds at the SFC are backing to the SE, veering to the south at 850mb, then veering to the west-northwest at 500mb (in a small area of the dakotas). In addition, given the very high moisture/theta-e, LCL's will be quite low, so it would be easy for a storm to produce a tornado.

Anybody else care to comment?

 

[Justin Turcotte]

I've been watching the model trends on this the last couple days. Sitting at the office putting out the forecast for NDDoT so I gave this a close look...
NAM and GFS are pretty similar with the set-up. I'll go with the GFS for now as it has been the superior model up here this summer. ... Strong sub 1000 mb low for this time of year with attendent warm front located near the ND/Canuck border, possibly setting up further north in Manitoba. Cold front stretching from north to south across central Dakotas. With the magnitude of the low I would expect plenty of backed surface flow enhancing low-lvel shear. The LLJ looks to be thumping along at a good 30 kts from the south with solid 35 kt H70 flow from the southwest. The target region looks to be in the exit region of a sharp jet streak. The area will, however, be under a stout H70 cap with level temps ranging from +13 to +16C, a bit cooler north of the warm front. The GFS advertises a couple of shortwaves in the flow regime which would provide some CAA and lift. I suspect the leading wave riding along the warm front would offer the best hope of tornado action before darkness falls. Possible initiation area along the triple point advertised in the Minot vicinity. Things could get interesting in eastern Dakotas/MN the following day but will leave that for another thread if the threat looks to materialize.

Aside: July is the most climatologically favored month for tornadoes in North Dakota.

 

[Jayson Prentice]

Day 3 outlook doesn't look to impressive... Although still plenty of time for changes. Only slight risk with 15% probabilities, supercells do appear likely along the front given the good shear and instability. Only problem may be the congeling that the SPC talks about as well. With such strong ascent over the area once the storms begin they should have no trouble forming together into squall/MCS.

Overall I think that the hail/damaging wind potential will be greatest, although with such great shear in the area those first storms should have the tornado potential. This system should also continue to affect the rest of the northern plains on Sunday... So far doesn't look like to much interest for this system.

 

[Jared Mysko]

Environment Canada is considering a special weather statement for southern Manitoba for Saturday's severe weather set-up...

http://iwin.nws.noaa.gov/pub/data/text/FOCN45/CWWG.TXT

Looks to me like I will be heading down towards the Estevan area in SE Saskatchewan to see if I can catch some of the action. Hopefully it warms up soon though because it just seems a bit to cool for storms today. Things should come together nicely overnight tonight and since I'm working till 4am , I might see things as they develop in the morning around Saskatoon. Hopefully I can stay close to home but if it looks much better further south, I will make the trip. Think I will take a long nap this afternoon to get ready for little or no sleep tonight!

A team from Winnipeg will be chasing this stuff for sure, i wonder how many other chasers will be on this stuff on Saturday? Here is their blog:

http://wxcentral.blogspot.com/

Jared