06/16/10 FCST: MT/WY/ND/SD/NE/CO/KS

[Mark Blue]

I decided to start a thread for tomorrow in the northern, central, and high plains with the next upper level trough that is forecast to arrive and usher in SW flow aloft, which will create quite a stir over the next few days. Tomorrow is the day before the big day, but definitely worth watching. Strong surface cyclogenesis will take place in Montana and deepen in response to the height falls with the approach of the trough. Modest moisture will advect northwards with low to mid 60 dewpoints arriving by late afternoon. I like the warm front play right along the South Dakota and North Dakota border tomorrow with a position of something like Hettinger or Bowman ND where the winds will be backed in response to the surface low west of there. Here's a couple of links to the forecast Skew-T and hodographs for that location tomorrow at 0Z (click 36 hours or less to equal 0Z).

http://tinyurl.com/2ap9dfa

http://tinyurl.com/2ea77a2

Some of the parameters are downright insane and hard to believe in the Skew-T details (take a look for yourself). With the upper air divergence spreading across the region and a low level jet kicking in during the early evening hours, a window of opportunity exists for tornadoes as low level shear will be enhanced right after dinner time. This may end up being a 3Z type of event, but either way it should be before dark. LCLs are manageable, but could be lower. Dr. Forbes has a few moderate Tor:Con indexes in the 5 range for tomorrow in that general area and further south into western Nebraska, and I feel he will probably go higher if things come together the way they hopefully will with a little luck.

I'd be interested in hearing from the chasers who live up north as it's been kind of quiet for you guys lately. Please chime in!!!

 

[Andy Jackson]

It's hard to tell, it seems like that area is the best for tornadoes in ND. If capping is not an issue it will definitely happen.

 

[Greg Blumberg]

I'm trying to stay away from forecasting by the models this summer in order to test my skills projecting the atmosphere forward in 24 hours or so, so I won't be mentioning them much in my discussion.

This is a rather interesting event coming together. Per recent GOES West WV imagery, it seems the jet is strengthening on the west side of the approaching trough. Watching the jet and trough approach the area for tomorrow has me thinking that the forecast from the models about the intense cyclogenesis should verify.

I can see the capping as potentially being an issue, but depending on how the trough shapes up at 12z we'll see how dynamic the system is and get a good idea of what kind of lift we could be dealing with. With the jet still out of the sounding data network and the lack of upper level derived winds being pulled out of the satellite data, I doubt the models are preforming very well when it comes to tomorrow's setup.

If I were chasing, I'd think warm front...mainly due to the potential capping issues. The lift around that area may not be excellent because of the typical nature of the warm front, but every little bit helps.

 

[Bill Schintler]

Chase Target for Wednesday, June 16

Chase target:
Alliance, Nebraska

Timing and storm mode:
Isolated supercell storms may develop after 6 PM CDT. A bust is possible. Given initiation, storm motion will be towards the north-northeast at 20 mph

Discussion:
A shortwave trough over the northwest CONUS will shift slowly eastward while becoming negatively tilted by 00Zm 06/17/10. At the surface, low pressure will strengthen over WY and western CO. Surface dewpoints will slowly increase to near 70F with southeasterly upslope flow. Upstream 00Z soundings (RIW, DNR, GJT, and SLC) indicate steep mid-level lapse rates. Differential advection of moisture and an EML will result in MLCAPE's in excess of 2000J/kg. Capping is a concern, with H7 temperatures in excess of 12C over western NE. Model soundings within western NE indicate a convective temperature of nearly 90F. Moderate assent arrives after 21Z, with omegas of approximately -5 ub/s spreading into western NE. An area of CI will spread from eastern WY into the NE panhandle by 00Z, visually signaling the arrival of stronger assent. Tornado potential should increase during the early evening hours as the LLJ increases to 40 kts while LCL heights decrease.

11:21 PM CDT, 06/15/10
Bill Schintler
www.twistertoursusa.com