Winter storm forecast: Most of the U.S. is at risk of extreme weather this week. Here's everything you need to know.

From blizzard conditions in the Pacific Northwest and the Midwest to excessive rainfall and strong winds across the country, forecasters predict how the powerful storms will affect dozens of states.

A snowplow clears winter snow.
A snowplow clears winter snow from Broadway in Methuen, Mass., in January. (Joseph Prezioso/AFP via Getty Images)

The National Weather Service (NWS) is warning of several winter weather systems creating “widespread and potentially significant” flooding across the central Gulf Coast, the East Coast and even Hawaii, as well as “ferocious blizzards” in the Pacific Northwest and the Plains into the Midwest.

Forecasters are pleading with residents in the affected areas to take the “really unusual” weather in some areas seriously as they brace for the “extremely dangerous” conditions.

Pacific Northwest

The NWS predicts that “blizzard conditions are likely” as a major winter storm sweeps through the Pacific Northwest. Residents in Washington state and the Oregon Cascades will see several feet of snow through Tuesday. A wind advisory for parts of Oregon and Washington state has been issued through Tuesday morning as wind gusts kick up to about 55 mph.

In northwest Washington state, the NWS issued a flood watch through Tuesday morning as “excessive rainfall” beats down across the south slopes of the Olympic Mountains. Forecasters are expecting between 2 to 4 inches of rain.

The Washington State Department of Transportation called it “REALLY unusual” for the NWS to issue a blizzard warning in that area.

“PLEASE take this seriously,” the Washington officials said in a tweet. “Our crews will be out, but we lack the ability to stop heavy snow and high winds. It's going to be REALLY challenging in the passes.”

Plains and Midwest

A “deep and dynamic” cyclone will cause “ferocious blizzard conditions with whiteouts” for the central and southern Plains of the U.S. — which include South Dakota, New Mexico, Oklahoma, Texas, Colorado, Nebraska and Kansas — starting on Monday and then heading to the Midwest into Tuesday.

The NWS predicts that the Midwest will get the brunt of the snowfall, where residents could see up to a foot of snow, with wind gusts up to 70 mph. The Weather Service warns that the system will wreak havoc on those who decide to travel.

“Travel will become extremely dangerous to impossible,” the NWS said. “If you must travel, pack a winter survival kit as wind chills will plummet below zero.”

Southeast

Starting Monday night, meteorologists predict “widespread and potentially significant river and flash flooding” for the Southeast as heavy rainfall is expected to pummel the central Gulf Coast and stretch to Georgia and parts of the mid-Atlantic into Tuesday, lasting until early Wednesday.

Nearly 70 million people could be affected by the fast-moving storm system, which is expected to cover almost 2,000 miles of the U.S. in 72 hours, dumping snow on more than half a dozen states.

“Powerful onshore winds will lead to widespread coastal flooding along the eastern Gulf Coast and much of the East Coast,” forecasters said.

Meteorologists also warn of a chance of tornadoes for parts of the south, including Louisiana, Mississippi and Alabama, on Monday night, heading into Tuesday. About 3 to 5 inches of rainfall is also expected, which could be a flood risk.

Northeast

After the Northeast saw its first significant snowfall in two years over the weekend, a “stronger, larger and warmer storm” will bring heavy rain and will also rapidly melt snow beginning Tuesday morning from northern Virginia to western Massachusetts, according to AccuWeather.

The meltdown mixed with excessive rainfall may cause flooding, forecasters warn. The heavy rainfall is also predicted to have a “widespread significant” impact, swelling rivers in the region, which may also cause flooding.

About 62 million people are under flood watches in the mid-Atlantic and Northeast region.

The Weather Service is warning residents across much of the East Coast and New England to brace for wind gusts of about 50 mph and the power outages caused by it. Boston could experience winds similar to a Category 1 hurricane and the NWS is on standby to issue “hurricane-force wind watches.”

Hawaii

The NWS's Honolulu office has also issued a flood watch for all the islands due to heavy rainfall starting Sunday evening and lasting through Tuesday.

“Flood-prone roads and other low-lying areas may be closed due to elevated runoff and overflowing streams,” NWS said in its warning. “Urban areas may receive more significant flooding and property damage due to rapid runoff.”