Fire danger in Bay Area rises as offshore winds bring heat and increased fire danger

The upper atmosphere storm system responsible for gusty winds in the Bay Area has moved inland over the Rocky Mountains, resulting in warmer temperatures and significantly weaker winds across most of the region on Thursday.

On the backside of the storm, sustained winds of 10 to 15 mph with stronger gusts from the north-northwest will move through the Sacramento Valley and the hills of the North and East Bays, drying out the air mass during the afternoon.

This combination of offshore winds and decreasing relative humidity will result in a slightly increased fire danger in the hills north of the Sonoma and Napa valleys, as well as in the inland hills of the East Bay and east of Mount Diablo.

The offshore wind direction inland also increases the likelihood that smoke from several fires in Oregon will move into the region later this afternoon and evening.

Due to the inland current, temperatures in San Francisco and on the coast will be between 15 and 21 degrees Celsius, but away from the water temperatures will rise to 27 to 32 degrees Celsius, noticeably warmer than yesterday.

This warming trend inland will continue at least until Friday, before a significant cooling occurs over the weekend and temperatures fall by a good 10 to 15 degrees by Sunday.

San Francisco: In the morning, low clouds will move over the city, becoming partly sunny in the late morning and early afternoon. The wind will be from the west and will reach 10 to 20 mph, with stronger gusts in some areas. Highs will be around 65 degrees Fahrenheit in the Sunset and Mission districts, and highs will reach 68 to 70 degrees Fahrenheit in the downtown area. In the evening and at night, clouds will return to most parts of the city, winds will ease, and temperatures will be between 50 and 54 degrees Fahrenheit.

North Bay: In the early morning, clouds will move from the coast to the Petaluma Valley, but will clear quickly. Mostly sunny and warm, with highs between 27 and 30 degrees in Napa, Petaluma, Novato and Santa Rosa. Winds will be from the north-northwest at 10 to 15 mph, with stronger gusts in the higher elevations around Napa and Sonoma. Overnight, partly cloudy with less wind and temperatures around 10 degrees.

East Bay: Low clouds along and west of the Berkeley Hills will clear by mid-morning, leaving a mostly sunny day across the region. Highs will be 70 degrees Fahrenheit in Richmond, Oakland, Hayward and Fremont, with light westerly winds 5-15 mph. Inland, temperatures will be much warmer, with highs between 80 and 85 degrees Fahrenheit in Concord, Dublin and Tracy. Over the inland hills around Mount Diablo, winds will be north-northeast at 10-15 mph with stronger gusts. Air quality may deteriorate somewhat around Concord and inland in places like Brentwood due to wildfire smoke blowing in from the Pacific Northwest. Mostly clear overnight, with lows in the low 50s.

Pacific coast and peninsula: It will start off windy and cloudy along the Pacific coast, with partly clearing in the afternoon. Highs will be between 65 and 72 degrees Fahrenheit in Pacifica, Half Moon Bay and Daly City, with westerly winds 10 to 20 mph. The rest of the peninsula will turn sunny more quickly, with highs between 70 and 77 degrees Fahrenheit in South San Francisco and SFO, and highs around 80 degrees Fahrenheit in Redwood City. Westerly winds 10 to 20 mph. Partly cloudy overnight with lighter winds and lows around 50 degrees Fahrenheit.

South Bay and Santa Cruz: It will be sunny over the South Bay early in the morning, with temperatures rising to 80 to 85 degrees in Palo Alto, San Jose and Gilroy. A brisk north-northwest wind will blow at 5 to 15 mph. It will also be mostly sunny throughout Santa Cruz, with highs around 77 degrees in Santa Cruz and highs around 80 degrees in the mountains. Mostly clear overnight with lows around 50 to 60 degrees.

Reach Greg Porter: [email protected]