Weird winter weather hits SF Bay Area with 80-degree temps, offshore winds – SF Gate

Weather that's more typical of late summer to fall in the San Francisco Bay Area is coming Tuesday.

Temperatures are expected to soar to unseasonable highs, with some spots in the North Bay likely to break 80, and desiccating offshore winds are forecast to kick up.

This morning, offshore winds, also known as Diablo winds, were already blowing at 25 mph to 35 mph in the North Bay mountains and East Bay hills reaching 40 mph. They are forecast to increase through the day and peak Wednesday with gusts at the highest peaks reaching 40 mph to 50 mph.

In the East Bay, winds could howl down into the valley, with sustained winds of 10 mph to 20 mph and isolated gusts up to 30 mph.

The National Weather Service has a wind advisory in effect 10 a.m. to 10 p.m. Wednesday for the North Bay Mountains, East Bay hills and valleys and the Santa Cruz Mountains.

Gusty winds could knock down trees, lead to power outages and blow around unsecured outdoor objects, the weather service warned.

The highest temperatures of the week is expected to hit Tuesday with the Santa Rosa Airport projected to reach 79 degrees, Concord 76 and downtown San Francisco 71.

"Eighties are definitely possible," said Matt Mehle, a forecaster with the weather service. "The North Bay valleys will be anywhere from 15 to 20 degrees above normal. San Francisco will be up to 10 degrees above normal."

The warm temperatures and offshore winds are a more typical weather pattern in the fall when the wildfire danger is high. With recent rains, the fire danger will be less in this February event.

The weather conditions are the result of a storm known as an inside slider that was straddling Northern California, southern Oregon and northeast Nevada on Tuesday morning. The system is forecast to drop down into the Great Basin into Wednesday, kicking up offshore winds in Northern California. These easterly winds blow from inland valleys toward the coast, carrying warm air and pushing up temperatures.

"Earlier in the year, we had a tremendous offshore flow event," said Mehle, referring to the mid-January wind storm when gusts up to 90 mph belted the region. "Its not unheard of in winter but its more common in late summer to fall."

Temperatures are expected to drop 10 degrees from Tuesday to Wednesday and afternoon highs across the region tomorrow should range from the mid-60s to 70s.

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Weird winter weather hits SF Bay Area with 80-degree temps, offshore winds - SF Gate