Big storm’s 7 feet of snow not enough
Rain expected to arrive in Bay Area today but still won’t alleviate very dry winter
A major storm system is forecast to slam into California from Alaska and Canada starting tonight, bringing soaking rain to the Bay Area on Thursday and dumping up to 7 feet of new snow to the historically dry Sierra Nevada by Saturday.
But as welcome as the snow is during a very dry winter so far, it won’t be enough to return the Sierra Nevada — the source of 30 percent of California’s water supply — back to its average for the year, experts said Tuesday.
“This should be the largest storm of the year so far. The sheer amounts are impressive,” said Eric Kurth, a meteorologist with the National Weather Service in Sacramento. “But this one storm is not going to solve the issues of this year. It’s not going to be a complete turnaround on its own. If we want an average year, we are going to need a number of significant storms more like this.”
It comes down to simple math.
On Tuesday afternoon, even after some moderate snow on Monday that had ski resorts cheering, the statewide Sierra snowpack — which also includes the Mount Shasta area — stood at just 23 percent of average, according to the state Department of Water Resources. That’s on pace to be one of the five worst March 1 readings since 1950 when modern records began.
More important, that small amount of snow is holding just 6 inches of “snow water equivalent,” or 6 inches of water if it was melted. The historic Sierra average for March 1 is about 25 inches and on
“This should be the largest storm of the year so far. The sheer amounts are impressive. But this one storm is not going to solve the issues of this year.” — Eric Kurth, a meteorologist with the National Weather Service in Sacramento
April 1 at the end of the winter season, about 30 inches.
California’s hydrologists estimate that every 10 inches of snow produces about 1 inch of water. So to get to an average March 1 reading, the Sierra Nevada would need 19 more inches of water — or 190 inches of snow — this week. That’s nearly 16 feet of snow. And 24 inches by April 1, or 20 feet of new snow over the next five weeks.
This week’s storm will make up some, but not even half, of that deficit. The big amounts forecast in the storm that will arrive today, peak on Thursday and continue into Friday and early Saturday are up to 7 feet at Carson, Ebbetts and Sonora passes in the Sierra Nevada, 4 to 5 feet at Donner Summit along Interstate 80 and 3 to 4 feet at Lake Tahoe.
“We definitely have had record low snowfall this year,” said Kevin Cooper, a spokesman for Kirkwood and Heavenly ski resorts near Lake Tahoe. “A few weeks ago we were at the lowest in history. The good news is that the storm door is opening again. We’re starting to see snow. And now we’re looking at a lot of snow in a very condensed amount of time.”
The snowfall is expected to be so heavy that the Department of Water Resources canceled its
monthly snow survey for Phillips Station near Lake Tahoe, and moved it to Monday, fearful that TV trucks and others attending the event would get stuck in blizzard conditions.
“These events are going to improve things considerably. It might well double the amount of snowpack we have,” said Thomas Painter, a principal scientist at NASA’s Jet Propulsion Laboratory in Pasadena who leads research on Sierra snow trends.
“But we’ve got to have a lot more like this just to get back to average,” he said.
This week’s storms might take the snowpack from 23 percent to about 40 percent, a significant boost that comes as many water experts were wondering whether the state might be heading back into a drought after a very dry, warmerthan-normal winter. But if March does not have four to six more storms like this one, the Sierra snowpack could still end up among the lowest in history, like the winters of 1976-77 or 2014-15, Painter said.
Luckily, from a drought standpoint, last winter’s massive rains filled most of the state’s reservoirs, so it will take less rain and melting snow this year to top them up again.
“We’re above the historic average on one reservoir after another,” said Doug Carlson, a spokesman for the Department of Water Resources. “With that much water stored in the major reservoirs, I think it
would be inappropriate to say that the situation is serious, especially since we still have the potential for more rain and snow in the month ahead.”
Still, Carlson noted the state got off to a very bad start this winter.
“There’s no denying that this winter to date is very close to what we saw in 2015,” he said, “the worst year ever for a snowpack.”
Across the Sierra, places normally deep in snow have been sparsely covered.
“There’s a lot of patchy snow cover and ski areas that are muddy instead of snowy,” said Roger Bales, director of the Sierra Nevada Research Institute at UC Merced. “Winter recreation as well as water supply are hurting. I haven’t even waxed my skis this year.”
Bales noted that even with last year’s big snow storms, temperatures were warmer than in years past, and the snow line was about 500 feet higher in many places on average. This week’s storms are colder, driven by frigid air from western Canada and Alaska, and should bring snow on Thursday to as low as 1,000 feet in some parts of Northern California, meaning more snow on Bay Area peaks and Sierra foothill communities is likely.
In the Bay Area, rain is expected to arrive today in the North Bay and spread across the area by late tonight. By Thursday, rains will be heaviest, forecasters
say, disrupting the morning commute and continuing through the day with gusty winds and low temperatures in the high 30s and highs in the mid-50s. The weather service expects up to 1 inch of rain in most Bay Area cities by Thursday night, with 1.5 to 2 inches in the Santa Cruz Mountains and Big Sur hills.
The storms cannot come soon enough for California. Having just recovered from the 2012-2017 drought, most major cities are well below their historic rainfall totals. San Jose on Tuesday stood at 43 percent of average, Oakland at 54 percent and San Francisco at 50 percent. To the south, conditions have been historically hot and dry. Los Angeles on Tuesday had received only 1.9 inches of rain since Oct. 1 — bringing its winter total to just 18 percent of historic average, with San Diego at 27 percent and Irvine at 11 percent.
The good news: Computer models show that there is a chance of more rain and snow next week. Will that lead to a “March Miracle” like the one in 1991 that boosted the Sierra snowpack from 18 percent on March 1 to 83 percent a month later?
“Those don’t happen very often,” said Kurth, the weather service meteorologist. “They are rare. But they are possible. At least we’re on track to start the month wet.”