Smoke anticipated to return to the San Francisco Bay Space. Get the forecast.
Smoke from wildfires burning in California’s northwest corner is forecast to push into the San Francisco Bay Area on Thursday and Friday, before clearing over the weekend, the National Weather Service said.
The sooty air will be mostly aloft higher in the atmosphere, and while skies may be hazy, air quality levels are not expected to reach unhealthy levels and exceed federal health standards for prolonged periods of time.
Smoke may mix down to the surface at times through the day, causing isolated pockets of elevated pollution levels, the Bay Area Air Quality Management District said.
The district has an air quality advisory in effect Thursday and Friday. An air quality advisory is less severe than a spare the air alert, which signals unhealthy air quality levels and bans wood burning.
Air quality conditions are expected to range from “good” to “moderate” on the Air Quality Index, which operates on a scale from 0 to 500. “Moderate” air quality falls between 51 and 100, while “unhealthy for sensitive groups” is in the 101 to 150 range, and “unhealthy” 151 to 200.
A shift in the winds overnight and into Thursday morning will cause the smoke from fires, such as the Monument Fire in Trinity County, to drift south.
“We have an upper-level trough moving inland overnight,” said David King, a forecaster with the weather service. “We have mostly southwest winds, but as that trough passes, winds will shift to northwest. It’s going to bring a good swath of smoke further south.”
The highest concentrations are expected in the North Bay, King said.
As the trough of low pressure moves inland, high pressure will build over the weekend, triggering the return of the southwest winds that will push the smoke out of the region.
“It will be a gradual clearing, so there might be some lingering smoke on Saturday,” King said. “It’s all going to depend on how much the high pressure is growing and when those winds switch to southwest.”
This forecast could also change as wildfire smoke movement is tricky to forecast and the slightest wind can move a mass of sooty air from one place to another in minutes.
