A bomb cyclone that slammed into the Pacific Northwest with hurricane-force winds, knocking out power and leaving at least two people dead converged with “an atmospheric river” of moisture expected to bring heavy rain and snow to much of the same region.

The National Weather Service said an additional six to 12 inches of rainfall was forecast for parts of northern California through Friday while heavy snow was possible from the Washington Cascades to western Montana, Idaho and northwestern Wyoming through early Sunday.

The excessive rain and snow comes on the heels of a bomb cyclone that pummeled Washington state, where inland gusts of up to 77 mph were recorded.

According to PowerOutage.us, more than 300,000 customers were without power in Washington state early Thursday.

ABC News reported that a woman was killed when a tree fell into a home in Bellevue, Wash., while she was in the shower. Another woman was killed in Lynnwood, Wash., when a tree fell on a homeless encampment, officials there say.

The “atmospheric river” event was one of two major storm systems affecting a large swath of the United States as millions of Americans are preparing to travel next week for the Thanksgiving holiday.

• Read more from Yahoo Life: How to stay safe and warm in winter weather: Experts’ tips for your home, your car and your family

Near-blizzard conditions in the Plains

According to the National Weather Service, a second system — which brought severe thunderstorms to the central and southern Plains and triggered a tornado in Oklahoma early this week — collided with arctic air, causing widespread snow to develop across the Dakotas, Minnesota and Wisconsin.

Heavy snow and gusty winds that created near-blizzard conditions across the northern Plains Wednesday could do so again in the upper Midwest Thursday.

Snow from the mid-Atlantic to Northeast

Separately, an upper-level low-pressure system was forecast to develop above the Great Lakes Thursday, resulting in cooler temperatures, cold rain from the Ohio Valley to the East Coast and accumulating snow for the central Appalachians, the weather service said.

Winter weather alerts have been issued from the mid-Atlantic to the Northeast, where up to a foot of snow is possible on Thursday and Friday, especially in the higher elevations of West Virginia and Maryland, the weather service said.

While most people in the northeast and New England will see rain, at least six inches of snow is expected to fall across portions of northeast Pennsylvania and New York’s Catskill mountains through the end of the week.

What about Thanksgiving?

Weather service forecasters have yet to issue forecasts beyond seven days, but if any of the impacts linger, the severe weather outbreak has a chance to snarl holiday travel.

Nearly 80 million people are expected to travel more than 50 miles for Thanksgiving next week, according to AAA, with Tuesday and Wednesday expected to be the busiest times on the roads.

• Read more from Fox Weather: Thanksgiving travel could break records this year but extreme weather could snarl pre-holiday traffic