Weather across America

(NATIONAL) A robust low pressure system is bringing the first widespread wintry weather event of the season across the Rockies into the High Plains, severe weather is possible Sunday night over the northern to central Plains, and another low pressure system will bring a quick round of heavy rain, strong to severe thunderstorms across the central U.S.

A low pressure system exiting the northern and central Rockies is forecast to intensify further and continue to bring the first wintry weather event of the season into the northern High Plains through Sunday night. A cold air mass from western Canada will be ushered into the region behind the intense  low pressure system, resulting in rain changing to a period of accumulating snow across the northern High Plains. 

Northwesterly winds behind the storm center are expected to strengthen to gale force with stronger gusts along with falling temperatures. The storm is forecast to be near peak intensity Monday morning as it tracks northeastward into southern Canada. 

Improving conditions are expected to set in as the storm moves farther away, with the snow and winds gradually taper off later on Monday. Behind the storm, much below normal temperatures will surge all the way through the western U.S. and into much of the northern and central Plains, replacing near record high temperatures upward to 90 degrees Sunday afternoon to below freezing by Tuesday morning.

A Wind Advisory remains in effect through much of the central US, including the northern half of Oklahoma which remains in effect until 1 a.m. Monday. South winds 15 to 25 mph with gusts up to 45 mph are expected in portions of northwest Arkansas and east central, northeast and southeast Oklahoma.

Meanwhile, Hurricane Roslyn has made landfall and is weakening rapidly over the mountainous terrain of central Mexico. Higher level moisture associated with the remnants of Roslyn is forecast to interact with the trailing cold front associated with the deep cyclone over the northern Plains. This interaction is forecast to spawn a new low pressure system over the southern Plains on Monday. Rain and thunderstorms are expected to quickly develop and expand across the southern Plains toward the Mississippi Valley on Monday as this low pressure system deepens along the front. 

Excessive rainfall and severe thunderstorms are possible on Monday into early on Tuesday ahead of this system. During the day on Tuesday, areas of locally heavy rain together with strong to severe thunderstorms are forecast to move farther northeast across the Mississippi Valley into the Midwest.

Near the East Coast, a slow-moving front will keep damp and rainy conditions through much of Monday mainly from the Mid-Atlantic coast northeastward into coastal New England. Southern New England could see a round of heavier rain during the day on Monday from this system. By Tuesday, the rain should be slowly tapering off as the front is forecast to gradually dissipate but the clouds will likely linger.

Moisture associated with the next Pacific system will rapidly reach the Pacific Northwest late Sunday night, bringing with it the next round of rain to the lower elevation of the Pacific Northwest and high-elevation snow from the Cascades on Monday, reaching into the northern Rockies by Tuesday.  

Another plume of moisture from the Pacific is forecast to reach the Pacific Northwest coast later on Tuesday.