Two storm systems moving out of the Gulf of Alaska are on track to bring the first substantial snow of the 2017-18 winter season to the Sierra Nevada, starting Friday, and widespread rainfall across the Bay Area over the weekend.

Forecasters said Monday that gusty winds and 1 to 2 feet of snow are likely Saturday and Sunday along California’s main mountain passes, including Donner Pass near Lake Tahoe, Tioga Pass at Yosemite, Ebbetts Pass and Carson Pass, with perhaps a foot along the shoreline of Lake Tahoe this weekend.

These same storm systems that are forecast to turn the Sierra Nevada peaks white, and perhaps close higher-elevation mountain roads, are also expected to bring roughly half an inch of rain from Friday to Sunday in San Jose, up to 1 inch to San Francisco and the East Bay, and 1.5 inches or more to the Santa Cruz Mountains, Big Sur and the North Bay.

That’s raising concerns over the areas of Napa and Sonoma counties that are still recovering from this month’s historic fires. There’ s a potential for ash and debris flows in the areas that burned. “If you get a lot of rain on a steep incline, that stuff can move. It can block drains and culverts and increase the risk of localized flooding.”

The season’s first big storm comes after record rainfall last winter ended California’s historic drought. For the ski industry, which suffered through four dry years between 2011 and 2015, a foot or two of snow the first week of November is the perfect Halloween treat.

“Everyone is getting really excited and gearing up,” said Michael Reitzell, president of the California Ski Industry Association. “If it’s a good normal season, this is about the time when we start to see the early snowfall and the temperatures drop so our resorts can begin snow-making.”

Last winter, a relentless series of massive atmospheric river storms drenched California, flooding downtown San Jose along Coyote Creek, wrecking the spillway at Oroville Dam, washing out roads and bridges in Big Sur and ending the state’s historic drought.

Typically in November most of California ski resorts open only a few runs, mixing in natural snow with snow they create with large snow-making machines. As storms continue, they are able to open more runs and build a larger base.

Mercury / Crickey Conservation Society 2017.

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