Weather across America

(NATIONAL) A deep upper low will bring windy and much colder weather across a large portion of the western U.S., a high threat of heavy rain and severe thunderstorms quickly emerging over the north-central Plains, a rapidly intensifying cyclone will bring wind-swept rain across the northern High Plains, and critical fire danger is forecast for the southern Rockies. 

A rather vigorous and deep upper-level low continues to push farther into the western U.S., bringing windy and much colder weather across a large portion of the region. Heavy wet snow across the higher elevations of the Great Basin and a good portion of the Pacific Northwest into the northern Rockies will expand eastward into the central Rockies by Sunday night.  This system will also bring quite a bit of wind, especially as a potent cold front passes through the Four Corners region to Wyoming Sunday evening, before spreading into the Rockies and much of the High Plains on Monday as a cyclone is forecast to intensify rapidly over the northern High Plains. An additional foot or more of heavy wet snow is expected to accumulate along the Cascades in Oregon, as well as much of the northern and central Rockies through Tuesday.  

In addition, severe thunderstorms are expected to develop over the central Plains later on Monday ahead of a potent cold front. These thunderstorms will tend to intensify and track toward the north-northeast into the northern Plains and the upper Midwest Monday night where the potent cold front and a warm front collide. The center of the deep cyclone will then track across the northern Plains with wind-swept rain impacting the northern High Plains on Monday.  

The cyclone center is forecast to meander over the northern Plains on Tuesday with the threat of heavy rain and high winds continuing across northern/eastern Montana while cold air wrapping around the deep cyclone will support heavy wet snow over the northern Rockies. Across the eastern two-thirds of the country, the strong to severe thunderstorms found over southern Texas into the mid-Mississippi Valley are expected to gradually taper off into scattered showers and thunderstorms later Sunday night as the associated upper-level disturbance weakens. Farther east along the East Coast, some showers and embedded thunderstorms over the Mid-Atlantic as well as a large swath of moderate rainfall over New England are expected to slide off the coast by Monday morning.

The scattered showers and some embedded thunderstorms associated with the weakened upper-level disturbance will slide eastward and bring unsettled weather across the Tennessee Valley into the Southeast and up into the Mid-Atlantic states through Tuesday. Also on Tuesday, the Ohio Valley, Midwest, into the Great Lakes will see more widespread showers and possibly severe thunderstorms moving in as the lead frontal systems from the northern Plains cyclone quickly arrive. The cool and dreary weather from the Mid-Atlantic to New England will gradually give way to warmer temperatures.  

In contrast, much cooler weather will continue to penetrate the western U.S. with the passage of the deep and vigorous upper trough/low along with windy and inclement weather closer to the elongated cyclone.  Finally, windy and dry conditions are forecast to raise the danger of wild fires across the southern Rockies through the beginning of the week.