Western Storm to Unleash Additional Round of Rain, Mountain Snow

The final storm of the persistent storm train since the beginning of December will spread across the northwestern United States through the weekend.

"The heaviest snow and rain with the weekend storm will focus over Oregon and part of northern California," AccuWeather Senior Meteorologist Alex Sosnowski said.

Rainfall amounts between 0.50 of an inch and 1 inch could fall in Seattle through Sunday night. Another 1 to 2 inches of rain may fall across Portland, Oregon. Up to 4 inches of rain can fall across southwestern Oregon and northern California.

Snow levels will drop through the weekend with feet of snow expected to fall across the Cascades, Sierra Nevada and the Bitterroot Mountains of central Idaho.

Flooding and the potential for mudslides and debris flows will continue through the weekend.

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Motorists driving through mountain passes will need to be prepared for slippery travel. Chain laws may go into effect for some of the passes.

Those driving along Interstate 5 should slow down in areas of heavy rain to reduce the risk of hydroplaning.

"Enough rain can fall at lower elevations west of the Cascades to be of concern for people living along or taking secondary roads across the smaller rivers, Sosnowski said. "The short-run rivers to the west of the peaks of the Cascades will be very susceptible to flooding through the weekend."

Many locations have received more than their normal December precipitation amount in just the first 10 days of the month. While this has helped the significant drought across the region, flooding and structural damage has resulted from these storms.

Track the rain and snow this weekend by using ​AccuWeather Minutecast®.

Enough moisture will be present for showers to make an appearance across Southern California during Sunday night.

By early next week, a break in the storms will occur across the northwestern U.S., as snow will then focus on the Intermountain West.

"Storms will continue to move in from the Pacific Ocean next week," AccuWeather Senior Meteorologist Brett Anderson said. "However, the storms will not bring as much precipitation and should have greater separation from one another, when compared to the past couple of weeks."

"While there will still be the potential for incidents of flooding and mudslides, the number of incidents should decrease in the Northwest during the third week of December," Sosnowski said.

Cold air will dive into the Western states early next week. Much of the West Coast will miss out on the worst of the cold.

The weather will be favorable early next week for any clean-up efforts and to restore power.