‘It’s A Massive One’; Weekend Atmospheric River Gaining Depth Off California Coast – CBS San Francisco
SAN FRANCISCO (CBS SF) – While residents of the San Francisco Bay Area dodged some light raindrops early Wednesday, a much larger atmospheric flow continued to intensify offshore, with the risk of up to 5 inches of rain in the coastal mountains in the coming Time brought the weekend.
The large cloud stretched hundreds of miles across the Pacific and attracted tropical moisture from the Hawaiian Islands – an unusual development for this time of year.
Latest KPIX 5 forecast
When asked about the intensity of the storm, Marty Ralph, director of the Center for Western Weather and Water Extremes in La Jolla, did not mince his words.
“It’s an early start for us – and it’s a big one,” he told the Washington Post.
Atmospheric river forecast – Center for Western Weather and Water Extremes graphic
Weather forecasters said the first blast of moisture brought showers to the Bay Area overnight. According to the National Weather Service, coastal areas in Sonoma and Marin counties received up to an inch of rain, with only about 0.10 inches falling in the lower elevations around the Bay Area.
Another pulse should drop south and inland from Thursday night through Friday morning, bringing with it light to occasional moderate rainfall.
Early Wednesday, the National Weather Service warned of possible flash floods in the areas of the Dixie and North Complex fires on Thursday evening and through Friday morning. Heavy rains are expected to cause ash and other debris flows, and residents should plan for a possible evacuation.
⚠️ For the burn scars of the Dixie Fire and North Complex, a Flash Flood Watch was issued for possible ash or debris flows from late Thursday evening to Friday morning. Heavy rain is to be expected during this time. Be ready to evacuate when prompted by local officials! #cawx pic.twitter.com/Jzh7GcnTvt
– NWS Sacramento (@NWSSacramento) October 20, 2021
The first storm of the week passed on October 17, bringing in enough snow to block highways over the higher passes of the Sierra and require chains for vehicles on Interstate 80. UC Berkeley Central Sierra’s snow lab at Donner Pass reported 10.3 inches of snow Monday at 8 a.m.
“That was a pretty wild ride for the first real storm of the year,” tweeted the California Highway Patrol Truckee office.
But these storm systems are just the prelude to the atmospheric flow that is expected to arrive Sunday evening through Monday.
“(We expect) 3.00” -5.00 “rainfall along the coastal areas with a total of 1.00” -3.00 “elsewhere,” said National Weather. “Strong and gusty winds will likely accompany the slow moving frontal boundary as it moves south through the region.”
The last strong atmospheric river rushed into the Bay Area on January 27th.
The torrential rains caused flooding in the Carmel River area, sparked multiple mudslides in the fear of the Carmel, River and Dolan wildfires, dumped 15 inches of rain over the Big Sur region, and dumped 7 feet of snow in Lake Tahoe.
Sunday’s flood will bring welcome relief to a region that has suffered from extreme drought conditions for months.
On Tuesday, Governor Gavin Newsom issued a proclamation expanding the drought emergency nationwide and further urging Californians to step up their water conservation efforts in light of historic conditions.
Erik Ekdahl, an assistant director of the State Water Resources Control Board, warned of the storm’s impact on Sunday in relation to the drought.
“A storm is great, but we will need a few to get us back into a robust and healthy storage condition,” said Ekdahl.
Unlike a typical calendar year, California’s water year begins on October 1, and the final season the drought-stricken region left was one of the driest on record.
According to the National Weather Service, normal rainfall for Santa Rosa is 36.28 inches from October 1 to September 30. In the last rainy year, the area got only 13.01 inches, or 39% of normal.
For San Francisco these sums were 23.65 inches for a normal year and only 9.04 inches fell in the 2020-2021 water year. It was the second driest in more than 170 years.
San Jose should typically be 14.90 inches with only 5.32 inches dropping during the water year.
