Atmospheric river slams California with record rain, prolific mountain snow - The Washington Post

Flood advisories blanketed the Bay Area connected Saturday, with dense rains forcing the closure of Highway 101 successful southbound San Francisco for astir 8 hours. For a time, the road was submerged.

Downtown San Francisco registered 5.46 inches of rain, marking its second-wettest time successful records dating to 1849. December is the city’s wettest month, with an mean of 4.76 inches of rain. But the New Year’s Eve deluge boosted December 2022’s full to much than doubly that: 11.7 inches. Nine Bay Area upwind stations recorded astatine slightest 25 percent of their 2022 precipitation successful 1 day, according to the National Weather Service.

Nearby Oakland nabbed it wettest time since records began successful 1970, with 4.75 inches of rain. Redwood City saw 4.88 inches, its third-greatest regular full successful the past 116 years.

Flooding was reported successful galore locations successful Northern and Central California connected Saturday. In San Ramon, eastbound of San Francisco, the occurrence section tweeted that it responded to much than 100 flood- and storm-related incidents. Flood warnings were besides issued astir Sacramento, where up to 3 inches of rainfall fell.

More rainfall is coming to California, which is invited considering the state’s long-standing severe drought. However, the further precipitation connected saturated crushed besides poses the hazard of much flooding.

A fast-moving strategy coming Monday nighttime into Tuesday is expected to driblet a speedy half-inch oregon truthful successful chiefly successful the cardinal and bluish parts of the state. It volition beryllium followed by a much robust and slower-moving tempest strategy that has the imaginable to dump astatine slightest 2 to 3 inches of rainfall Wednesday and Thursday.

The storminess is owed to a parade of atmospheric rivers, oregon conveyor belt-like corridors of tropical moisture with origins arsenic acold distant arsenic Hawaii. Each reaches California done the aforesaid basal processes: Each filament of moisture is drawn eastward successful betwixt 2 oppositely spinning upwind systems — a counterclockwise-rotating debased to the north, with clockwise-spinning precocious unit successful the tropics to the south. The 2 systems enactment unneurotic similar meshing gears, tugging ribbons of soupy tropical aerial toward the east.

Atmospheric rivers transportation their heaviest moisture astir a mile supra the ground, which is wherefore higher elevations, similar the Coastal Range and the Sierra Nevada, ordinarily extremity up with the jackpot precipitation totals. Saturday’s setup was a spot antithetic — what began arsenic an atmospheric stream transitioned into much of a classical soaking rainfall lawsuit arsenic a halfway of debased unit passed overhead. That brewed downpours and isolated thunderstorm activity, which led to higher rainfall rates.

During a three-hour model successful San Francisco betwixt astir 10 a.m. and 1 p.m., the airdrome measured 2.63 inches of rain.

High precipitation rates were besides a staple of the snowfall that accompanied the strategy successful the Sierra Nevada. Snow fell predominantly supra 7,000 feet successful elevation, with exceptional accumulations supra 9,000 feet.

The U.C. Berkeley Central Sierra Snow Lab, which researches Sierra snowfall and h2o resources, observed snowfall rates arsenic precocious arsenic 7.5 inches per hr Saturday afternoon. An on-site researcher noted that the snowfall was airy and fluffy, with frigid temperatures boosting the “fluff factor” of the snow.

While storms similar this bash periodically occur, dense precipitation rates are made much apt by the effects of human-induced clime change, which is warming the atmosphere.

As the ambiance heats up, the aerial tin clasp much water. When moisture is unavailable, that translates to a desiccated scenery and drought. But erstwhile tempest systems present moisture, arsenic was the lawsuit Saturday, the ambiance tin store and unload much water, starring to higher precipitation totals.

The frequence of top-tier, heavy-rain events is expanding markedly, adjacent if wide precipitation totals implicit a twelvemonth whitethorn not grounds the aforesaid trend. Days with 2 inches oregon much of rainfall astatine San Francisco International Airport are much than 60 percent much communal nowadays compared to the 1950s.