Skip Talbot
EF5
An interesting and dynamic setup looks like its shaping up over southern MN/northern IA/western WI on Wednesday. A 70 knot midlevel jet is forecast to eject across the northern plains during the evening, along with a strong southwesterly low level jet, and backed surface winds of 10-20 knots. The speed and directional shear look very favorable for supercells, although I'm still worried a bit about storm mode. The NAM has been forecasting ongoing precip throughout the day along the MN/IA border. The instability is actually forecast to hit 3000 J/Kg across portions of northern Iowa by noon and into Minnesota shortly afterwards, and with the strong low level jet the tornado parameters are quite high throughout the day. The problem is there is a super stout cap also forecasted, and it holds its grip until after 21z before finally eroding in northeast Iowa and southeast Minnesota. Given the strong instability early on with the ongoing storms, but with the strong cap, I expect elevated supercells with a severe hail threat most of the day across Iowa and Minnesota. As the cap weakens later in the afternoon/evening, hopefully we can see these storms become surface based and that will give us a better shot at tornadoes. There could be a lot of storms throughout the day including cluseters and embedded supercells, which will put down a myriad of boundaries. We could see new development of surface based supercells east and south of the ongoing storms, and this might be the more chaseable play. Anyway, it looks like a complicated forecast that will hinge on what happens tomorrow further west as well as the ongoing precip in the morning, but the shear and instability are there for supercells and tornadoes.
