Offshore winds are rolling into California today. Here’s how they affect the Bay Area

It’s a cold morning in the Bay Area, but temperatures will change a bit today. Warm, dry air enters the Napa Mountains and Diablo Range. This air accelerates as it enters San Francisco Bay, clearing any remaining clouds and fog in its paths.

It was only a matter of time before those dry, offshore, and northeasterly winds—also known as Diablo winds—appeared. Southern California will also see the return of the Santa Ana winds, while the Santa Barbara coast can expect sundowners along the Pacific Coast Highway.

With all the rain and snow we’ve seen over the past few weeks, how concerned should Californians be about new wildfires during this week’s wind event? Depending on what part of the state you live in, the answer will vary quite a bit.

The offshore winds are back

As a quick refresher on offshore winds, you need two ingredients for Diablo, Sundowner, and Santa Ana winds to develop. The first is a depression sliding into California. And that’s exactly what global weather models like the European and Canadian forecast for Tuesday and Wednesday. The catch is that the system must be dry enough for Diabos to bear fruit, for its winds to dry California like a blow dryer on wet hair.

That leads us to the second ingredient: time. Anyone who has dealt with frizzy hair knows that the longer you can dry your hair, the greater the chances for smoother results. When it comes to offshore winds, the longer they hit California, the drier the state’s soils become.

Tuesday afternoon's peak wind gusts are from the weak Diablo winds over the Bay Area.  Gusts of up to 40 miles per hour are possible on the highest peaks of the Vaca Mountains and the Napa Highlands.  More widespread gusts up to 30 mph are likely in the remaining counties of Napa, Solano, Contra Costa and Alameda.  Breezes, but wetter winds also form offshore in San Mateo County along Highway 1 and in places in the Santa Cruz Mountains.

Tuesday afternoon’s peak wind gusts are from the weak Diablo winds over the Bay Area. Gusts of up to 40 miles per hour are possible on the highest peaks of the Vaca Mountains and the Napa Highlands. More widespread gusts up to 30 mph are likely in the remaining counties of Napa, Solano, Contra Costa and Alameda. Breezes, but wetter winds also form offshore in San Mateo County along Highway 1 and in places in the Santa Cruz Mountains.

Gerry Diaz / Weather Bell

Based on the latest multi-model analysis of the European, Canadian and American weather models, these offshore winds are likely to start Tuesday and continue through Wednesday. In the Bay Area, this means that Napa, Solano, Contra Costa, and Alameda counties can expect outbreaks of Diablo winds during those two days. Luckily, the strongest of these winds are concentrated at higher altitudes and just barely meet the Diablo wind criteria.

It’s the equivalent of trying to dry your hair with a blow dryer on the lowest setting in under a minute. Sure, you’ll see a few patchy areas dry up, but most of it stays frizzy. In the case of California, our recent rain and snow events have left most of the state’s soil saturated. This means it takes a lot more than weak bursts of Diablo winds to raise fire concerns.

Unfortunately for Southern California, strong offshore winds — also known as the Santa Ana winds — will sweep into the region. Red flag warnings are in effect for the Santa Monica Mountains and Ventura County Mountains in Los Angeles, and high wind warnings are in place for the San Bernardino, San Gabriel and San Jacinto Mountains from 7 a.m. Tuesday through 7 p.m. Wednesday.

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