ICE STORM ARRIVES LATE THURS: Getting a lot of questions about the pending ice storm for n.w. Oregon & s.w. Washington. This thread should answer some q’s, including:
1) When will it turn icy?
2) How much ice will accumulate?
3) Roughly when will it thaw out?
#PDX #ORwx #WAwx
1) When will it turn icy?
2) How much ice will accumulate?
3) Roughly when will it thaw out?
#PDX #ORwx #WAwx
Between this afternoon & eve, modified arctic air will surge through the Gorge & spread across the Portland metro area. Temps will drop into the 20s & teens / wind chills in the single digits & maybe below zero. Cold air spreads across western valleys & coastline tonight.
Ice will begin to accumulate late Thurs. By Friday A.M., most surfaces will be glazed over. Populated areas up & down I-5 corridor could pick up ~ 1/10-1/4” of ice. Lots of power outages expected. Pockets of Coast Range, metro area, Cascades & Gorge could see 1/4-1/2”+ of ice.
Simply put: areas to the north exposed to the cold east wind will be below freezing for a longer period of time, so expect a longer period of freezing rain / greater accumulations. The worst of it should occur in the Gorge. More on that later in the thread.
First to thaw out should be locations north of Newport (central/south Coast shouldn’t see much action). North Coast can expect to thaw out around Friday morning when the southerly wind warms temps up. Southern Willamette Valley: mid morning to midday Friday.
Next to thaw should be part of the central Willamette Valley, and timing should be between Friday afternoon & evening. Salem will be borderline.. maybe not till the nighttime. Finally, the south & west metro area should begin to thaw between Friday night & Saturday morning.
It gets very tricky in the central & east metro area. If we get a decent southerly wind, thawing should begin Saturday afternoon. If the wind is light and still out of the east, frozen surfaces could carry into the evening. Warm air should erode away the remainder of cold air.. 
between Saturday night & early Sunday. Finally, the Gorge will be last to thaw out. Major winter storm setting up. Around 4-6” of snow between Thursday night & Friday, switching over to freezing rain Saturday. Upwards of 1/2-1.5” of ice accumulation this weekend, on top of snow.
Driving thru the Gorge this weekend will be somewhere between treacherous and impossible. Expect to be frozen through most of holiday weekend.
Here’s a look at our 7 day forecast for the Portland/Vancouver metro area. Greatest impacts expected Thursday evening - Saturday. #PDX #ORwx #WAwx
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