9/7/05: FCST: SD

[nickgrillo]

Pretty good setup... Strong directional shear through the troposphere -- With backing winds at the SFC, veering to the W-NW at 90KTS at 200mb! Low-level moisture ain't too bad, considering it's September in the Dakotas... With Td's in the 55-65 range, with temperatures only in the 75F-80F range across the majority of the area. All in turn will lead to rather "doable" LCLs... And considering the 20-30kts and 850mb, low-level shear is pretty impressive with 200-400 SRH. Deep instability should be realized as well, with CAPEs forecasted to be in the 2000-3500J/KG range across most of the area. There should be enough convergance along / north of the front for convective development across southwest/westcentral SD by mid-afternoon as the inhibition will slowly decrease with afternoon insolation. Overall, given the instability/shear combo - supercells / isolated tornadoes should indeed be posssible today.

Virtual chase target: Rapid City, SD area (actual target will be the place I work at here in DTX :lol: :lol

 

[Justin Turcotte]

Definately a good set-up for supercells given excellent turning with height of the winds. Shortwave noted at H70 to be the kicker. Easterly uplsope flow will aid in lift. I suspect temperatures will be a bit warmer, perhaps into the mid 80's. Dews look to be in the mid to upper 50's and possible local low 60's but still a sizeable temp dew spread. CAPE probably overstated unless more juice can get in there but 1500-2000 J/kg is plenty with the shear environment. The 06z NAM shows a weaker wave and not much in the way of convection that the 00z run had. If storms do pop I suspect they will more more of a wind/hail threat.