The same pattern that will bring mild air to much of the nation late this week into next week will trigger a series of drenching storms in the Pacific Northwest.
A fast flow of air will extend across the northern Pacific Ocean right into the Northwest United States starting later this week. While the fast flow will keep arctic air at bay over Canada, it will allow one storm after another to roll onshore over the West coast.
The first storm will move in on Thursday. Drenching rain will spread southward from coastal British Columbia to western Washington and Oregon into the nighttime hours.
Enough rain can fall to cause flash and urban flooding with slow travel along the Interstate-5 corridor in Washington and Oregon with the first storm. Low cloud ceilings can lead to delays at Seattle-Tacoma International Airport.
According to AccuWeather.com Senior Meteorologist Brett Anderson, "South to southwest winds with gusts as high as 50 mph can occur along the Washington and northern Oregon coasts Thursday into Thursday night."
Snow will remain above pass levels in the Cascades Thursday night and Friday, but fog could be a problem for travel in the higher elevations.
A second storm is forecast to move in late Friday and Friday night with a third storm possible on Sunday. Both of these storms will bring locally heavy rain to the coast and west-facing slopes of the Cascades.
The third storm could bring rain to the NFL Postseason game between the Packers and the Seahawks on Sunday in Seattle.
With each successive storm, snow levels will lower a bit, so that there may be an accumulation over some of the passes by late in the weekend.
"Heavy snow will blanket the Cascades of Washington and Oregon and the Coast Ranges of British Columbia," Anderson said.
"There is the potential for up to a couple of feet of snow above 5,000 feet by the end of the weekend."
Locally heavy snow will extend inland over the high country of the Clearwater and Bitterroot mountains this weekend.
Each successive storm will increase the risk of mudslides as the ground become saturated. The risk will be greatest in burn areas from this past summer season.
"The western parts of Oregon and Washington, as well as Vancouver Island, British Columbia, could end up with 2-4 inches of rain by the end of the weekend from the series of storms," Anderson said.
The bulk of the rain with the storms will remain north of San Francisco and Sacramento, California, but some showers can dip as far south as part of the Bay Region to the Sacramento Valley on Friday night and perhaps again by early next week.
No rain or mountain snow of consequence is likely to reach Southern California through early next week.