SAN FRANCISCO – A major atmospheric storm is heading towards northern California, promising to drop up to 10 feet of snow on the Sierra Nevada mountain peaks and much-needed rains throughout the region.
Rains were expected this weekend in the bay area, with snowfall in the Sierras from Sunday before intensifying between Monday and Tuesday, forecasters said. There might even be a blanket of snow on the mountain peaks in the Bay Area.
“If you live in the Sierra, today is the last day to prepare for a multi-day winter storm that will likely be remembered for years to come,” the National Weather Service warned in a forecast released Saturday.
Mammoth Mountain Ski Resort issued a “fresh snow alert” Friday morning celebrating about 10 inches of new powder, while UC Berkeley Central Sierra Snow Lab reported more than 5 inches in the Tahoe area. .
Southern skiers were also cheering as about 3 inches of snow had accumulated around Big Bear.
Another storm system expected to hit California mid-week could provide nearly continuous snowfall, said Scott McGuire, a meteorologist in the Weather Service’s Reno office, which monitors an area straddling the Nevada state border.
“If you are traveling through the Sierra, get ahead of the storm before the snowfall starts or wait until the end to get there. It will be more and more treacherous, ”he said.
A low pressure from the Pacific Northwest was on course to hit coastal areas north of San Francisco on Saturday night and drop light rains. The heaviest precipitation is expected to fall from Sunday evening through Monday morning as the storm spreads east and south, said Sarah McCorkle, a meteorologist in the Bay Area Weather Service office.
Extended warnings until Tuesday:The storm will bring snow, rain
Precipitation totals in the north could vary between 2 and 6 inches, and the greatest amount was expected in the Santa Cruz and Santa Lucia mountain ranges, where winds could exceed 50 miles per hour. The rain could cause minor flooding and landslides, especially in areas where forest fires have recently burned down, according to forecasts.
Pacific Gas & Electric said the storm could cause power outages in the Bay Area. The utility said in a press release that its workers cleared vegetation from power lines to reduce the risk of blackouts.
The amount of rain is typical for this time of year, McCorkle said, although the past two years have been unusually dry. The storm is expected to help ease the dry conditions, but will not mark the end of the drought, according to the US Drought Monitor.
The mega-drought fueled by climate change has affected much of the West. As California heads for what is traditionally its wettest time of the year, 80% of the state is classified as extreme or exceptional drought, the two worst categories.
The latest storm follows a powerful “bomb cyclone” that dropped several inches of water in the state’s north and south.
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The winter storm is listed as a “strong” Category “AR 3” system by scientists studying the powerful storms that feed California with most of its water.
In 2019, scientists studying storms known as “atmospheric rivers” agreed on a rating scale similar to the “Cat” system used to describe a hurricane.
An “AR 1” is the weakest system. An “AR 5” is the most destructive. The five categories on the Center for Western Weather and Water Extremes at Scripps Oceanography list are “weak”, “moderate”, “strong”, “extreme” and “exceptional”.
A notorious example of an AR 5 was the New Years Day flooding of 1997, which killed at least nine people and inundated 300 square miles of California.
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The incoming “strong” AR 3 may be in the middle of the scale, but it will still bring impressive amounts of precipitation when it hits.
Atmospheric rivers form over the Pacific Ocean when strong winds drive a fire hose of tropical moisture to the ocean surface.
The 500 mile wide water conveyor belts can last for days and can hit California wave after wave. They provide up to half of the state’s rainfall and snowfall each year. Bigger storms can produce as much rain as a major hurricane.
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Notably difficult to predict, the US Air Force Reserve regularly sends its “Hurricane Hunter” aircraft over the Pacific to perform scientific measurements on atmospheric rivers in the hope of better understanding storms for more accurate long-term forecasts. .
The effects of next week’s storm will likely include travel delays, potential for debris flow in recent burn areas, localized flooding, mud and rock slides on mountain roads, and driving conditions. dangerous winter in the mountains at about 5,000 feet, the weather service said.
A severe frost warning will be in effect in the Antelope Valley Friday evening, and frost and freeze advisories are in effect for parts of San Luis Obispo, Santa Barbara and Los Angeles counties through Saturday.
The Sacramento Bee and the Los Angeles Times contributed to this report.