...Heavy precipitation for the Cascades...
...Heavy snow possible over parts of the Northern/Central Rockies...
...Snow to develop over parts of the Upper Midwest...
Deep upper-level troughing will move southward over the Pacific Northwest into Northern California/Great Basin. The associated cold front will likewise move southward over the Pacific Northwest to Central California/Great/Basin by Tuesday morning.
Onshore flow will accompany the boundary, aiding in light to moderate rain over the Cascades that will change over to snow on Monday. Rain and higher elevation snow will advance southward over the Northwest into Northern California by Tuesday, while the precipitation ends over the Northwest.
A warm front will develop over the Northern High Plains/Northern Plains on Sunday evening and expand eastward into the Middle Mississippi and Ohio Valleys Monday into Tuesday.
The storm will produce snow and lower elevation rain over parts of the
Northern/Central Rockies into the Northern High/Northern Plains Sunday evening into Monday.
Snow will develop over the Upper Midwest on Monday, expanding into parts of the Upper Great Lakes by Tuesday.
Additionally, a few pockets of rain/freezing rain will develop over parts of the Northern Plains on Monday and Tuesday morning. Areas of light rain will develop over parts of Upper Mississippi Valley into the Great Lakes on Tuesday morning.
Meanwhile, a front over the Lower Great Lakes/Lower Mississippi Valley will dissipate as a boundary develops off the East Coast overnight Sunday. Low pressure will develop along the boundary off the North Carolina Coast and move northeastward over the Western Atlantic on Monday into Tuesday. The dissipating system will produce light snow and rain over parts of the Lower Great Lakes through Monday morning. The developing system over the Western Atlantic will aid in producing light snow and coastal rain over parts of Northern New England Sunday evening into Monday morning. Rain
will redevelop over parts of Northern New England by Tuesday morning.
The developing area of low pressure will trigger scattered showers and thunderstorms over parts of the Carolina Coast Sunday evening into Monday, too.
In addition, weak upper-level energy will move over the Lower Mississippi Valley to off the Southeast Coast by Monday night. The energy will produce light rain over parts of the Central Gulf Coast and extending into the Southern Appalachians Monday into Tuesday.