A jet stream dip swinging into the Northwest and across the Rockies will help to propel an intensifying frontal system from the Plains to the Great Lakes late Saturday into early Monday of next week. The combination of strong jet stream winds, strengthening low pressure and warm, moist air returning from the Gulf of Mexico will help set the stage for this threat of severe storms, including possible tornadoes.
Initially, a few severe storms may develop as early as Saturday night from southeast Minnesota and southwest Wisconsin to eastern Kansas, northwest Missouri and northeast Oklahoma.
However, it appears the greatest and most widespread threat of severe thunderstorms will be on Sunday.
Source: Weather Channel