The eastern United States is bracing itself for the first heavy storm of the season, with torrential downpour and snow expected from Tennessee to Michigan on Monday, and rain then drenching neighbouring regions.
The storm is expected to form over the deep south on Sunday, with heavy rain.
Strong to severe thunderstorms could also develop in the warm, humid air ahead of the storm from the southeast on Sunday to the eastern Mid-Atlantic on Monday.
The storm will be accompanied by high winds, causing drifting snow.
Gusts could top 40 mph on Monday in the eastern Great Lakes, possibly causing blowing and drifting snow around Cleveland and Detroit. Powerlines could be knocked down, experts warn.
Into Tuesday morning, snow is expected to arrive in western New York and western Pennsylvania, as the storm dissipates.
Scientists are still calculating the impact, but it is expected that the heaviest snowfall - at least several inches - will be over the areas around Indianapolis, Detroit and Cleveland.
Travel could be difficult in those regions.
A huge swathe of the country is being told to expect heavy rain.
Locally heavy precipitation will impact the Gulf Coast and Southeast this weekend before advancing into the Mid Atlantic and Northeast by Monday. pic.twitter.com/t035ZXgupH
— National Weather Service (@NWS) November 28, 2020
From Louisiana to Maine, at least an inch of rain is possible, with two to three inches or more along the Gulf Coast and in eastern Maine.
The storm will help to draw very chilly air into the Southeast and Mid-Atlantic on Tuesday, where temperatures will be 5 to 15 degrees colder than normal.
And, looking ahead to December, the mild weather of November will not last.
Experts say that, while an influx of freezing Arctic air is not expected, temperatures will generally hover slightly below normal for the month’s first week.
A second storm is expected at the end of the first week of December, although its precise track is not yet known.