A major storm slated to form over Montana beginning Wednesday will spark severethunderstorms over a swath of the nation from the northern Rockies to thenorthern Plains.Large hail and damaging winds will issue from stronger storms eruptingWednesday into Wednesday night over eastern Montana and northern Wyoming to thewestern Dakotas and northern Nebraska. Northern Utah and southwestern Idahowill share in this risk.

Locally, this storm will also drop heavy rain, heavy enough even for localflooding. The heavy rain threat will be highest in Montana, although it willextend to North Dakota on Thursday.

The parent storm will spin northeastward to the southern Prairie region ofCanada on Thursday into Friday, triggering strong winds as well as more heavyrain and thunderstorms.

Story by AccuWeather.com Senior Meteorologist Jim Andrews.