An atmospheric river created by a low-pressure system off the Pacific Northwest is expected to drench Fresno today as it eventually spreads to Los Angeles by Tuesday night.

A Category 4/5 atmospheric river is barreling towards the West Coast.

This will begin a parade of storms for California that will last into 2023, dropping widespread heavy rain statewide and FEET of mountain snow. pic.twitter.com/IGiKrYGd0f

— Colin McCarthy (@US_Stormwatch) December 26, 2022

The National Weather Service in Hanford says that at least three-quarters of an inch of rain could fall today and the rain gauge could eclipse more than an inch by midnight.

Patchy fog and partly sunny skies are likely on Wednesday with showers on Thursday. According to the NWS, significant rain is in the forecast again for Friday and Saturday.

Sunday, which is New Year’s Day, comes with a 20% chance of rain. The expected high for New Year’s Day is 53 degrees.

An atmospheric river is a weather system that moves high concentrations of water vapor outside of the tropics. This atmospheric river could be as strong as a Category 4 on a scale topping out 5, the NWS said.

Winds up to 100 MPH in Sierra

The atmospheric river impacted northern California, the Sierra Nevada, and the coast early Tuesday. Downtown San Francisco had received more than an inch of rain by early morning and Mount Tamalpais had more than 4 inches before dawn.

The greater Lake Tahoe area and Mono County were warned to expect heavy snow with wind gusts around 50 mph, and up to 100 mph along Sierra ridgetops. Lake Tahoe was expected to have waves that could capsize small vessels.

The weather service issued Winter Storm Warnings for the Sierra Nevada, where motorists were advised that the combination of winds and snow could make travel hazardous.

Chains controls were put into effect on I-80 over Donner Summit, but the California Highway Patrol reported that they were lifted at about 7:30 a.m today. However, the CHP advised travelers that snow levels were expected to drop later Tuesday.

❄️❄️ UPDATE ❄️❄️

12/27/22 7:30am

Well that was quick!! Chain control has been lifted on I-80 over Donner Summit. At the moment, we are getting significant rain fall but snow levels are expected to drop later today and in the evening. pic.twitter.com/SLXN45jqII

— CHP Truckee (@CHP_Truckee) December 27, 2022

Fresno Rainfall Totals

Through Monday night, Fresno had received 3.25 inches of rain since Oct. 1, or 113% of “normal” for the date. Last year, at this time, Fresno had received 4.70 inches of rain. But drought resumed when the calendar turned to January.

Snow sensors indicate that California’s snow water content is 145% of normal through today and 163% of normal for the Southern Sierra.

Crews are very busy sweeping streets, filling potholes, clearing broken branches and on flood control unclogging drains.

Need to report any of the above? Report it now by calling 311 or downloading our FresGO app. ☎️ pic.twitter.com/4pwFvLUdNu

— City of Fresno (@CityofFresno) December 27, 2022

Reservoir Totals

As is often the case, Millerton Lake is fuller than the state’s other major reservoirs. Its water level was 69% of capacity and 135% of normal for the date as Sunday night.

Pine Flat, which at 1 million acre-feet, has nearly twice the capacity of Millerton, has filled to 22%. That is 65% of normal for the date.

Both reservoirs are expected to come up significantly with this week’s storms, as is San Luis Reservoir.  San Luis is holding 618, 121 acre-feet of water — or about 31% of capacity.

(Associated Press contributed to this story.)