Ken Clark

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Heavy Snowstorm East of Cascades as Well

January 17, 2012; 1:30 PM

AccuWeather.com has been playing up since early last weekend a big snow possibility for Seattle and other areas from the Cascades on West. I have also had a couple of postings on this. However, sort of lost in the shuffle are areas east of the Cascades and north-central and northeastern Oregon and that is where I will concentrate on this posting.

In many areas east of the Cascades, it's not all that cold right now. There has even been a few rain showers in parts of south-central Washington, but this map shows much colder air to the north and its pressing south.

Cold air will continue to press south through tonight. Meanwhile, moisture is on the increase from the west as a large overrunning shield of precipitation is spreading east across the eastern Pacific as can be seen by the clouds on satellite picture.

The moisture continues to move in from the west late tonight and tomorrow while the colder air presses south. This is setting up a classic heavy snow scenario on the east slopes of the Cascades and parts of the Columbia River Basin on north and east. How far south the cold boundary get will decide where the heavy snow ends and a transition of ice to rain will take place. It is likely that warmer air will take over Wednesday in places like Bend and Redmond turning snow to rain. But farther north most all snow occurs with probably snow and also perhaps some ice along the Columbia River. A fairly wide swath of 5 to 10 inches of snow is likely in central and eastern Washington and the Blue Mountains while in northern Oregon a period of snow changes to ice, and in places rain with 2 to 6 inches of snow and ice before the changeover.

For western Washington. It looks like cold air is able to hold on through all of Wednesday and even Wednesday night around and north of Seattle so mostly all snow is likely. The heaviest snow outside of the Cascades is probably from near Tacoma on north to Everett with lighter amounts farther north deeper into the cold air. In the band of the heaviest snow as much as a foot of snow can fall with many places getting 7 or 8 inches. Also north of where the low comes ashore strong east and northeast winds are likely making for blowing snow conditions reducing visibility. In Southwest Washington and northwest Oregon snow will likely change to rain with 2 to perhaps 4 inches of snow before a changeover. But around the Gorge it is more likely that snow, some heavy, changes over to ice with 4 to 8 inches of snow before a changeover.

Eventually the cold air will give up, but in some section of northwest Washington it may take until sometime on Thursday for that to happen. East of the Cascades north of the Columbia River Basin some snow and ice can continue to fall all day Thursday.

It is going to be very interesting to see how all this transpires. Small differences in where the Pacific low tracks and how much the arctic truly presses.

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

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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.