A pair of powerful storm systems will crash into the West Coast through early next week unloading several inches of rain in the lowlands and feet of mountain snow across California.
The first storm, arriving in California on Thursday and Thursday night, has already plastered parts of the Pacific Northwest with snow. It’s diving southward and will deliver blinding mountain snow in the Sierras in addition to welcome rain in lower elevations, including the San Francisco Bay area. It’s a quick-hitter that will be followed-up by notably cold weather that could set records.
A second winter storm drops into the region this weekend that will be almost a carbon copy of the first event.
The storm dropping into California has it roots in the Pacific Northwest, where it has already dropped snowfall down to low elevations.
One to three inches fell in Seattle on Tuesday night into Wednesday morning. Areas north of the city picked up as much as 3 to 7 inches, and flakes were falling in the area again Thursday morning amid an icy commute.
Near the Oregon-Washington border, snow fell and stuck all the way to the coast Wednesday night. The National Weather Service office in Portland shared a scene of a snowy Highway 101 in Seaside, Ore., to the northwest. Up to 2 to 4 feet of snow has fallen in the Cascades during the 48 hours ending Thursday.
Thursday’s heaviest rain is forecast to focus on the San Francisco Bay area southward to south of Monterey, ultimately making it into parts of Southern California around Los Angeles by Friday morning. The most rainfall will be along and immediately behind a cold front dropping through the state. This activity lasts about 6 to 8 hours in most spots before precipitation turns more showery.
Totals from this batch of rain are mainly in a half-inch to inch range right along the coast, with lesser amounts in valley areas inland. Higher precipitation totals are likely in the Sierra Nevada mountains, with much of that falling as snow.
“At the peak, very heavy snow rates in excess of 3 inches per hour are forecast, leading to dangerous or impossible travel,” wrote the Weather Service.
Snowfall totals as high as three feet are anticipated along the Sierra crest by midday Friday. Heavy snow, in addition to strong winds, likely leads to backcountry avalanches. Strong winds may gust upward of 65 mph at resort base level and 100 mph at mountaintop peaks.
On Friday, areas of moderate to heavy snow will push eastward into the Intermountain West and Rockies, where a generally snowy November has just wrapped up.
The cold front sweeping south over California will allow snow levels to drop, in some cases to not far from sea level, but limited moisture on the front’s backside should prevent accumulations from occurring in the hills around the San Francisco Bay region.
That won’t stop the cold.
A handful of record cold high temperatures are forecast for Thursday, particularly in Northern California. Highs along the north coast may not top the mid-40s. Locations near Mount Shasta may see highs hover around freezing.
Record to near-record cold is also a good bet Friday morning, from Washington state into Northern California. A forecast low of 26 degrees in Seattle would threaten the Dec. 2 record of 25 degrees from 1985. Tahoe City is expected to fall to 4 degrees Thursday night, shattering the existing record low of 10 degrees from 1968.
Napa Valley is among areas under a freeze warning Thursday night. Temperatures there are expected to fall into the upper 20s, with frost likely. Freeze warnings include portions of the North Bay, interior Monterey and the eastern Santa Clara hills to the north and south of San Francisco.
Another storm system is slated to drop out of the Gulf of Alaska and into the Pacific Northwest and toward California this weekend. It will bring a new bout of stormy weather to the region.
“Similar amounts of rain and higher elevation snow look possible with this system as compared with the current one,” wrote the Weather Service in Sacramento in a Thursday morning discussion.
By the end of the weekend, and combining both storms, some spots along the central California coast may pick up two to four inches of rain. This could lead to isolated flash flooding or landslides.
Beyond that, it seems that the weather may stay damp and unsettled at least until around Dec. 10. The storminess is welcome news in a region still held strongly in the grips of multiyear drought.
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