A powerful storm system is set to approach the West Coast of the USA this weekend, soon after the 'bomb cyclone' pushes east of the Rockies. The storm will bring more rounds of heavy rain and snow to California, beginning on November 30 and December 1, 2019.
According to AccuWeather, about 76 to 152 mm (3 to 6 inches) of rain can fall over the lower elevations of Northern California, and a maximum of 254 mm (10 inches) can fall on the southwest-facing slopes of the Coast Ranges and hills of the Sierra Nevada.
From the cold to windy and soggy this weekend, begins Sat PM. Atmospheric river connection is there, expect localized runoff and flooding issues esp near the mtns and heavy Sierra snow #CAwx pic.twitter.com/wlt5s6UyrV— Rob Mayeda (@RobMayeda) November 28, 2019
Here’s a morning update regarding precipitable water values for the next storm system poised to generally impact the entire state, but this time with the added possibility of hydrological impacts for the central & northern half of California. #CAwx #AtmosphericRiver #CAwater pic.twitter.com/tRj4yno9fQ— 805 Weather (@805Weather) November 28, 2019
Over in the high country, AccuWeather added that 0.9 to 2 m (3 to 6 feet) of snow can fall across the four-day period, from Sunday to Wednesday, December 4.
"It is possible that Southern California catches an episode or two of heavy rain and mountain snow as well," said AccuWeather senior meteorologist Brett Anderson. "Right now, the best chance of heavy precipitation for the Los Angeles and San Diego areas would be toward the middle of next week."
The atmospheric river is likely to hit the Bay Area. "The weekend is going to be quite interesting," said Brian Garcia, a meteorologist with the National Weather Service. "The storm door is definitely open. We’ll continue to see showers and really cold temperatures especially into later parts of this week."
#BombCyclone to now #AtmosphericRiver potential over SF #BayArea Saturday into Tuesday. Watch the green to blue color surge, that's moisture 140 to 200% of normal. Rain may exceed 1.00 - 2.00" over 4 days. Travel delays ahead! More @nbcbayarea 5, 6 & 11 pic.twitter.com/bdYMV4Qme6— Jeff Ranieri (@JeffRanieri) November 27, 2019
However, Garcia added that the air mass will start to feel warmer and the "pattern is setting up" for an atmospheric river to head over the Bay Area overnight Saturday and into Sunday.
Atmospheric rivers are "supercharged" storm systems that can bring huge amounts of snow and rainfall in just a span of few days.
Garcia said the atmospheric river is expected to arrive somewhere along the coast over the weekend but the exact landfall would be complex to forecast for now.
Predicting accurately where it lands would be challenging in advance since it's a narrow band of heavy precipitation, he added.
"It being narrow and the state being so big, 16 to 24 km (10 to 15 miles) north or south can make a world of difference," said Garcia.
An Atmospheric River (AR) runs through it (Central Coast). They are informally called the “Pineapple Express”; many meteorologists simply referred to these events as “the hose.” Whatever you call it, an AR may take aim at Monterey, SLO and Santa Barbara counties this weekend. pic.twitter.com/cxCtYPR3uF— John Lindsey (@PGE_John) November 28, 2019
Forecasting models show the atmospheric mostly impacting the far southern Bay Area into the Central Coast. However, even a small change of path between November 29 and Saturday night could bring the center nearer the densely populated parts of the Bay Area, or bring piles of snow to the Sierra-- all this event on one of the busiest travel days of this year.
"This could have some pretty significant impacts throughout the center portion of the state," said Garcia. The forecast calls for storms to continue slamming the Bay Area over the next 5 to 10 days.
"In a sense, fire season has come to an end, and mudslide and flash flood season is beginning in California," warned Dale Mohler, AccuWeather Senior Meteorologist.
The stormy pattern is not likely to end after mid next week. Storms are piling up across the North Pacific, and at least some of these weather systems will approach Northern California during the first half of December.
California will bear the brunt of at least 2 "atmospheric river" systems over the next 5-8 days.— Ryan Maue (@RyanMaue) November 27, 2019
Winter storms in the Gulf of Alaska have conveyor belts of moisture extending out of the subtropics.
These narrow "rivers" of moisture are directed into the West Coast. pic.twitter.com/fKzGFYihhI
Traffic is at a standstill on I-80 in California over Donner Summit amid snowy conditions.— AccuWeather (@breakingweather) November 28, 2019
Similar scenes may unfold through next week as an atmospheric river flows into California: https://t.co/Bmxp1DByHt pic.twitter.com/9qnp7UQGeU
Featured image credit: windy.com Acquired Dec.1, 2019.