Fires have surrounded the Bay Area for weeks, but they started having a new impact on the region today.
The dark, oddly colored sky that many awoke to find Wednesday morning strongly signaled that there had been abrupt change to the weather.
Meteorologists have been warning of a significant offshore wind that could dramatically affect existing fires.
That forecast became reality, putting fire crews to the test starting Tuesday.
Crews battling the Bear Fire, which is now threatening Oroville, encountered extreme fire behavior. At one point, the fire was spreading at a rate of 1000 acres per minute.
Why is it so dark and smoky in the Bay Area?
A northerly, upper-level wind transported the smoke from the fires overnight. Unprecedented fire behavior on Tuesday sent a tremendous amount of smoke tens of thousands of feet into the sky. Previous fire events have produced a thin layer of smoke.
Right now, we are experiencing a smoke plume that is extremely thick, essentially blocking our daylight. Since the upper level winds have been the main transport mechanism, most of the smoke we are seeing is aloft, and not having as much of an impac at the surface.
According to the Bay Area Air Quality Management District, smoke particles scatter blue light. This sets up the strange yellow/orange/red sky we are experiencing today.
What could happen next?
The upper level winds from the north will weaken. This may allow the suspended smoke particles to fall closer to the earth, impacting our air quality later tonight.