My target: Luverne, MN...
Both the RUC and ETA develop signficant instability (4500-5000 SBCAPE off the ETA and ~3000 SBCAPE if you believe the RUC) in a corridor generally from Pipestone, MN, south-southeastward into western IA. The RUC drops sfc Tds into the mid-upper 60s for the most part, while the ETA increases sfc Tds into the mid-upper 70s -- thus the CAPE forecast discrepancy. Whatever the case, current showers and clouds in the sw MN, se SD, and nw IA area will likely inhibit the development of strong surface-based instability for several hours. While mid-levels remain relatively weak, strong directional shear yields ETA-forecast 0-6km deep layer shear of ~35kts by afternoon from southwestern MN into western IA. Additionally, s-se SFC winds beneath s-sw 850mb winds yields respectable 0-3km helicity in the 200-300 range. Both the RUC and the ETA show a weakness in the cap over sw MN and adjacent portions of far se SD and nw IA by afternoon. While the ETA QPF output seems to develop an MCS west of Pipestone (moving east-southeast) while keeping the 'warm sector' capped, the RUC does develop precip from near Watertown, SD, to FSD to south of Denver, along the front trailing from the low in se SD.
With decent low-level shear and potentially-strong instability, I think, assuming initiation, we could end up with a couple of tornadic supercells from southwestern MN into far northwestern IA (the cap increases to the south, so....). Weak midlevel SR flow will likely tend to put any supercells in the HP range, but, as we've seen many times this year with relatively-weak mid-level flow, we can still end up with photogenic tornado-producers.
I haven't looked much as the southern SD or NE forecast, since I'm partly doing this to aid a friend (Gabe Garfield) who's up there chasing today...
