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Northwest Lowland Snowstorm Could Be Huge

Jan 16, 2012; 1:37 PM ET

It's going to be a rough week trying to go through the Cascade passes this week, but it could be quite hazardous in the lowlands of western Washington and northwestern Oregon as well.

One cold air mass moved into the Northwest over the weekend, and with that has been snow showers that has brought accumulating snow already. But this is just the start. A second push of arctic air is coming south through southern British Columbia and will spread south across Washington and northwestern Oregon tonight into tomorrow. Accompanying this boundary will also be a fairly decent 500 mb short wave coming in from the Pacific.

Snow showers will increase tonight across the area and continue into tomorrow. Most of the lower elevations of western Washington will get 2-4 inches of snow with perhaps 1-3 inches in northwestern Oregon by later tomorrow. Meanwhile, a cold, moist, west flow will cause more substantial snow in the Cascades where 1-2 feet of new snow will fall in the next 24 hours.

A much more substantial storm will move east across the Pacific and inland into the Northwest later Tuesday night and Wednesday. There is no doubt that many places in western Washington along the very populated I-5 corridor will get a blast of heavy snow. Eventually, in at least parts of the area, warmer Pacific air eventually turns the snow to rain. However, that will only occur so far north and beyond that snow falls the entire time, and thus this is the crux of the problem today.

Some places just north of the boundary that stay all snow will probably get more than a foot of fresh snow late Tuesday night and Wednesday. But is that Seattle and just north, north of Seattle toward Everett and Mount Vernon up to near Bellingham, or does it occur from just the Tacoma area to Everett? This all depends on exactly where the low pressure moves. The models are not in great agreement, but most of the models are trending to all snow more often than not in and around the Seattle area. Also, north of where the low comes ashore, there could be local blizzard conditions with funneled east winds blowing and drifting the snow.

Farther south from just south of Portland to Vancouver, there is the likelihood the snow will change to snow. Most likely, accumulation is 2-4 inches in Portland. However, up the Columbia Gorge, the cold air will be very reluctant to leave, so snow accumulations will be higher, and there is also the possibility of ice developing and building up.

One thing that is certain, the central and northern Cascades are going to get a dumping. Expect 2-4 feet of new snow late Tuesday night and Wednesday, that's on top of the 1-2 feet expected in the next 24 hours. Travel through the Sierra is not just going to be rough; it may just be impossible.

Back to the lowlands... no matter how you slice it, travel through at least Wednesday morning along the busy corridor is going to be slick, and by Wednesday morning rush, it could be quite dangerous. Total snow accumulations this week in at SEATAC will probably exceed normal for a whole winter. As we get closer to the big event, we may be able to pin things down more. But up until Tuesday night, I have a feeling there are going to be differing opinions of the models and differing opinion among meteorologists. These differences are to be expected and to tell you the truth I probably could see reasons for any opinion possibly being right. In the end it will be up to Mother Nature to decide. Personally, I would expect the worst, and if it turns to be better, fine.

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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