USA National Weather Service update

...Excessive rainfall and flooding potential continues across the Pacific Northwest over the next few days...

...Moderate upslope snow forecast across the central Appalachians into Wednesday...

...Warming trend increases across the Great Plains through midweek...

A strong atmospheric river impacting the Pacific Northwest is expected to continue soaking the region with heavy rain through Wednesday until precipitation becomes scattered. Warm air associated with the stream of moisture extending from the subtropical Pacific will continue to allow for very high snow levels through early Wednesday, which will exacerbate the flooding potential due to snowmelt and increased runoff. Several additional inches of rain are forecast across western Oregon and Washington, as well as northern Idaho by midweek. Flood Watches, Warnings, and Advisories have been issued for this part of the country. Residents are advised to never drive through flooded roadways and have a plan if within an area that typically floods. By Wednesday night into Thursday, much of the precipitation should finally begin to weaken and shift eastward throughout the northern Great Basin and northern Rockies, which will allow for heavy mountain snow for many of the elevated ranges.

An Alberta Clipper system continuing its trek across the Nation will also produce areas of snow from the Ohio Valley and Lower Great Lakes to the central Appalachians into Wednesday. Snow will be mostly scattered and light, except for the Allegheny Front of West Virginia and western Maryland. Here, subfreezing temperatures and upslope flow from the northwest will allow for moderate to locally heavy snow across the high terrain. Winter Weather Advisories have been issued for the region forecast to receive at least 3 inches of snowfall. Elsewhere, light snow showers are possible across New England and light lake effect snow is possible downwind of the Great Lakes through midweek.

The rest of the CONUS can anticipate dry conditions as high pressure anchors overhead. Temperatures are forecast to remain slightly below average along the East Coast and Southeast, while a warming trend kicks off across the central United States. Highs on Wednesday and Thursday should reach the 60s in the central Plains and 70s in the southern Plains, with temperatures anomalies of 20 to 30 degrees above average extending into the Middle Missouri Valley. Daily high temperature records will be at risk of being tied/broken from Nebraska to Wisconsin on Thursday.