First rain in a month is forecast for weekend

It won’t solve California’s drought problems, but it’s better than nothing.

The first rain in a month could wet the Bay Area and much of Northern California this weekend, forecasters say, as a late-season storm from the Gulf of Alaska appears to be headed toward the region.

Computer models show the rain will begin late Saturday in the North Bay, spreading across the wider Bay Area and Santa Cruz Mountains on Sunday.

Forecasters said the system — which would be the first sig

nificant rain since March 18 in the Bay Area — appears to be on track to deliver about .25 of an inch along the coast and to Bay Area cities, with about half an inch in the Santa Cruz Mountains and up to 1 inch in the North Bay Hills.

“We’re happy to see it,” said Brayden Murdock, a meteorologist with the National Weather Service in Monterey. “Things have been very dry. It’s nice to see a wet pattern come through.”

Although it might seem like it rarely rains in April, actually April is the sixth wettest month of the year in the Bay Area, averaging 1.46 inches in San Francisco. That ranks April behind December, January, February, March and November, according to rainfall records. But it still leaves April with double the average monthly rainfall of May, more than October and considerably more than the driest months, September, June, August and July.

In fact, you have to go back to 1949 to find an April where San Francisco, as a proxy for the wider Bay Area, did not receive any measurable rain, said Jan Null, a meteorologist with Golden Gate Weather Services in Half Moon Bay.

Having no rain in April this year might seem normal, however, because the entire winter rainy season was so dry this year and last year.

“The rainfall amounts this weekend will be negligible in terms of water supply,” Null said. “A lot of it is going to soak in. But every bit of moisture puts off fire danger by a few more days, which is the biggest impact.”

The weekend system also could bring snow to the Sierra Nevada on Sunday.

“Sierra passes could experience periods of heavy, wet snows Saturday night into Sunday and Monday with possible travel impacts and chain controls, especially at night,” the National Weather Service’s Sacramento office said in a forecast updated Tuesday. The rain won’t last long. “It’s going to be another fast-moving system,” Null said. “In before noon Sunday and out by dawn on Monday.”

The late-season cloudburst comes as much of California is heading into a drought following two dry winters in a row.

Through Monday night, San Francisco had received just 8.72 inches of rain since Oct. 1 — 39% of its historical average for that time period. Oakland has had 7.57 inches, also 39% of normal. And San Jose has received 5.27 inches, or 38% of normal.

The Sierra Nevada snowpack, the source of about one-third of California’s water supply, is in a similar deficit, at 39% of normal.

Murdock noted that the rain won’t even come close to busting the drought. But it will help clear dust and soot pollen from the air. It will reduce fire danger, at least temporarily. And it will give Northern Californians another reason to turn off their sprinklers to help conserve water.