Break coming for US West Coast following potent storm into Sunday night
The caboose in a long train of storms is in sight along the Pacific coast from Washington to Northern California. But AccuWeather meteorologists warn that the last rounds of rain can trigger flash flooding and mudslides, and lowering snow levels over the Cascades and Sierra Nevada can stall travel into Sunday night. Big waves will continue to pound the California coastline.
Rain of varying intensity from the final storm in the series will pour down and continue into Sunday from western Oregon to Northern California and western Washington. Rain totaling 4-8 inches will occur mainly from southwest Oregon to Northwestern California. The AccuWeather Local StormMax™ rainfall of 18 inches can be approached over the west-facing slopes of the Coast Ranges, Siskiyous and Oregon Cascades.
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Rainfall of this magnitude, on top of saturated ground from prior storms, is more than enough to lead to flash flooding of urban areas and small streams, mudslides and road washouts.
Enough rain will fall to make roads slick in at times in Seattle, San Francisco and Portland, Oregon, as well as Sacramento, California, Eugene, Oregon, and Astoria, Washington.
Winds will become strong enough from Northwestern California to southwestern Washington to tip trees over in the saturated soil and cause large tree limbs to break in some cases. Both can trigger sporadic power outages. Winds from the west will help to drive large swells toward the California coastline into Monday. The big breakers will create dangerous surf and strong rip currents for Southern California beaches.
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Snow levels that were initially well above Donner Pass, California, into Saturday night, have plummeted on Sunday, AccuWeather Meteorologist Haley Taylor said.
"A quick burst of snow into Sunday night can bring 6-12 inches of snow over the northern Sierra Nevada," Taylor said, "It may end up closer to 6 inches over the pass, but that is more than enough to cover roads and potentially hinder travel."
Blizzard conditions are possible for a time over Donner Pass into Sunday night, which could shut down Interstate 80.
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Farther north, especially the Washington Cascades, snow levels will hover at or just below the passes, and the snow will pile up into Sunday night with a general 6-12 inches of snow likely, Taylor added.
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As the storm pushes inland, spotty snow, especially over the mountains in eastern Oregon, Idaho, western Montana, and the northern parts of Nevada, Utah, and Colorado, will ramp up from Sunday to early Monday. A general 6-12 inches of snow will fall over the higher elevations, with more possible on some of the ridges, peaks and ski resorts. All or mostly rain will fall over the lower elevations in this zone, including Boise, Idaho; Salt Lake City and Spokane, Washington.
The storm and its rain and mountain snow will avoid nearly all of Southern California and southern Nevada. Soil conditions will remain dry as a result. As the caboose storm moves inland, high pressure will build over the Great Basin early this week.
The setup for Southern California is likely to trigger a Santa Ana with northeast winds from Tuesday to Wednesday, they may begin as a Sundowner event with northerly winds Monday night.
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Even though the wind event may not be too strong, it will substantially increase the wildfire danger. As a result, the use of open flames for cooking and construction, and fireworks for celebration activities is not recommended.
The strongest winds may be easing up for the parade in Pasadena, California, on New Year's Day morning. Downtown Los Angeles is often sheltered from Santa Ana winds due to the bowl-like basin the city sits in.
A pause in the storm train is coming for areas from western Washington to Northern California, spanning Monday to most of Tuesday.
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The storm break will allow cleanup operations to commence and provide decent travel conditions in the region.
The next storm will likely bring low-elevation rain and mountain snow by New Year's Day to areas as far south as the northern tier of California.
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Additional storms with some rain and mountain snow are likely to follow later in the week, but they do not appear to be as potent or carry as much moisture as the storms from the latter part of December.
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