AccuWeather.com

By Brian Edwards, Meteorologist

Jan 16, 2012; 5:32 PM ET

Share |

Photo courtesy of photos.com.

A return to stormy conditions will prompt concerns for significant snows and flooding rains across much of the Northwest quadrant of the country this week.

A change in the overall pattern across the West will lead to a dip in the jet stream forming over the Pacific Ocean. This dip in the jet will lead to a series of storms making their way onshore in the Northwest over the next week at least.

This pattern will be welcomed by some as much of the West Coast has experienced below-normal precipitation so far this winter.

In fact, places like Crescent City, Calif., and Medford, Ore., have only received 50 percent or less of their normal precipitation since Oct. 1.

The story is even worse in San Francisco and Sacramento, Calif., where they have only received 30 percent of their normal precipitation for the same time frame.

Luckily for residents from northern California to Washington, these precipitation deficits will shrink very quickly over the next week.

As AccuWeather.com Meteorologist Andrew Mussoline pointed out, "A powerhouse storm will slam into the Northwest later Tuesday night into Wednesday, sending a surge of heavy rain and snow into the Pacific Northwest."

Intermittent light rain and light snow will fall over much of the Pacific Northwest through Tuesday. These lighter amounts won't be enough to cause too many issues, though there could be a little snow in the Seattle metro area through tonight. Any snow in Seattle is a big deal as they typically only average 6-7 inches of snow per season at Seattle-Tacoma International Airport.

Beyond Tuesday, things will get very interesting as the aforementioned pattern sets up. As high pressure over the Pacific Ocean sinks southward, a large dip in the jet stream will form over the northern Pacific.

This will send a train of storms aimed right into the Northwestern quadrant of the country.

The first storm will move onshore Tuesday night into the day Wednesday with a secondary front and push of moisture expected Thursday. This storm will bring heavy rains to coastal sections of Washington, Oregon and northern California. Residents from Crescent City to Portland and Quillayute can expect to pick up between 2 and 4 inches of rainfall between Wednesday morning and Friday morning.

Meanwhile, heavy snows in the Cascades will lead to snowfall accumulations on the order of several feet in the highest elevations.

Snow levels themselves will start out very low on Wednesday, especially in the Washington Cascades where the level will be 500 feet or less. As the moisture continues to stream inland Wednesday night and Thursday, snow levels will steadily rise, reaching about pass level or 3,000 feet by Friday morning.

From here, the storm train continues right into next weekend with another storm expected to move onshore on Friday. This one could actually send rain farther south into San Francisco and Sacramento. Not only that, but some snow could make it into the northern Sierra Nevada where they are lacking snow cover for this time of year.

Stay tuned to AccuWeather.com over the coming days as we fine tune the forecast for the West Coast and the potential for disrupting snows in the Seattle area.