First snow, then ice, now freezing rain?

First snow, then ice, now freezing rain?

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First snow, then ice, now freezing rain?


Forecasters are saying the possibility of freezing rain is growing for Thursday in the inland areas of Southwest Washington and Northwest Oregon.

"A strengthening upper low over the Gulf of Alaska will bring a threat for freezing rain reaching the coast late on Thursday morning and then spreading inland Thursday afternoon and evening."

So what exactly does it mean for us? Here is the text of the latest forecast discussion:

The most likely scenario brings a rather short lived event with the primary focus across an area mainly north of Wilsonville. There would be a few hours of ice accumulation followed by gradual warming above freezing. Amounts of ice accumulation would most likely be two tenths of an inch or less... typically not enough to produce major damage.

However... there is a fair amount of uncertainty with this system in both timing and whether the bulk of the Willamette Valley receives the freezing rain. The main unknown at this time centers around how quickly the lower level cold air mass and morning fog and low clouds break up... and whether southerly winds above the 1500 foot level drop to the surface and scour out the cold pool like most models want to illustrate. If the cold air does not scour out... the full potential of this event could materialize with valley locations remaining under the influence of a cold pool for longer than a couple hours. If so... then somewhere between one quarter and one half an inch of ice may produce notable damage to trees and power lines plus the obvious threat to Road surfaces.

Even under the worst case scenario... feel all areas will warm above freezing by later Thursday evening. Would expect the Columbia Gorge to be the last place to warm... possibly not until later Thursday night and Friday morning.

This is a difficult forecast as weather models rarely handle the vertical temperature erosion accurately. Please continue to follow the latest forecasts as this situation evolves.