First Alert Weather Day: Flurries, ice pellets, then freezing rain tonight
It’s a bitterly cold and windy day across the Portland metro area; our coldest day in about 8 years (since Feb 2014)! A modified arctic airmass has spread out of the Columbia River Gorge and into the lower elevations of NW Oregon and SW Washington. Meanwhile, a wet weather system is approaching and will ride over the top of that shallow, cold airmass tonight. Temperatures in the lower 20s right now should hold steady through tomorrow morning, then SLOWLY rise through Saturday. The entire metro area and likely the valley down to Salem, will remain frozen through sunrise Saturday.
This sets us up for an ice storm tonight, with light freezing rain continue off/on through Saturday morning. As the air starts to warm up high, the first precipitation may fall as snow or ice pellets this evening, but anything that falls after 7-8pm should be as liquid rain that freezes on contact with objects or the ground. Roads turn icy quickly with this setup and they remain icy all the way through Saturday morning.
We expect ¼” to ½” ice glazing in the western valleys tonight through Saturday morning, with most of that tonight. Freezing rain will be much lighter and just come and go tomorrow and we’ll be mainly dry Friday night into Saturday morning.
Saturday is the difficult part of the forecast…as a much wetter system gives us a rainy day. A real soaker on Saturday. But our gut feeling is that central/east metro near the Columbia River will remain frozen through much of the day, accumulating a thick layer of ice. Up to 1″ of ice glazing is possible there for more power outages and damage to trees. For south & west metro, plus Clark county, we expect temperatures to rise above freezing Saturday. That ends the storm in those areas…the liquid rain just stops freezing.
By Saturday evening (Christmas Eve), a warm southerly wind should have punched through the cold air all areas west of the Cascades except right along the Columbia River close to the Gorge. Hopefully even those east metro areas go above freezing.
Sunday looks mainly dry, then wetter in the afternoon and all of the metro area should be above freezing on that day.
COLUMBIA RIVER GORGE: This area will not see a warming westerly wind until EARLY NEXT WEEK. The result is a long duration ice storm tomorrow through at least Sunday, although not much freezing rain falls Sunday. Another surge on Monday could bring more freezing rain out there, if temperatures remain cold enough. I-84 WILL REMAIN FROZEN THROUGH THE GORGE THROUGH SUNDAY.
We will be in a wet and occasionally windy pattern all next week as several Pacific weather systems move onshore. Lots of rain, but mild.
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