Atmospheric river carrying 'wall of rain' arrives late Monday night

SAN FRANCISCO -- While much of nation was battling snow and bitter cold temperatures Sunday, Mother Nature delivered a holiday gift of an unseasonably warm weather to the Bay Area.

But it will only be a brief respite.

Brewing out in the Pacific was a powerful winter storm that will arrive in the North Bay on late Monday night. The winds of the jet stream were mixing the unsettled air from the Northern Pacific with a plume of moist, tropical moisture from near Hawaii.

Once called a 'Pineapple Express', the potent storm is now ranked by the researchers at Scripps Center for Western Weather and Water Extremes as a Cat. 4 atmospheric river on scale that tops out a 5.

"This is a fairly strong one," said KPIX meteorologist Darren Peck of the Monday/Tuesday atmospheric river. "So it's going to give this storm a lot of extra rain to work with. That's a wall of rain by the time we get to Monday night."

Precipitation will begin in the North Bay on Monday, becoming moderate to heavy late Monday night, then spreading south across the region during the day on Tuesday.

How much rain are we talking about?

"Rainfall totals will range from 1 to 3 inches, with higher elevations receiving upward of 3 to 5 inches," the National Weather Service predicted. "Locally up to 7 inches are possible over favored peaks and higher terrain of the Sonoma Coastal Range where prolonged moderate to heavy precipitation and higher rain rates are currently forecast."

The steady downpours will impact roadways and hillsides.

"Moderate to heavy rain will lead to rapid rises of area rivers, streams, and creeks," the weather service said. "This system will result in an increased risk of mudslides and debris flow over wildfire burn areas Localized ponding of water in low-lying or poorly drained areas as well as localized flooding is possible due to blocke culverts, drainages, and storm drains."

The weather service predicted that Monday-Tuesday will be the start of a wet week.

"Like the Jelly of the Month Club, a stout jet across the entirety of the Pacific Basin will be the gift that keeps on giving as it delivers additional waves of moisture across the West Coast," forecasters at the weather service's Reno office predicted. "Potentially up to three additional waves of moisture will be possible before the New Year with systems possible again on Thursday, Friday, and  Saturday and additional waves arriving through the first week  of January."

"Timing of these upcoming storms are still to be determined, although it's becoming likely that they will be cooler and wetter than our upcoming storm on Tuesday."