Rain and mountain snow have returned to California after the state’s driest start to the calendar year on record.
The welcome wet pattern will probably delay what would have been a very early start to fire season. But the state remains entrenched in a multi-year drought.
Nearly half of California is experiencing extreme drought, the second most severe category.
While probably too little too late, a recent pattern shift has steered a series of Pacific storms into the northern part of the state.
More than three feet of snow has fallen in some locations, and another hefty storm is set to impact the region late Wednesday into Friday. The Weather Service has issued a winter storm warning for elevations above 5,000 feet in the Sierra Nevada and southern Cascades, where one to two feet of snow, and more than three feet at the highest peaks, is expected. “Mountain travel is highly discouraged,” it warned, as these areas could near white-out conditions.
A strong late season winter storm will impact interior #NorCal later today through Friday. Widespread precipitation and dangerous mountain travel conditions are expected. If you must travel, check road conditions at https://t.co/6jnhwJNN7a #cawx pic.twitter.com/HqDb8FPr5B— NWS Sacramento (@NWSSacramento) April 20, 2022
At lower elevations, rain will be widespread and heavy, with up to 3 inches in the foothill regions and up to an inch in the Sacramento Valley, the Bay Area and the Central Coast.
“Thursday looks to be the rainy day we’ve been waiting for since January with much of the Bay Area expected to see steady, soaking rains,” the National Weather Service in San Francisco wrote in a forecast discussion.
The Weather Service notes that from April 11 to 22, precipitation amounts may exceed what fell in the previous three-plus months.
While the renewed storminess may seem like a deluge, compared with this winter’s dry spell, the precipitation numbers so far aren’t extraordinary by April standards, and Southern California has remained mostly dry.
“We’re still below normal for most sites across the Bay Area for the month of April,” said Roger Gass, a meteorologist with the Bay Area office. “Additional rainfall later this week could put us above average for April — that would definitely be good news.”
Downtown San Francisco averages 1.6 inches of rain in April; so far this month it has recorded 0.72 inches. Since Jan. 1, it has seen only 13 percent of its normal precipitation. But for the water year, which began on Oct. 1, the picture is brighter: 2021-22 is not in the top 50 driest on record for the city, thanks to early-season storminess.
“The reason we are sitting where we are is because we had such a wet October and December,” Gass said. “We went from record rainfall in October and December across the region to record dry conditions in January, February and March.”
The state’s mountain snowpack has improved, and this month’s snow will probably provide a boost to water supplies. But statewide snowpack is still 30 percent of normal for the date, almost exactly what it was at this time in 2021, and not nearly enough to reverse the current drought.
“The amount of snow that we have on the ground is far insufficient to what we would need,” said Andrew Schwartz, the station manager and lead researcher at the Central Sierra Snow Lab, located at Donner Pass.
At this particular station, snow received during recent April storms has eclipsed what fell during January, February and March combined. The lab has recorded 45 inches in April, compared with 41 inches during January through March.
Did anyone order some late-season #snow? Because we've had 7.5" (19 cm) of snow overnight, 25.6" (65 cm) in the last 2 days, and 39.4" (100 cm) in the last 7 days!— UC Berkeley Central Sierra Snow Lab (@UCB_CSSL) April 16, 2022
It is still dumping out there and more is on the way this week!#CAwx #CAwater pic.twitter.com/W0wGfzKhUK
But these are far from record-breaking amounts for April, so far.
“Realistically, to this point, we’re not breaking records yet,” Schwartz said. “This is basically an average April, maybe slightly above it.”
Schwartz estimates that the site would need another five feet of snow to break the April record. That could be within reach if this week’s storm adds several feet or if the current wet pattern continues. However, the latest forecasts indicate a return to dry weather next week.
And looking at the water year as a whole, the drastic swings between record wet and record dry are unusual even for California — a state accustomed to a variable climate.
“Unfortunately, this is definitely on par with those weather extremes that we are going to expect to get more of,” Schwartz said. “Anthropogenic climate change is certainly exacerbating that and making that natural variability more severe.”