Snow On Bay Area Hilltops, Frost Possible As Cold Front Arrives

SAN FRANCISCO — The recent stretch of pleasant weather will give way to a cold front that will send overnight temperatures tumbling and could bring snow to the foothills by next weekend, according to the latest forecasts. In the Sierra, a storm is brewing that some experts warn could outperform some of last year's biggest snow events.

The National Weather Service said the cold front would move southward over the Bay Area through Monday evening, cooling temps by at least 10 degrees by Tuesday morning. Communities that may see lows dip into the 30s include Concord, Fremont, Hollister, Livermore, Napa, San Jose, Santa Rosa and Sunnyvale.

Lows may lean more frigid in the North Bay, potentially dropping to the mid-30s, prompting the National Weather Service to issue a frost advisory covering large swaths of Marin, Napa, Solano and Sonoma counties.

"Portions of the North Bay interior Valleys and Mountains have a moderate to high probability (35-70 percent) of reaching 36 degrees or colder, and therefore considering both cold temperatures and societal impacts a Frost Advisory was issued for these areas for late tonight into Tuesday morning," NWS Bay Area forecasters said Monday. "This may be a borderline situation for some valley locations it will likely dip to near/below 36 at least in pockets towards morning. Portions of the East Bay may also approach Frost Advisory thresholds, but confidence and probabilities here are a bit lower outside of the higher terrain."

While some area receive rain midday Monday, forecasters expect a ridge of high pressure will keep things mostly dry and cool through at least Wednesday, ahead of an unsettled pattern that looks to bring another rainy stretch to NorCal and potential snow in mountain ridges. According to CBS Bay Area, snow levels may dip as low as 1,000 feet by Saturday night, opening the door for some accumulations in the foothills.

"This is a colder system and snow levels will lower this weekend," the weather service said. "Some ridgetop snow accumulations are possible, with the greatest potential for this over the Santa Lucias and perhaps portions of the Diablo range."

At higher elevations, forecasters are preparing for what could be the Sierra's biggest snowstorm of the year, expecting 5 to 12 feet of snow in areas above 5,000 feet. More than 7.5 feet of snow could hammer Donner Summit over 48 hours, and the weather service warned travel over the passes would be "nearly impossible" from Thursday through the weekend.

As for the rain, forecasters expect 1 to 2 inches of precipitation at low elevations for most of the Bay Area between Thursday and Sunday, with higher totals likely in coastal ranges.