Western US to remain unsettled with more heavy rain, mountain snow in the forecast
Multiple moisture-laden storms and waves of colder air will combine to unleash a barrage of rain and mountain snow across the western United States into this week, according to AccuWeather meteorologists.
The first of two potent storms began to impact the Northwest as the weekend commenced, but forecasters say the second storm will dig even farther south. This powerful second storm will send snow levels crashing for the Pacific Northwest as well as California and Nevada.
The storm began to push into the Northwest early Sunday and will continue to pump moisture into the West. As cold air takes hold into Tuesday, this influx of moisture can bring some snow to the Vancouver area and allow snow to dip down into the hills around the Seattle and Portland areas. The best chance of a few snowflakes mixing in at sea level around Seattle is Monday night. Snow levels, where an accumulation is possible, may dip to around 500 feet.
Accumulating snow is not the most likely scenario at this point for Seattle itself, forecasters say.
The earliest measurable snow on record for the Seattle downtown area occurred more than 77 years ago on Nov. 7, 1945. The city typically gets its first accumulation in late December, while Seattle-Tacoma International Airport, located about 10 miles south of Seattle’s city center, sits about 250 feet higher in elevation than the city itself. At the airport, the earliest measurable snow on record fell on Oct. 27, 1971.
The same storm will dip southward enough to bring substantial rain and mountain snow to Northern California primarily from Monday to Tuesday. In California's Sierra Nevada mountain range, feet of snow are likely to fall at pass levels and lead to significant travel disruptions early this week.
"This storm early this week looks to be a heavy snow-producer for the northern and central Sierra Nevada," said AccuWeather Chief On-Air Meteorologist Bernie Rayno.
As the storm arrives and snow totals begin to pile up across the Sierra Nevada, travel across many popular mountain passes is likely to come to a screeching halt.
"Donner Pass is likely to receive a staggering amount of snow in a relatively short period of time this week, with several feet of snow likely to pile up," AccuWeather Meteorologist Mary Gilbert said.
There is also the likelihood of drenching rain to fall at lower elevations in Northern California from Monday to Tuesday, in cities such as San Francisco and Sacramento. There will also be an opportunity for significant amounts of rain to reach coastal locations in Southern California, including the Los Angeles and San Diego metro areas from Monday night to Tuesday night.
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It is possible that Los Angeles could receive an entire month's worth of rain from the storm on Tuesday, Election Day. The average rainfall for Los Angeles in November is 0.80 of an inch. The region desperately needs a surplus year in terms of rainfall.
During the 20-year period ending in 2020, Los Angeles has experienced a total rainfall deficit of 39.31 inches, according to retired AccuWeather Expert Meteorologist Ken Clark. The city averages 14.25 inches of rain per year.
"There has never been a drier 20-year period than 2000-2020," Clark said. "Of the 10 driest years in L.A. since records began in 1877, six have occurred in the last 20 years and four have occurred in the last decade," Clark said.
Toward the north, this storm system will spread wintry weather across a broad stretch of Canada, even at lower elevations with plenty of cold air in place. While this won't be the first flakes of the season for cities such as Calgary and Edmonton, substantial accumulations may overspread a wide swath of the Canadian Prairies for the first time this season.
"While spots in the United States may only have enough cold air for snow at higher elevations, this won't be an issue in Canada. Because of this, a broad swath of heavy, impactful snowfall appears to be in the cards to start the week," AccuWeather Meteorologist Andrew Johnson-Levine explained.
As the same storm and cold air push inland during the middle and latter part of the new week, snow is likely to pivot eastward across the mountains from northern Arizona and Utah to Colorado and Wyoming. Rain showers will reach some of the deserts, including the Palm Springs, California, Las Vegas and Phoenix areas.
The first storm that arrived right at the start of this weekend took more of a west-to-east track across British Columbia, Canada, and was able to tap into a plume of moisture from the Pacific Ocean that is often referred to as an atmospheric river. This fire hose of rain and high-elevation snow sliced southward throughout Saturday, impacting areas from Washington, Idaho, Montana and Oregon.
Power outages were rampant in Washington due to the storms early Saturday morning, topping out at nearly 500,000 across the state around 3 a.m. PDT. Snohomish County, with the third-highest population of all Washington counties, had 190,000 left in the dark during the overnight hours. The state still had over 50,000 without power as of 2 a.m. PST Monday, according to PowerOutage.US.
While heavy rain was the main story near the coast, a push of colder air will caused snow levels to drop in nearby mountain ranges early this weekend. For example, at Snoqualmie Pass, Washington, along Interstate 90, which reached into the 40s on Friday, temperatures held in the 20s on Saturday as several inches of snow accumulated. Roads became hazardous and snowpacked during this time, and that is expected to continue into the new week.
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