Northern California braces for storm bringing rain, snow, wind and potential ‘bomb cyclone’
Northern California and the Pacific Northwest residents on Tuesday were bracing for the strongest atmospheric river storm system, bringing a lot of rain to some areas and creating the potential for a “bomb cyclone” that can intensify wind overnight.
The storm was expected to move into the region late Tuesday afternoon and linger through Saturday morning, according to the National Weather Service in Sacramento. The atmospheric river system was expected to produce a prolonged period (48 to 72 hours) of rain, mountain snow with rising snow levels and gusty southerly wind.
The weather service forecast updated on Tuesday morning indicated the storm, moving east from the Pacific Ocean, was expected to push onshore Tuesday afternoon into Wednesday morning.
About 3 to 4 inches of rain was expected to fall over the next few days in the Sacramento area, according to the weather service. Areas farther north, such as Chico, Red Bluff and Redding, were expected to receive several inches of rain before the storm pushes out of the region.
Meteorologist will know over the next 24 hours whether the storm system developed what they call a “bombogenesis,” commonly referred to as a “bomb cyclone,” said Scott Rowe with the weather service. The term bomb cyclone refers to when a midlatitude (the latitudes between the tropics and polar regions) cyclone rapidly intensifies or strengthens over a 24 hour period.
Rowe said a bomb cyclone will strengthen wind speed. A bomb cyclone can happen when a cold air mass collides with a warm air mass, such as air over warm ocean waters.
“I don’t believe it’s bombed out yet,” said Rowe, a meteorologist and hydrologist. “We won’t know until after it happens.”
He said a bomb cyclone will intensify wind along the coast, and it can sometimes strengthen wind further onshore and even as far inland as Sacramento.
In early January 2023, an atmospheric river storm and bomb cyclone were part of series of storms that created an onslaught of damage through flooding, power outages, mudslides and fallen trees throughout Northern California.
The weather service has issued a wind advisory for the northern and central Sacramento Valley from 11 p.m. Tuesday through 4 p.m. Wednesday. Forecasters predicted wind gusts of up to 35 to 45 mph at times, which will cause difficult driving conditions, loose objects to be blown around, downed tree branches and the potential for power outages.
Rowe said it’s not unusual to see an atmospheric river storm system move through Northern California in mid-November since it is the beginning of the region’s wet season. But, he said this storm system is considered the strongest of the season, so far, since only 0.9 of an inch of rain has fallen in Sacramento this season. Historically, the wettest part of the season is in December, January and February.
Courtney Carpenter, a weather service warning coordination meteorologist, said in a Tuesday morning briefing on the storm that the heaviest precipitation was expected north of Interstate 80. She said widespread flooding was not expected given the dry soil throughout the region.
Forecasters expected the storm will produce enough rain to create sharp rises in creeks, streams and rivers, along with creating problems for commuters. Additional lighter rain and mountain snow was expected on Sunday and into Monday, according to the weather service.
A winter storm advisory will go into effect at 4 p.m. Tuesday and continue through 10 p.m. Wednesday for the higher elevations in Northern California. Forecasters expected to see heavy snow and gusty wind up to 50 mph during this time, and drivers should be prepared for slick and snow-covered roads.
The weather service predicted the storm will drop 10 to 20 inches of snow above 4,500 feet in the Sierra Nevada mountains and the coastal range, along with 5 to 10 inches of snow in the elevations down to 3,500 feet. About 5 to 10 inches of snow was expected to fall in the elevations above 3,000 feet in Shasta County.
Drivers in the Sacramento Valley, from Tuesday evening through Saturday morning, should expect moderate rainfall with slick roads and ponding water on roads, creating longer commutes, according to the weather service.
A flood watch, issued by the weather service, remains in effect from 10 p.m. Tuesday through 4 a.m. Saturday for the northern and central Sacramento Valley and the adjacent foothills below 3,000 feet.
This story was originally published November 19, 2024 at 12:51 PM.
