Typically within the climate enterprise, every part occurs in a brief interval.
That is such a interval.
We’ll expertise:
1. The coldest temperatures in a number of years on each side of the Cascades
2. A freezing-rain storm significantly within the Gorge, the northern Willamette Valley, and south of downtown Seattle.
3. Highly effective easterly winds reaching hurricane power within the Columbia Gorge and the passes.
4. A fast warm-up this weekend, with the return of typical rain and delicate situations.
Stage 1. Arctic Air
Jap Washington is already very chilly, with some temperatures getting beneath zero final evening. Western Washington temps are properly beneath regular.
As an instance, listed here are the low temperatures this morning. In western Washington, primo chilly air is pushing southwestward via the Fraser River Valley of NW Washington.
Tonight even colder air will transfer in, coupled with good radiational cooling to area as a result of the clouds are scaling down aloft. Temperatures will drop as little as the teenagers away from the water in western Washington.
Stage 2: Robust Easterly Winds
This massive strain distinction will drive highly effective easterly (from the east) winds via the Cascade passes and significantly the Columbia River gorge. Winds from Cascade Locks to Troutdale within the Gorge might hit 60+ mph–and this can be chilly Arctic air from japanese Washington.
Robust easterly winds will even descend the western slopes of the WA Cascades, with highly effective gusts from North Bend to Enumclaw, with winds accelerating to the west down the Strait of Juan de Fuca. (see wind gust map at 10 AM Thursday). Greens and blues are the strongest winds.
Stage 3: Freezing Rain
We may have chilly air in place. After which a Pacific frontal system with a lot of moisture will strategy late Thursday night into Friday morning. A frontal system that can transfer in hotter air aloft.
Right here is the precipitation forecast for 1 AM Friday morning–plenty of moisture.
Now, at first, the precipitation will fall as snow all through the area.
However that will not final because the entrance surges in heat air aloft from the south.
And this units up a freezing rain scenario. Let me clarify utilizing the determine beneath.
Initially, (proper aspect of determine) the ambiance is chilly sufficient for snow via depth (nearly all precipitation in our area through the winter begins as snow aloft)
However because the entrance approaches, above-freezing air pushes in aloft and the snow begins to soften into water droplets.
Initially, the chilly air is deep sufficient that the melted droplets refreeze into little ice spheres: that is sleet.
However finally, as the nice and cozy air aloft deepens sufficient, the water droplets aloft should not have time to refreeze however quiet down sufficient to grow to be supercooled water...water that’s liquid however nonetheless beneath freezing.
Then, when this supercooled water hits the chilly floor (and it is going to be chilly), it freezes on contact…producing freezing rain!
The most recent European Middle forecast for the buildup of freezing rain is proven beneath.
Via 3 AM Friday, the freezing rain whole is heavy within the coastal mountains and begins to unfold inland.
Via 4 PM Friday, you possibly can see substantial freezing rain totals over south Puget Sound, the Columbia Gorge, and northern Willamette Valley.
And thru 4 AM Saturday, the ice piles up within the Columbia Gorge.
On Saturday, all of it turns to rain.
Anyway, this appears to be like like a significant freezing rain occasion for the area. The airways should be prepared at SeaTac and significantly Portland, with Friday morning being significantly problematic.
