Weather across America

(NATIONAL) A deep low-pressure system will continue to spread heavy snow northward across the upper Ohio Valley through the lower Great Lakes and New England, snow will change over to a period of sleet and freezing rain before changing over to rain across interior Mid-Atlantic, and some heavy downpours, thunderstorms, and high winds can be expected to impact the coastal sections of the Mid-Atlantic up through New England into Monday.

A low-pressure system continues to expand and intensify as it moves across the southeastern U.S. and begins to turn toward the northeast up the Eastern Seaboard. Arctic air already in place across the central and eastern U.S. will work in concert with this dynamic system to deliver a wide swath of more than a foot of heavy snow northward across the upper Ohio Valley through the lower Great Lakes, as the storm center is forecast to track up the interior section of the East Coast through Monday. 

Closer to the track of the storm center, snow that initially falls is expected to change over to a period of sleet and/or freezing rain before changing over to plain rain across interior Mid-Atlantic and up through the lower elevations of New England. 

Along the spine of the Appalachians, snow is forecast to change over to a period of sleet and/or freezing rain as the storm center approaches. The mixed precipitation should then change back to snow following the passage of the storm center. Heavy wet snow is expected across the higher elevations of New England through much of Monday. Near the immediate coast, some heavy downpours, possibly thunderstorms, together with high winds can be expected to precede the storm center as it tracks up the Mid-Atlantic through New England into Monday.

The center of the deep low-pressure system is forecast to move into southeastern Canada Monday night. This will change the precipitation to all snow followed by gradual tapering off of the snow Monday night. Much improved weather is expected to arrive on Tuesday for the Northeast but the size of the departing system will keep winds blustery.

Meanwhile, a cold front across southern Canada will dip toward the northern Plains. An Alberta clipper is forecast to form on the front on Monday and then move toward the Great Lakes on Tuesday. Lingering snow across the Great Lakes will pick up in intensity on Tuesday as the clipper approaches. Farther west, accumulating snow is also forecast across northern Minnesota and northeastern North Dakota. Arctic air behind the cold front will then surge into the northern Plains on Tuesday. Upslope snow is forecast to develop and intensify over the northern High Plains into the northern Rockies on Tuesday as an arctic high-pressure system slides down from western Canada.

Weak onshore flow combined with upper-level energy will develop light rain and higher elevation snow over parts of the Pacific Northwest Monday evening into Tuesday. Moreover, lingering upper-level energy slowly approaching California from the Pacific is forecast to produce scattered areas of rain Monday evening into Tuesday for southern California. 

Meanwhile, a new low-pressure system is forecast to form over the southern Plains on Tuesday. No rainfall is expected with this system. In fact, dry conditions with a warming trend is forecast for southern Plains.