7/13/09 FCST: MT/ND/SD/WY

[Scott Weberpal]

Looks like another chase prospect along the SD/ND/MT border this coming Monday. Again, it appears initially high Tdd will be a mitigating factor for tornadoes early, but should increase toward evening/night as moisture advection increses on a strong LLJ throughout the day.

H7 temps look quite warm south of the SD/ND border but rapidly cool north of there. Regardless, it looks like another supercell/potential tornado event this coming Monday.

 

[Mike Hollingshead]

Sucks the system has slowed on tonight's run. I gotta wonder though if one can get something in a more nw flow further east on the warm front. Scary shear there. NAM lights it up(or just moves a MCS south from ND I guess).

Mitchel SD 0z

Chamberlain SD 21z

Gotta wonder what it will spit out tomorrow morning for Tuesday now that it's slower. But still, Monday looks a bit interesting regardless. One of these days the high cap bust potential has to pan out.

GFS still saying go to western Dakotas. Seems as though this time one would have a little better pooled moisture in place to go west.

 

[Bill Schintler]

Storm Chasing Target for Monday, July 13:

Fruitdale, SD (38 miles northwest of Rapid City).

Timing and storm mode:
Storms will likely initiate over the higher terrain of the Black Hills by mid-afternoon, and then spread east and northeast towards the target area through 5 PM CDT. Evolution into a large storm complex with embedded supercells appears likely, with a minor tornado threat.

Discussion:
Low pressure will organize over northeastern WY in response to strong lift provided by a coupled H3 jet structure and strong divergence aloft. A trough will sharpen and extend SE and then E of this feature along the NEB/SD line, with increasingly backed flow over western SD after 18Z. This will aid in continued moisture transport with SFC dewpoints climbing into the mid-60’s, which is sufficient given the elevation of the area between 3000 and 3500 ft. MLCAPEs AOA 3000J/kg will develop as steep mid-level lapse rates in excess of 8.5C/km overspread the area courtesy of the EML. LLVL shear will increase after 00Z as a SLY LLJ strengthens to 45-50kts, with SFC-3km SRH’s approaching 500m2/s2. The SPC SREF ensemble indicates a Significant Tornado Parameter of 3-4 after 03Z. The aforementioned LLJ will also aid in the maintenance of a large convective complex that will track E through SD during the overnight hours.

- bill
10:07 PM CDT, 07/12/09