Portland, Oregon. – Arctic blasts that sent the Pacific Northwest into an icebox mixed with strong Pacific storms late Thursday and Friday, creating severe ice storms in northwestern Oregon and western Washington, including Portland and the Willamette Valley. Brings the recipe… Even parts of Seattle and the Puget Sound area threaten to halt vacation travel and knock out power for thousands.
Winter Storm Warnings are in place for the Portland and Willamette Valley areas for a myriad of winter conditions, including freezing rainfall of 0.2 to 0.4 inches, gusts of 55 mph near the Columbia River Gorge, and wind chills that drop to zero. is issued in
Ice storm warnings extend to areas of Eugene and Corvallis, with even greater freezing rainfall of up to half an inch, considered potentially “catastrophic” levels, while western Washington and Seattle have their own Stay on the winter storm watch for possible snow and freezing rain problems.
Cold temperatures in eastern Washington dropped to near zero or below Thursday morning as Arctic air continues to pool in the region, setting temperatures in northern Oregon and western Washington in the teens and twenties. and in the single digits in eastern Oregon.
However, the next weather system heading northwest from late Thursday through Friday is a much milder storm off the Pacific Ocean.
Cold air is now trapped at the surface, so precipitation could start as snow. As the battle between the intrusion of warm air and the stubborn freezing air at the surface takes place over several hours, precipitation can potentially turn into long-term freezing rain, allowing for significant accretion.
What is ice rain?
FOX Weather meteorologist Britta Merwin said, “Sometimes ice is worse than snow, especially when traveling on roads.
Freezing rain is expected in many parts of the Pacific Northwest, continuing late Thursday night through Friday afternoon or early evening. In the Columbia Gorge and eastern Willamette Valley, it could last until Saturday, with canyon ice accumulation reaching nearly an inch.
The Portland area and southwestern Washington could see significant ice accretion in the range of 1/10 to 0.5 inches, while the Seattle area and northwestern Washington could see light but potentially impactful ice accretion. Some glaze is expected.
What is ice storm?
Ice deposits of 1/4 to 1/2 inch are considered “disruptive” and make the roads very slippery, so many power outages and damage to trees are to be expected. Deposits of half an inch or more can cause massive power outages, downed trees, and dangerous moving conditions, causing catastrophic damage.
Traveling along Interstate 5 from central Oregon to the Canadian border can be difficult during an ice storm, when the icy glaze on the pavement thwarts any hope of traction.
How much ice does it take to knock out power and damage trees?
Both Seattle and Portland airports can experience significant weather-related delays during and immediately after ice storms. Planes are covered in ice glaze, airports are grappling with busy deicing operations, and more storms in the east this week add to the national air travel predicament.
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Portland’s airport was closed for several days during the 2004 ice storm, while Seattle’s Sea-Tac Airport was closed for more than a day during a historic ice event in January 2012.
Eventually, the warm air will win the battle, and cold rain will gradually turn to normal later on Friday as temperatures climb into the 40s.
Once the cold air is swept away, the weather pattern will reverse, with above-average temperatures reaching the high 40s to 50s over Christmas weekend, followed by higher snow levels and heavy rains the following week.
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Unique setting makes Portland susceptible to prolonged ice storms
Subzero or near-zero temperatures lurking on the eastern side of the Cascade Range create areas of high pressure due to the high density of cold air. On the other hand, when a deep low pressure system approaches the coast from an approaching storm, the intense pressure difference causes strong easterly winds to blow through gaps in the cascades.
Such gaps include major passes such as the Fraser River Valley in British Columbia and Snoqualmie Pass in Washington.
The largest conduit channeling Arctic air from the east into the coastal valleys is along the Columbia River Gorge, which straddles the Washington-Oregon border and flows into the eastern suburbs of Portland.
Gusts of wind passing through the canyon can reach 50 to 70 miles per hour, with some of the strongest events gusting winds in excess of 100 miles per hour. Not only do these winds blow over the eastern Portland area in gusts of over 50 miles per hour, but they also act like icy blow dryers, pushing the altered Arctic air into the lower elevations of the Willamette Valley continuously. Spill on
When the constant warm Pacific rain falls on this layer of frozen air trapped near the ground, it freezes on contact, creating freezing rain.
Depending on the depth of the cold air east of the mountains and the strength and speed of the approaching storm, the howling easterly wind could last for hours, if not days, breaking the Portland area into a thick and widespread storm. lead to ice accretion. Power outages occur as trees and power lines bend under the weight of the ice, making roads impassable.