Winter weather parked over a stretch of the United States from Montana to Illinois was expected to bring snow Thursday and potentially disrupt travel later this week.

Most areas were expecting under 6 inches of snow on Thursday, though parts of Wisconsin, Minnesota, and Iowa could see up to 9 inches of snowfall and gusty winds.

But a winter storm warning was also in effect in Oregon and Northern California, where some areas were expecting up to 6 feet of snow and winds to gust as high as 80 mph.

In addition, a flood watch is set for California on Thursday as a storm associated with an atmospheric river stretched over the state.

Here’s what you need to know:

What is an 'atmospheric river'? These rivers of water vapor can extend thousands of miles.

What is a flash flood watch or warning? Here's what to know about this deadly weather hazard

Winter weather extends from Montana to Illinois

Winter weather advisories and winter storm warnings impacted a stretch of states from Montana to Illinois on Thursday, with up to 9 inches of snow expected over a patch of Wisconsin, Minnesota, and Iowa.

A winter storm warning was in effect in the Midwest states from noon Thursday to 6 a.m. on Friday, with snow accumulations of one inch per hour possible in the afternoon and evening, according to the National Weather Service in La Crosse, Wisconsin.

In parts of South Dakota and Wyoming, a winter weather advisory was in effect until Thursday evening, with snow accumulations of up to 5 inches possible and wind gusts of up to 35 mph in the forecast.

AccuWeather meteorologists said upcoming wintry weather in the area isn’t expected to turn into a major storm, but it could bring flight delays to Chicago, Detroit, and other area airports.

Heavy snow slams down on California, Oregon

A winter storm warning was in effect on Thursday in parts of northern and central California. Western Plumas County and nearby areas were expecting up to 6 feet of snow accumulation, with winds of up to 80 mph.

Other parts of the state aren’t expecting as much snow, though some mountainous areas in Shasta County, California, could see snow accumulations of up to 2 feet and winds as high as 45 mph.

In southern Oregon, heavy snow was also expected at higher elevations. Some areas over 3,000 feet could see up to 2 feet of snowflakes, with winds reaching up to 65 mph.

Winter storm tracker

Flood watch reaches into Southern California

A flood watch is in effect beginning Thursday and extending into the weekend across a swath of the Golden State, from parts of Northern California to the San Francisco Bay Area to Santa Barbara and San Luis Obispo counties.

Runoff could lead to flooding of rivers and streams, as “a slow-moving atmospheric river storm system will result in many hours of steady moderate to heavy rain,” the National Weather Service in Los Angeles warned.

• What is an atmospheric river? They're streams of water vapor that can extend thousands of miles from the tropics to the West Coast, fueling rain and snowstorms that may cause flooding.

The weather service warned that people “in areas prone to flooding should be prepared to take action" and warned to not cross flooded roadways.

US weather watches and warnings

National weather radar

This article originally appeared on USA TODAY: Thursday weather forecast: California could see feet of snow, flooding