It could begin as a wintry mix of rain and freezing rain but transition to snow later in the day on Monday, the weather service said.
Although unseasonably cold air is forecast to linger around into Valentine's Day, it's not known just how cold the air mass will be and if it could be enough to support low elevation snow for Portland and Seattle. The daytime high will be about 31 degrees.
There could be a little snow thrown in there as well, for some.
Areas near the Columbia River Gorge will see east winds gust as high as 30 miles per hour.
Freezing rain is increasing across the area, and will turn steadier this morning into this afternoon. This will lead to a significant ice storm event today, and an ice storm warning is in effect for much of the area through tonight.
Temperatures will hold in the 28-32 range for most areas much of the day.
Maps of predicted areas for snow ice through Saturday. NOAA
Portland and Vancouver, as well as the Cowlitz River Valley, have a greater chance of precipitation falling as mostly snow.
A slight chance of snow and sleet before midnight, then a chance of sleet between midnight and 4 a.m., then a chance of snow and sleet after 4 a.m. The weather service says up 12 inches (30 centimeters) of snow are possible in the White Mountains.
"While a mixture of snow and sleet could add up to an inch or so in spots, expect predominantly freezing rain", says NWS Portland. As much as 2 new inches are possible in the central Willamette Valley. The gorge could see up to 9 inches of new snow from Friday night through Saturday.
East winds should die down by Monday and bring warmer air.
These totals are dwarfed by the forecast totals across the higher elevations of the Cascades in Washington and northern Oregon.