The nation’s weather


Weather Underground Forecast for Monday, September 12, 2016

A cold frontal boundary will dig into the northern tier of the country on Monday, while a ridge of high pressure builds across the East Coast.

A low pressure area will transition quickly eastward across central and eastern Canada. A cold frontal boundary associated with this system will extend southwestward from the upper Mississippi Valley to the Great Basin. As cold air collides with warmer air east of the frontal boundary, showers and thunderstorms will break out across the upper Midwest, the central Plains, the Intermountain West and parts of the Great Basin. As mentioned, a cool air mass will trail the frontal boundary. This cool air will support high elevation snow showers across the northern Rockies. Snow levels are forecast to drop to 5,000 feet in parts of Idaho, Montana and Wyoming. Winter weather advisories are in effect for western Montana. Additionally, scattered monsoonal thunderstorms will be possible in eastern Arizona and New Mexico.

Meanwhile, the tail end of a cold frontal boundary will sweep across the Deep South and the Southeast. This frontal boundary will be the focal point for showers and thunderstorms, affecting areas from the western Gulf Coast to the Carolinas. High pressure will build across the Mid-Atlantic, keeping most of the Midwest and the Northeast dry on Monday.

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Temperatures in the Lower 48 states Sunday have ranged from a morning low of 26 degrees at Afton Municipal Airport, Wyo. to a high of 102 degrees at Needles, Calif.