Updated Dec. 31, 2019 5:44 PM
Unrelenting storms will pound the northwestern United States well into 2020 and escalate the risk of flash flooding, mudslides and avalanches as ski resorts continue to be bombarded with heavy snow.
"Expect rounds of strong winds from the storms with the potential for power outages," AccuWeather Senior Meteorologist Brian Thompson said.
"Snow levels will vary with each storm," Thompson said. "At times rain may reach to pass levels, and at other times, snow may dip to just above sea level through next week."
This satellite loop from Tuesday, Dec. 31, 2019, shows an atmospheric river taking aim at the northwestern United States. (NOAA / GOES-West)
The main thrust of the storms through this weekend will focus on British Columbia and western Washington. A general 3-6 inches (80-150 millimeters) of rain will fall, but an AccuWeather Local StormMax™ of 12 inches (300 millimeters) is likely on the west-facing slopes of the Olympics, Cascades and Coast Mountains.
The cumulative effect of each storm will make the hillsides unstable. With each round of drenching rain, the risk of mudslides and other debris flows will increase over the lower elevations.
Episodes of heavy rain in low and intermediate elevations will cause streams and rivers to run high with the risk of flooding.
Meanwhile, above the passes over the high country, a heavy load of snow, on the order of 3-6 feet (1-2 meters) with local amounts to 9 feet (3 meters) will pile up over the next week. The snow load from each storm and periodic gusty winds can make the snowpack unstable with an increasing risk of avalanches.
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Even at intermediate elevations, heavy snow with some storms and a wintry mix and rain with others can also heighten the avalanche risk.
Intermittent rain and snow will progress farther inland over eastern Washington and Oregon, including areas often sheltered by precipitation due to the proximity of the Cascades. Periodic, locally heavy snow will fall over the Blue Mountains and the various ranges that make up the northern Rockies into next week.
The first weather system of the barrage will continue to affect the region through Wednesday night. Rain and snow will push southward into Oregon as snow slides southeastward over the Intermountain West.
This storm has the potential to bring several inches of snow to Salt Lake City on New Year's Day to Wednesday night.
A second storm will waste no time rolling in from the Pacific later Thursday to Friday. This storm is likely to bring heavy precipitation and difficult travel over the passes in the Washington Cascades. Snow levels will start off low, near 1,500 feet Thursday afternoon, before rising.
The heavy precipitation will be accompanied by gusty winds late this week. Gusts averaging 25-50 mph are expected to buffet the Washington coast with more powerful gusts to near 60 mph (97 km/h) likely in British Columbia.
A storm during Friday night and Saturday may catch up to the Friday storm, and little to no break is anticipated in unsettled weather over British Columbia. Washington may only catch a few hours’ break between the storms.
The weekend storm is likely to be the most potent of the bunch especially in terms of wind. Gusts approaching 75 mph (120 km/h) are predicted along the British Columbia and northern Washington coastline, and gales may exceed 60 mph (97 km/h) over the passes.
As this storm progresses inland, gusts approaching 90 mph (145 km/h) are possible over the passes in Montana and the foothills east of the Rockies from Montana to southern Alberta.
The unrelenting onslaught of storms will not end after this week, but the origin and nature of storms may evolve as January progresses, according to AccuWeather meteorologists.
"It is possible that a shift in the storm track develops later next week where storms move from north to south across British Columbia and the northwestern U.S. instead of straight in from the west off the Pacific Ocean," Thompson said.
"As this occurs, enough cold air may sink southward to allow snow to fall at very low elevations along the coast," he added.
It is possible that a storm or two will bring rare snow down to near sea level during the second and third week of January.
Download the free AccuWeather app to check the forecast in your area. Keep checking back on AccuWeather.com and stay tuned to the AccuWeather Network on DirecTV, Frontier and Verizon Fios.
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