'Pineapple Express' among atmospheric river events heading towards California

Yahoo

30-01-2025

SAN FRANCISCO – A series of atmospheric river events promise to deliver heavy precipitation across Northern California and the Pacific Northwest in the form of valley rain and mountain snow with the potential for significant impacts around the San Francisco Bay Area.
According to the FOX Forecast Center, the first round of significant precipitation will begin on Friday, with additional waves of moisture through the weekend and into the upcoming workweek.
Forecast models show more than 6 inches of rainfall could occur in the highest rainfall accumulation zones, while feet of snow look likely from the extreme northern Sierra Nevada into the Cascades.
Forecasters say because the air mass originates near Hawaii, which is commonly referred to as a "Pineapple Express," the overall event will be warmer, causing snowfall levels to rise to several thousand feet.
What Is A Pineapple Express?
Due to the cold weather threat, various winter weather alerts have been issued across the Rockies and the Cascades, with counties in Northern California put under Flash Flood Watches.
"Obviously, when you go up an elevation, you can squeeze out a little bit more of that rainfall," said FOX Weather meteorologist Haley Meier. "Overall, snow for portions of Northern California is going to be somewhat limited. But as you get farther north into the Cascades and the coastal ranges, that's where we could see significant snowfall amounts with this system."
Forecast models show much of the moisture will train over the Bay Area and points northward, producing widespread amounts of at least 6 inches of precipitation.
The National Weather Service's Weather Prediction Center has highlighted the area with a slight flash flooding risk, which could be enhanced in the coming days.
Some river levels across the region are already elevated, leading to a greater risk that waterways could overrun their banks.
Every year, dozens of atmospheric rivers impact America's West Coast, unleashing heavy rain, rough surf, mudslides and heavy snowfall.
A wet end to 2024 has led to the region from Northern California to southern Oregon being susceptible to events such as mudslides and low-lying flooding.
Firefighters Watching For Hotspots From California's Deadly Wildfires
While Northern California basks in heavy rainfall, residents in the southern part of the state will be hoping for some added moisture.
Since early January, parts of Los Angeles and San Diego counties have experienced large fires that have destroyed more than 16,000 structures and caused hundreds of thousands of people to temporarily leave their homes.
Nearly 54% of the state is officially in drought conditions, with extreme levels reported in some of the same fire zones.
Since the storm track is not expected to be directly over Southern California, more modest chances of precipitation are expected over cities and communities such as Los Angeles and San Diego, with as much as three-quarters of an inch of rainfall over the next week.
Potentially equally beneficial will be the higher humidity values, which are sure to help tamp down any major flare-ups along wildfires.
"Even if a spot like Los Angeles doesn't see any kind of substantial rain, a little bit of moisture is exactly what you need," said Meier.Original article source: 'Pineapple Express' among atmospheric river events heading towards California