A ‘bombogenesis’ storm is about to hit Northern California. What does that mean?

The winter weather is finally here in time for Thanksgiving, and it’s bringing what meteorologists call a “bombogenesis” with it.

But what is a bombogenesis, you ask?

According to the National Oceanic and Atmospheric Administration, a bombogenesis is when “midlatitude cyclone rapidly intensifies,” meaning there is a rapid drop in pressure that results in a strong storm system.

“In a nutshell, it’s just a rapidly developing storm system,” said Bill Rasch, a meteorolgist for the National Weather Service in Sacramento. “And for a meteorologist to call it that, the strength of it has to decrease in pressure at least 30 millibars in 12 hours.”

“They’re unusual, but they’re not unheard of,” he said.

Also known as a “bomb cyclone,” the storms can develop when cold air collides with warm air, the National Ocean Service said.

The last time Sacramento experienced a bombogenesis was in December 2015, Rasch said.

“We’re really trying to get people to adjust their travel because it’s going to be ugly,” he added.

Northern California storm forecast

Between 8 and 18 inches of snow are forecast to fall above 1,500 feet elevation, meaning foothill communities like Shingle Springs, Placerville, Colfax, Auburn, Grass Valley and Nevada City could all get snow.

Even more snow – between 2 and 3 feet – is expected to fall above 3,000 feet elevation and 4 feet is forecast for the higher peaks. And snow is even forecast for lower elevations between 500 to 800 feet in the Redding area and other parts of the Sacramento Valley.

Communities in the Valley are expected to be pounded with wind and rain. A wind advisory issued early Tuesday warns of “strong southerly winds” that are expected to sweep through the valley Tuesday evening into Wednesday morning as a “powerful winter-like storm moves into the region.”

The wind gusts are expected to reach up to 50 mph and will push sheets of rain into the Valley, Rasch said.

The strongest winds will hit Tuesday evening, the advisory said, and create “difficult driving conditions.”

Travel through impacted areas is “highly discouraged,” the National Weather Service said.

This story was originally published November 26, 2019 at 9:04 AM with the headline "A ‘bombogenesis’ storm is about to hit Northern California. What does that mean?."