Probability of rain enters San Francisco Bay Space forecast
A late-summer storm system over the Gulf of Alaska will move south in the coming days, bringing a chance of rain to water-starved, wildfire-prone Northern California. It may potentially deliver a sprinkling to the San Francisco Bay Area and wet many of the wildfires that have burned for weeks, the National Weather Service said.
While the forecast will likely shift later this week, as of Tuesday morning weather models showed the window for rain in the Bay Area running from Saturday afternoon into Sunday.
“The greatest chance is in the North Bay,” said Jeff Lorber, a meteorologist with the weather service.
The chance for rain stands at about 20% for Napa and Sonoma counties, 15% for San Francisco and 10% in the South Bay, Lorber said.
Latest Climate Prediction Center outlook shows high probability of below normal temps and above normal predict this weekend and early next week in the PacNW as a trough moves onshore. Might some premise reach the #BayArea?? We’re keeping an eye on it. #CAwx pic.twitter.com/PU3YfRO01j
— NWS Bay Area (@NWSBayArea) September 14, 2021
The Pacific Northwest is expected to receive a soaking of rain Friday into Saturday. It’s unclear how well the system will hold together as it pushes into the water-starved Golden State, and Lorber said these storms often fall apart as they move south.
“It will reach the Pacific Northwest and, depending on how deep this trough becomes, will determine how far south the rain goes,” he said.
California is desperate for rain as reservoir levels sink to record low levels and the vegetation on the ground is parched and highly flammable after two consecutive dry winters.
The Dixie Fire, 250 miles northeast of San Francisco, has been burning for two months and is approaching 1 million acres. The Caldor Fire led to evacuations in South Lake Tahoe. Both of these blazes could benefit from moisture.
“It is a low-confidence forecast, but the best chances would probably be over the Dixie Fire over the Caldor Fire,” said Emily Heller, a forecaster with the weather service’s Sacramento office. “The further south we go, the less probability there is. The best chances would most likely be in the Saturday to Sunday timeframe, and as of right now we’re not expecting heavy rain or thunderstorms.”
Cooler temperatures are expected later this week with rains spreading into the area Friday night and Saturday. Storm total #rainfall through the weekend is expected to range from nearly 2″ across the N Del Norte mountains to a few hundredths of an inch in S Lake County. #CAwx pic.twitter.com/Nw686Ou4Vu
— NWS Eureka (@NWSEureka) September 14, 2021
The far northwest corner of California is expected to see the most rain over the weekend event; up to 2 inches is possible in the mountains of Del Norte County. Crescent City is forecast to see 1.36 inches, Yreka 0.54 inch and Shasta 0.42 inch, the weather service’s Eureka office said.
The forecast is likely to change in coming days as weather models are often in disagreement over the first storms of the rainy season.
“With these early season storm systems, often the models are overly optimistic,” said Lorber, noting that even the slightest bit of drizzle would still be beneficial with the dry vegetation. “Any rain is good news with the really dry fuels. Moisture is really desperately needed, as we have near-record dry fuels.”
