First actual rain of the season coming to San Francisco Bay Space. How a lot will fall?
The first rain of the season is expected in the San Francisco Bay Area this weekend.
While only a drizzle can be seen in some places, any moisture is beneficial after two consecutive dry winters.
The National Weather Service said the storm “looks ESPECIALLY good for September,” which is usually dry. A few hundredths to 0.10 inches of rain are possible across the region (with some isolated spots there will likely be more), which is 50 to 100% of normal September precipitation, the weather service said.
Latest 7-day precipitation forecast tonight through early Thursday, September 23 c / o @NWSWPC. A sustained active pattern in mid to high latitudes brings rain to NorCal, looking particularly good for September. A few hundredths to 0.10 “(locally higher) 50-100% September normal for the Bay Area this weekend. Pic.twitter.com/ZwVe5lwGNC
– NWS Bay Area (@NWSBayArea) September 16, 2021
The early-season system is expected to invade the Pacific Northwest on Friday and reach Northern California from Saturday night through Sunday morning.
“We expect most of the rain to fall in the North Bay in general, as we normally see with these systems that come from the Gulf of Alaska early in the season,” said Drew Peterson, a meteorologist with the Meteorological Service.
The weather service said in its forecast that northwestern Sonoma could see 0.20 “to 0.30” with up to half an inch for some of the rainiest spots.
Napa County is likely to be drier and few showers are expected for San Francisco along the coast towards Santa Cruz. Little or no rainfall is expected for the East Bay and South Bay.
“When you arrive in San Jose, the rain shadows you,” said Peterson, referring to the phenomenon common in the Santa Clara Valley, where the mountains protect the valley areas from rain.
On the overall storm, he added, “It’s pretty good for our first storm.”
The chance of rain is expected to increase rapidly along the Oregon-California border early Saturday and then slowly advance south.
“According to the current forecast, some showers over North Sonoma are possible until Saturday afternoon,” said the weather service in its forecast. “The chances of showers will continue to increase north of San Jose through Saturday night. The chances of showers will continue through Sunday afternoon, and again mainly north of San Jose.”
California is in desperate need of rain as reservoir levels sink to record low and the vegetation on the ground has dried up and 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 flames could benefit from moisture.
The best chance of significant rain is over the Dixie Fire, where weather forecasters project one-half to three-quarters of an inch. Weather service expects a tenth of an inch to a quarter of an inch in the South Lake Tahoe area near the Caldor Fire.
The furthest northwest corner of California is likely to have the most rain this weekend; up to 2 inches is possible in the mountains of Del Norte County. Crescent City is expected to see 1.36 inches, Yreka 0.54 inches and Shasta 0.42 inches, the weather service’s Eureka office said.
