From Portland National Weather Service
A cold front will bring low snow levels Saturday night through Monday, followed by a very active weather pattern bringing a series of storms mid week.
A cold front drops south from Alaska ushering a cold air mass into SW Washington and NW Oregon beginning late Saturday, then settles in place by Sunday. Showers will spread across the area with lowering snow levels Saturday night. Snow accumulation of a few inches are possible through Monday from elevations of 500 to 1000 feet and above, though in a showery air mass accumulation of snow can vary significantly. Snow showers will likely reach the valley floor at times and in heavier showers snow may accumulate briefly.
A change to a more mild, but wet and windy pattern sets up as a series of storm systems will affect the area beginning Tuesday and likely to continue through late next week.
The transition out of the cold air mass may bring a mix of wintry weather with more low elevation snow or freezing rain in and near the Columbia River Gorge sometime on Tuesday. In the Cascades, significant snow accumulations will likely make travel across the Cascades difficult.
Strong winds are also possible at times, especially on the coast and in the mountains, while a moist air mass may bring heavy rain as the storms make landfall. Interior lowlands may also
see some windy conditions and heavy rain as well. Rivers and streams are likely to respond with sharp rises.
At this time, details on the timing, strength and track of the storms are somewhat uncertain. Stay tuned for future statements and forecasts for the latest information.