A low pressure system is forecast to deepen as it inches over the southern Plains. As warm, humid air interacts with this system, strong to severe thunderstorms will develop across the nation's midsection. Severe thunderstorms will be possible over Wyoming, Colorado, New Mexico, northern Texas, Kansas, Oklahoma and western Nebraska. These thunderstorms will be capable of producing large hail, dangerous straight line winds and isolated tornadoes. Monsoonal moisture will also bring scattered showers and thunderstorms to parts of the Great Basin and the Desert Southwest. The West Coast will stay mostly clear of precipitation due to a ridge of high pressure over the eastern Pacific.
Meanwhile, an area of low pressure will push east northeastward over southeast Canada. A cold frontal boundary associated with this system will extend across the Northeast, the Mid-Atlantic and the Gulf Coast on Wednesday. As this front overruns a warm, muggy air mass, widespread rain and thunderstorms will develop across the Gulf Coast, the Southeast and the Eastern Seaboard. The strongest storms will focus over the northern Mid-Atlantic and New England. Light, scattered showers will also be possible across the upper Midwest and the Ohio Valley.