Rain may grace Bay Area, but not enough to stem drought

The Bay Area might see enough rain this weekend to hit 100% of the normal amount for September, according to the National Weather Service — but that still isn’t much, experts cautioned, and it’s far from “drought-busting.”

The agency is predicting that the Bay Area could see a few hundredths to 0.10 inches of rain — which would bring the region to 50-100% of the normal amount of precipitation for the month. However, September in the Bay Area usually doesn’t see a lot of rain, so even “one little shower” can bring the full month’s worth of rain, officials said.

The rain is most likely to fall between Saturday afternoon and Sunday morning, weather service meteorologist Gerry Diaz said. That rain will likely begin over the “far north” portions of the Bay Area, including northern Napa and Sonoma counties, he said.

Rain in the North Bay could move southward — it just depends on how much rain actually develops, Diaz explained.

This weekend will see “slightly above average”

This weekend will see “slightly above average” levels of “precipitable water,” or moisture in the air that can become rain, Diaz explained. But that doesn’t necessarily mean rain will actually fall — things like mountain ranges or cold fronts lift that moisture, helping it “manifest” as rain. It’s hard to predict how much that will happen, he said.

Still, even if the rain is light, the moisture does temporarily alleviate fire weather worries for the North and East Bay areas, Diaz said. While there is a chance the first offshore “Diablo” winds of the season could arrive this weekend — which can help spread wildfires when they do develop — the moisture keeps those fire concerns at bay.

The “modest moisture” — without the accompanying threat of lightning — likely also will reduce activity from the big fires burning in Northern California, UCLA climate scientist Daniel Swain wrote on his weather blog. But unlike in the Pacific Northwest, where “fire season ending” precipitation is expected this weekend, predicted rainfall of 0.1-0.3 inches in Northern California will reduce fire risk for only a few days except along the North Coast, Swain said.

Diaz said in areas that haven’t seen rain in a while, it’s important to drive carefully, since more oil latches onto the roads this late into the season after months of no rain.

“Be sure to be extra cautious when you’re on the road,” he said.