Two rain systems headed for Bay Area with up to 9 inches expected Monday

The National Weather Service is forecasting more rain to arrive in the Bay Area late Thursday and into Friday, but the biggest rainfall amounts are expected on Sunday into Monday via an “atmospheric river” that could bring up to 9 inches of rain to some elevated parts of the region.

Forecasters said the rain coming through Thursday night into Friday afternoon will affect the North Bay more than other parts of the Bay Area, with areas south of the Golden Gate not expected to get more than a half-inch of rain from the storm.

Southerly winds of 30-40 mph with gusts up to 50 mph along the coast and higher elevations could blow through the region, according to the weather service.

However, the most serious storm will come this weekend, with the atmospheric river possibly bringing 6 to 9 inches of rain in areas like the North Bay mountains and up to 3 inches in other parts of the region.

Flooding is possible as a result of the weekend storm in areas with poor drainage, but forecasters said the weather system is still too far away to make more exact predictions.

The major weather system this weekend will also bring major waves along the coast, with swells as high as 20 to 30 feet coming starting Sunday and peaking Monday into Tuesday, according to the weather service. The same weather system is expected to to dump up to 18 inches of snow in the Sierra Nevada.

As a result, agency officials said a high surf advisory or warning could be issued as soon as Friday, and people are advised to keep an eye out for rip tides and sneaker waves as well as hazardous conditions for small vessels on the water.