A cold front originating from the Gulf of Alaska swept into Northern California, bringing rain and snow over the weekend. The storm introduced a mass of cold air into the region, resulting in below-normal temperatures from Saturday through Monday.
“Impressive late-season low-pressure system will bring a short, sharp hit of cold rain (and mountain snow above ~4k ft) this weekend,” tweeted UCLA climate scientist Daniel Swain. “Nearly everywhere in NorCal should see good soaking, with lighter showers into SoCal. This will be quite a cold system by May standards.”
Temperatures across California during this period are expected to be 5 to 20 degrees below normal.
Far Northern California, including Del Norte and Humboldt counties, experienced rainfall rates of up to 0.5 inches per hour overnight, with snow levels in the coastal range dropping as low as 2,500 feet. Inland valleys in the area may see near-freezing temperatures on Saturday and Sunday nights.
The Bay Area received significant rainfall on Saturday morning, with downtown San Francisco measuring 0.59 inches by 11 a.m., close to the monthly average for May. Santa Rosa, Oakland, and San Jose also received varying amounts of rainfall.
“By early Saturday evening, the rains should be starting to wrap up. It’s pretty much going to be a one-day event,” said Alexis Clouser, a forecaster with the weather service’s Bay Area office, adding that Sunday is expected to be dry in the Bay Area.
Rain is forecasted for most of the Central Valley over the weekend, with Sacramento, Stockton, Modesto, and Fresno expected to receive significant rainfall. Snowfall predictions include 18 to 24 inches in Lassen Volcanic National Park, 8 to 12 inches at Donner Pass, and varying amounts at other mountain passes.
The storm is anticipated to weaken as it moves into Central and Southern California, with lower rainfall totals expected in these regions compared to Northern California. Light rain was already falling in Monterey County and was expected to reach San Luis Obispo County by the afternoon.