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Colder Northwest Weekend with Low-Elevation Snow

Jan 13, 2012; 1:07 PM ET

A cold storm now in the northeast Gulf of Alaska will be dropping south and southeast through the weekend.

As it does, the cold front ahead of it will spread some rain and Cascade snow into northwestern Washington late tonight then south into northwestern Oregon and the northern Oregon Cascades tomorrow. Tomorrow night, the cold front will move through areas east of the Cascades.

Once the front is through, colder air will move in to cause snow levels to drop to very low levels in western Washington and Oregon and east of the Cascades by later tomorrow night and Sunday. Snow levels will drop down to a few hundred feet in western Washington and northwestern Oregon and 500 feet or so in northwestern Oregon to about 1,000 to 1,500 feet in southwestern Oregon. East of the Cascades, precipitation will be more spotty outside of the mountains but still will be near the lowest valley floor at times.

The Cascades above 1,500 feet will likely pick up at least 7 to 14 inches of snow through the weekend. Accumulations in lower elevations west of the Cascades can be highly variable, but there can be an inch or two in spots, especially above a few hundred feet, from northwestern Oregon up the I-5 corridor to northwestern Washington. East of the Cascades, 4 to 7 inches are likely on the east slopes of the Cascades with 2 to 5 inches in the eastern Oregon and Washington mountains. Valley areas could pick up an inch or two in spots. Temperatures will be much colder and by Sunday will be mostly in the 30s west of the Cascades and 20s east.

A moist onshore flow will continue on Monday with more showers likely, especially Cascades on west and around the eastern mountains. Snow levels are likely to stay low as cold air remains in place.

It will get more interesting by Tuesday night and Wednesday. All models have been consistent for the last couple of days about a much wetter storm moving in and that continues to the case today. Rain and snow will be much more substantial during this time and it's likely to become windy as well. Warmer air will try to come in, but with a cold surface high centered to the north, the cold air will offer quite a bit of resistance. This is especially true for the Columbia River Gorge and northwestern Washington. The warmer air will meet with less resistance in central and southern Oregon. Also places east of the Cascades may have a hard time warming up, especially in the low levels, and this could lead to snow and ice problems.

Farther south, a closed low southwest of southern California finally gets booted northeast this weekend. There is somewhat more mid- and high-level moisture ahead of this storm now, and because of that, scattered showers are more likely than a day or two ago. Rain amounts will be light, but Sunday will be a rather cloudy, cooler day which is far different than it was today.

As I said yesterday, the chance of important rain in the Southwest is small through the middle of next week. Meanwhile, storms will continue to move into the Northwest. How far south the precipitation sags in the Tuesday to Thursday time period differs on the models. From the North Bay on north, some rain seems likely. It's more problematic a little farther south. But all models are point to chances of rain moving more south late next week which they have been for a couple of days now.

The views expressed are those of the author and not necessarily those of AccuWeather, Inc. or AccuWeather.com

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About This Blog

Ken Clark
Ken Clark's Western U.S. weather blog tackles daily weather events with commentary from one of the most experienced and trusted Western U.S. weather experts.

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