October 27, 2019

An Extreme Wildfire Danger Will Develop In Northern California On Sunday

Dangerous fire weather conditions will develop across much of northern California on Sunday. A period of powerful winds and bone-dry humidity could allow even a tiny spark to grow into an out-of-control fire in short order. Authorities have issued a mandatory evacuation order across a significant portion of Sonoma County as worsening weather conditions could allow the Kincade Fire to rapidly grow and spread toward the Pacific Ocean.

The Storm Prediction Center's fire weather forecast for Sunday highlights an area of extremely critical fire weather conditions north of the Bay Area—including Santa Rosa, Napa, and Davis—with critical fire weather conditions existing along a swath from Fresno County to Shasta County. The agency used the term "potentially historic" to describe the fire weather threat in this area on Sunday, language they don't use lightly.

Forecasters also expect critical fire weather conditions to develop in southern California along the Transverse Ranges near Los Angeles.

High winds are likely across California on Sunday as a tight pressure gradient develops over the state. The strongest winds are likely in northern California, where we could see a widespread area of sustained winds of 40+ MPH with gusts reaching 60 MPH or higher beginning Sunday morning and lasting through the evening hours.

Winds descending on the leeward side of the mountains will warm and dry as they reach lower elevations, leading to the warm temperatures and extremely low humidity that will contribute to favorable conditions for rapid fire growth on Sunday.

Sonoma County's evacuation map around 11:00 PM PT on October 26, 2019. Areas in purple are under a mandatory evacuation. Areas in blue are under a voluntary evacuation. The area in red is the extent of the Kincade Fire.

This is a dangerous situation. Authorities have issued mandatory evacuation orders to everyone near and downwind of the Kincade Fire, stretching all the way to the coast. The situation on the ground in the evacuation area is otherworldly, with air raid sirens blaring across a moonlit horizon darkened by PG&E's blackout.

More than a million people are without power tonight as part of PG&E's Public Safety Power Shutoff program, and more power outages are likely as the winds pick up on Sunday. The goal of the intentional blackouts is to prevent downed lines or equipment failures from igniting fires on windy days; however, this may not have been enough to prevent the Kincade Fire, which reportedly started near a set of powered transmission lines during Wednesday night's blackout.

Weather conditions in northern California should become less favorable for major fire development by Monday morning as winds begin to die down.

[Top Image: Smoke from the Kincade Fire on October 24, 2019 via NOAA]

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I graduated from the University of South Alabama in 2014 with a degree in political science and a minor in meteorology. I contribute to The Weather Network as a digital writer, and I've written for Forbes, the Washington Post's Capital Weather Gang, Popular Science, Mental Floss, and Gawker's The Vane. My latest book, The Skies Above, is now available. My first book, The Extreme Weather Survival Manual, arrived in October 2015.