The overcast above the Bay Area grew a little darker Wednesday. The smoke dropped a little bit lower.
The events were as expected, weather and air quality officials said, and they insisted the two did not mean the air was as unhealthy to breathe as it appeared to be.
“It was all brought up by those northerly winds that we were anticipating bringing the smoke down” from wildfires in Northern California, National Weather Service meteorologist David King said. “So yeah, it was anticipated to be a bit smokier. Luckily, getting into (Thursday), we’ll see more of an on-shore push and that will push things even more inland.”
The northerly winds were produced by a low-pressure trough that has migrated through the region, bringing down sizzling triple-digit temperatures into the 90s in much of far inland regions. By 1 p.m., it had moved far enough east and taken the winds with it that the National Weather Service had cancelled a red flag warning for the East Bay hills and North Bay.
The same warning remained in effect in the Sacramento Valley and in areas around Redding and Eureka and is scheduled to stay that way until 8 p.m. Thursday according to the weather service.
The system also weakened just a bit the marine layer that has kept the smoke from the Dixie, River and Caldor fires at a ceiling of about 8,000 feet. On Wednesday, the weather service said the smoke was between 3,000 and 5,000 feet above the surface.
“The way the weather pattern sets up, the smoke is having more time to sink,” King said.
That said, it won’t sink low enough to create unhealthy breathing conditions in the Bay Area, according to air quality forecasts. The Bay Area Air Quality Management District issued an air advisory but not a Spare the Air alert.
AirNow, a real-time air quality measuring service that the weather service uses, recorded figures at 1 p.m. throughout the region that showed the fine particulate matter between 51-100, air considered moderately healthy to breath, nearly everywhere. One exception was Livermore, where the reading was 106, meaning the air is unhealthy for those with breathing problems.
The smoke was worse in Sacramento, where patches of smoke got so low as to record an air quality figure of 177. Anything between 151-200, which is considered unhealthy for all people.
In South Lake Tahoe, the air quality rating at 1 p.m. was 151.
King said that as the trough continues to move, the marine layer will gain back some of its thickness and that the haze may begin to fade as the weekend approaches.