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

The National Weather Service said another 6 to 12 inches of rain is forecast in parts of Northern California through Friday, while heavy snow is possible from the Washington Cascades to western Montana, Idaho and northwestern Wyoming through early Sunday.

The excessive rain and snow follows a bomb cyclone that hit Washington state, where inland winds of up to 75 miles per hour were recorded.

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

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

The “atmospheric river” event was one of two major storm systems to hit much of the United States as millions of Americans prepare to travel for the Thanksgiving holiday next week.

• Read more from Yahoo Life: How to stay safe and warm in winter: expert 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 spawned a tornado in Oklahoma early this week — collided with Arctic air, causing widespread snow in the Dakotas, Minnesota and Wisconsin.

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

Snow from the mid-Atlantic to the northeast

In addition, an upper-level low-pressure system was forecast to develop over the Great Lakes on 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 warnings have been issued from the mid-Atlantic to the Northeast, where up to a foot of snow is possible Thursday and Friday, especially in 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 are expected to fall in parts of northeastern 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 impacts persist, the severe weather outbreak has the potential to disrupt holiday travel.

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

• Read more from Foxweer: Thanksgiving travel could break records this year, but extreme weather could hamper pre-holiday traffic