Cold storm to blast Sierra with snow level dropping as low as 1,000 feet

Caltrans shared pictures of winter conditions on Twitter and warned drivers to proceed cautiously. Caltrans shared pictures of winter conditions on Twitter and warned drivers to proceed cautiously. Photo: Caltrans Photo: Caltrans Image 1 of / 4 Caption Close Cold storm to blast Sierra with snow level dropping as low as 1,000 feet 1 / 4 Back to Gallery

A quick-moving storm known as an "inside slider" will deliver a chilly blow to the northern Sierra Nevada early Thursday morning, with a couple inches forecast for elevations as low as 1,500 feet and a dusting likely at 1,000 feet. Snow flurries are possible through Friday.

As opposed to the moisture-rich storms that come off the Pacific, this system will fall directly from the north and spray mountainsides with dry, powdery snow.

"This sort of storm makes more snow out of less precipitation," explains Shane Snyder, a meteorologist with the National Weather Service in Reno. "It's so cold you don't need as much precipitation to make snowfall. If you got like a tenth of an inch of precipitation you could get two or more inches of snow.

Temperatures will drop into the high teens and low 20s overnight, and the Tahoe Basin likely won't get out of the 20s on Thursday.

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Three to six inches of snow is forecast for the basin, and Snyder says, "There could be a few spots that could reach as high as 6 to 10 inches in higher terrain if we get a strong band."

Mountain passes will see five to eight inches of snow and motorists driving between the Bay Area and the Sierra should be prepared for snow-covered roads, slippery conditions, reduced visibility, travel delays and chain control Thursday morning through Friday night, warns the National Weather Service office in Sacramento.

The storm is expected to first hit between 4 a.m. and 6 a.m. Thursday.

Friday night will see temperatures drop below the freezing mark and skies will clear Saturday afternoon. A weak system might move across the northern Sierra Saturday night, but Snyder says it's unlikely to bring more snow.

"The next chance for significant snowfall will be Monday," he says.

Left: A photo of an Incline Village stop sign in February 2017 shows snow piled up amid a winter marked by potent storms. Right: The photo on the right shows the same location in February 2018 amid a year marked by low snowfall. less Left: A photo of an Incline Village stop sign in February 2017 shows snow piled up amid a winter marked by potent storms. Right: The photo on the right shows the same location in February 2018 amid a year marked ... more Photo: Martin Gollery Photo: Martin Gollery Image 1 of / 5 Caption Close Tahoe before and after: February 2017 and February 2018 1 / 5 Back to Gallery

The Sierra is desperate for snow this season, and as of Feb. 20 the snowpack was 20 percent of average.

A high-pressure ridge has been parked along the West Coast for much of the 2017-18 winter, acting like an invisible wall and blocking moisture-rich storms in the Pacific Ocean from reaching land.

In the first two weeks of February, the Sierra only received light dustings of snow.

The recent spate of storms is welcome but they have been weak and won't help to significantly bolster the snowpack that's one of California's most important water sources with its spring and summer runoff feeding rivers and reservoirs, watering crops, filling bathtubs and water glasses.

On average the Sierra snowpack supplies about 30 percent of the state's water needs.

Because of last year's record-breaking wet winter, the reservoirs are full, but this year's scarcity of snow is raising concerns that the state is heading into another drought pattern.