Californiaâs water supply is looking a lot more robust after an atmospheric river blanketed the Northern Sierra Nevada with snow.
Last weekâs storm deluged Mammoth Mountain with nearly 9 feet of powder and enveloped Kirkwood, Alpine Meadows and Squaw Valley with about 7 feet of fresh powder.
What a difference 10 days makes!
Jan 20th 2021 vs Jan 30th 2021 #SnowPackGainz pic.twitter.com/OZmLRcUNNs
— NWS Reno (@NWSReno) January 30, 2021
But all that white stuff wasn’t quite enough to push the stateâs snowpack above average for this time of year. Thatâs due to more than a year of dry weather, and during rainy season in 2020, the state saw just 39% average rainfall the last three months of the year.
Measurements from officials with the California Department of Water Resources show the snowpack near Lake Tahoe at about 93% of Februaryâs historical average.
Sean de Guzman, chief of DWR’s Snow Surveys and Water Supply Forecasting Section, recorded a snow depth of 63 inches and a snow-water content of 17 inches at Phillips Station snow course, south of Lake Tahoe.
The statewide automated snow sensor network as of Wednesday morning reported the snowpack at 70% of average.
âThe state has experienced a series of storms over the last couple of weeks that brought a significant amount of rain and snow,â de Guzman said. âHowever, these storms were not nearly enough to make up the deficit that we have accumulated over the last few months.â
A sustained La Niña, which is cold water on the surface of the Equatorial Pacific that affects weather across the globe, has held a ridge of high pressure over California and forced storms that might normally have pelted the state over the Pacific Northwest instead.
Reporter Paul Rogers of the Mercury News notes Californiaâs current water story needs to be told in two parts.
While the recent atmospheric river brought blizzard conditions across the Sierra, the Bay Area is âstuck in one of the worst two-year rainfall deficits seen since the 1849 Gold Rush,â Rogers writes.
At the beginning of February, San Francisco had received only about 17 inches of rain since July 1, 2019. From the Mercury News:
…San Francisco is 20.13 inches behind normal for last winter, and this winter so far, combined. That makes the past 19 months the third-driest such period in San Francisco in 172 years, when records first began in 1849…. The only two similar 19-month periods that were drier than the current one were from July 1975 to January 1977 â the middle of a historic drought â and July 1897 to January 1899. The rainfall deficit is drawing increasing attention from water managers, who say that unless February and March bring numerous major storms to boost reservoir levels, water restrictions may return to Northern California communities this summer.
âLast year we began digging a big hole. And this year we continued digging,â meteorologist Jan Null told Rogers. âWe would need something monumental and probably catastrophic to get out of it.â
Meteorologists say Californiaâs February rain outlook does not look good, with high pressure and a likely return to below average precipitation for two weeks, at least.
…Then, high pressure will build once again near West Coast–bringing a period of much drier conditions. This will be a relatively cool pattern, & there could be an occasional chance of showers in north, but ensembles are suggesting a 2-3 wk period of below avg precip. #CAwx pic.twitter.com/lgz1YlBVrU
— Daniel Swain (@Weather_West) January 31, 2021
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