The volatile storm system that dumped up to 8 inches of rain along the Minnesota-Iowa border in the past 24 hours is poised to reenergize and deliver another round of strong to severe storms Friday, including the threat for tornadoes.
For later today, the Storm Prediction Center expects late afternoon or early evening development of discrete supercells, which will have the potential to produce tornadoes. The storms are then expected to form a line, at which point the main severe threat would be damaging winds.
As meteorologist Sven Sundgaard notes in his video, where the tornado threat is maximized depends on how far north the warm front gets. As of 1 p.m., the warm front was draped across northern Iowa and moving to the north.
If the HRRR model is remotely accurate, it would mean the warm front could move as far north as the Twin Cities metro by Friday evening. Wherever the warm front is when storms pop is essentially where the tornado threat will be highest – and as you can see in the 1 p.m. update from the HRRR model, storms are projected to pop near, but south and east of the immediate Twin Cities. It might be a close call. We'll see.
"This evening’s activity looks to be mainly just southeast of the metro, though we could benefit from more rain on the northern edge," says Sundgaard. "Tomorrow is steamy: peeks of sun, very humid and leading to a real strong possibility of nasty (straight line winds) storms late in the day and maybe again overnight."
The SPC has already publicized an enhanced risk for severe storms – level 3 of 5 –for a swath of southwestern Minnesota up through the Twin Cities and into western Wisconsin.
Here's what the SPC anticipates taking place by mid-afternoon Saturday: "rapid storm formation across eastern SD, northeast NE and western MN. A linear storm mode appears likely, with damaging wind potential spreading east. The very strong instability may support significant wind gusts."
In other words, there could be damaging winds in excess of 75 mph, in addition to tornadoes during the day.
We'll have more as the situation develops.