7/23/05: FCST: WI/MN/IA

[nickgrillo]

Just wanted to start a thread for the upper midwest on Saturday. The latest 12Z NAM paints a pretty good supercell picture across MN/WI. A strong shortwave pushing east, with good moisture pooling at the SFC (and CAPES AOA 4500J/KG), in addition to helicity values in excess of 450 m2/s2 would lead me to believe that there is a supercell, and associated tornado threat across WI/MN -- with any activity that becomes SFC-based.

I would really love to chase on SAT, but I think it is a bit too far of a drive... I am also thinking that SUN could have a severe threat closer to home as well.

 

[Justin Turcotte]

I'd like to see another run or two in the models before hitting the details. That said, both GFS and NAM in pretty good agreement with synoptic features. Both models have an MCS riding the building ridge during the early morning hours. This would have a signifiacnt impact on location of convective redevelopment during the afternoon. While shear and instability parameters are robust, the cap looks wicked with H70 temps in the +13 to +17 range in the targeted area. I am somewhat entertained by the trough that will propagate through ND during the afternoon. The cap will be weaker there and CAPE high but shear could be reduced if the MCS redirects the LLJ. No shortage of mid and upper flow however. There would also be the possibitlity of an intersection of the trough and potential retreating OFB.