When Will the Train of Storms Across the Northwest US End?

By Brett Rathbun, AccuWeather.com Meteorologist

December 9,2015; 10:35PM,EST

 

 

A series of storms will continue to produce heavy rain, heavy mountain snow and strong winds across the northwestern U. S. through the weekend, ahead of a break in the pattern early next week.
Pacific storms have slammed the Northwest since the beginning of December as some locations already received more rain in the first nine days of December than they normally receive during the entire month.
On Wednesday, Washington Gov. Jay Inslee declared a state of emergency following days of hazardous weather as thousands remained with power.
Both Portland, Oregon, and Seattle typically receive just shy of 5.50 inches during all of December. Through Dec. 9, Seattle has received 5.43 inches of rain so far this month. Portland has received 7.06 inches.

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"The short-run rivers to the west of the peaks of the Cascades will be very susceptible to flooding into the weekend," AccuWeather Senior Meteorologist Alex Sosnowski said.
"The Skokomish River near Potlatch, Washington, has been hovering at major flood stage since Sunday and could approach record stage by the end of the week," Sosnowski said.
The Johnson Creek near Sycamore, Oregon, reached a record crest of 15.33 feet on Monday night. The old record was 15.30 feet set on Nov. 19, 1996.
Mild air has been in place across the region during the storms early this week causing snow levels to be well above pass level. On Wednesday, snow levels will begin to drop closer to pass level.
Rain and mountain snow will taper off during the day on Wednesday into Wednesday night as the storm system tracks into the Upper Midwest.

Snow levels are expected to be above pass level across the Cascades into Wednesday night. By Wednesday night, snow showers could mix with rain across some of the higher passes, such as Snoqualmie Pass.
The strongest winds on Wednesday will be concentrated across the eastern portions of Washington and Oregon with gusts up to 60 mph possible.
Winds will also pick up across the northern Rockies with gusts to 60 mph from Great Falls, Montana, to Cheyenne, Wyoming, and the Colorado Rockies. Gusts across northwestern Montana and southeastern Wyoming could reach hurricane force.

The next system will crash into the Northwest on Wednesday night through Thursday. This storm contains much-colder air, causing snow levels to drop near or below pass levels. The heaviest rain from this system will be confined across northern California and southwestern Oregon.
"Colder air will move into the Northwest on Wednesday night into Thursday, causing snow levels to fall across the Cascades," AccuWeather Meteorologist Dan Pydynowski said.
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Rain will continue to soak much of the lower elevations of the Northwest, but the intensity of the rain will be less compared to the storms earlier in the week.
"Snow levels could be as low as 3,000 feet at times on Thursday across the Cascades," Dan Pydynowski said. "This could impact travel with some snow down to pass levels, including Snoqualmie Pass."
Dan Pydynowski also added that snow levels will drop across the Sierra Nevada on Thursday and could impact travel at Donner Pass along Interstate 80.
A sinkhole opened up on a road in Gresham, Ore., just west of Portland, on Dec. 7 after heavy rain. (Facebook Photo/City of Gresham)
"A few yards of snow will bury the high country of the western slopes of the Cascades by the weekend. This also includes Whistler Ski Resort, where the storm train will be an all-snow event," Pydynowski said.
Snow will be measured in feet across the Sierra Nevada.
"The snow could accumulate a couple of feet in the highest peaks of the central Sierra, the part of the range that needs mountain snow the most for ski resorts and water resources," AccuWeather Meteorologist Brian Lada said.
Periods of rain will continue across the Pacific Northwest on Friday with snow across the higher elevations.
Additional storms are expected to pass across the Northwest each day this weekend before a possible break in the storms early next week.
High pressure is expected to drop down from British Columbia and bring dry conditions to much of the western U.S. on next Monday into Wednesday. While a few areas of rain or snow are possible, precipitation amounts are expected to be low during this period.