In the West, precipitation — rain combined with the water equivalent of melted snow — is measured in water years as opposed to calendar years. In California, the water year runs from Oct. 1 to Sept. 30. Historically, early October is the time of minimum stream and reservoir levels in the Golden State, as well as the start of the rainy season. There is still time left in our water year, but statistically September brings little precipitation so we’ll go with our current totals.
This past winter set a few snowfall totals, but its 47.6-foot snowfall tally measured at Donner Pass ranks only 17th, tied with 1911. That is still about 4.5 feet shy of 1981-82, which holds last place on the Top 10 snowfall list. (Read my book “SNOWBOUND! Top 10 Biggest Winters of the Tahoe Sierra.”)
Hydrologically, however, this water year blew away all records when it comes to precipitation. At Donner Pass, the 118 inches of water — nearly 10 feet — is by far the wettest winter of record, easily surpassing former No. 1 in 1982 at 112 inches. The unprecedented storm pattern raised Lake Tahoe about 6.5 feet, the all-time greatest seasonal rise for Big Blue.
The unprecedented storm pattern raised Lake Tahoe about 6.5 feet, the all-time greatest seasonal rise for Big Blue.
October 2016 shot out of the gate mid-month with an intense atmospheric river that drenched the region. While the Tahoe Sierra experienced rain, the summit area of Mount Shasta above 12,000 feet was hammered with 20 feet of snow in less than five days. More storms before Halloween dropped several more inches into the bucket. Tahoe City set a new October record with more than 9 inches of rain at 437 percent of normal. Donner Pass picked up about 14.5 inches of precipitation; its average is 3.3 inches. November precipitation was also above average with about 6.5 inches on Donner Pass.
The upper mountain at Squaw Valley picked up 4 feet of snow that month, complementing the man-made flakes it had generated on its groomed runs. In December, more warm, wet Pacific storms added another 12.5 inches of water to the gauge, even as the Sierra snowpack failed to get much traction because of high snow levels due to the subtropical nature of the moisture feed.
Throughout much of winter 2017, a persistent low-pressure system rotated counter-clockwise off the coast of British Columbia and the Pacific Northwest. This atmospheric pattern entrained moisture from out in the Pacific Ocean and pumped it repeatedly into Northern California. Typically, the region is affected by about five atmospheric river (AR) storms, known colloquially as a Pineapple Express, which deliver about 30 to 50 percent of the annual precipitation on the West Coast. In 2017, there were about a dozen ARs, many of them in the strong to very strong category. Over the course of seven months, the winter became a relentless pounding that damaged infrastructure, killed power for days and left many locals reeling.
The first week of December was dry, dominated by a cold wave. It was one of the very few that occurred during this relatively mild winter. On Dec. 10, a series of potent storms of the AR type surged into the region, compelling the Reno office of the National Weather Service to issue a flood watch for the greater Lake Tahoe, Truckee and Reno areas. It poured rain as freezing levels often ranged above 7,500 feet. More than a foot of water soaked Donner Pass that month, but only 14 inches of snow. Testament to the temperate nature of these storm systems, Squaw Valley tallied only 35 inches of snow on its upper mountain in December despite abundant precipitation.
The historic winter of 2017 was off to a roaring start on a record-setting trajectory, but in overview the month of January is the crown jewel in this atmospheric freak show. If you’re looking for snowfall records, January 2017 has them.
It stormed for nearly three consecutive weeks that month. This time snow levels were below 6,000 feet where most residents and visitors live, travel and congregate. In the first week, more than 7 feet of snow piled up at local resorts. Another intense AR with enough cold air support quickly followed that so that precipitation remained frozen near 6,000 feet.
Rare blizzard warnings were posted for regional highway passes such as Donner and Mount Rose as winds exceeded 150 mph over mountain ridges. From Jan. 2 to 13, more than 15 feet of snow smothered the high Sierra; up to 8 feet fell on Tahoe’s West Shore. At this point the snowpack was double normal. A third storm pummeled the region with another 7 to 8 feet in just five days. It was overwhelming for road and utility crews, as well as for ski patrol. Some of the bigger resorts were closed for extended periods of time.
Over the course of January, impacts included multiple fatalities, collapsed buildings, rampant avalanches, extended power outages, closed roads and highways and day after day of school closures. Squaw Valley and other Tahoe Sierra resorts were dumped with more than 23 feet of snow that month, many setting new records. In Nevada, Mount Rose Ski Tahoe garnered its own new monthly snowfall record with 295 inches or 24.6 feet.
At the Central Sierra Snow Lab near Donner Pass, station manager Randall Osterhuber tallied 237 inches that month, which eclipsed by 3 feet the former snowiest January in 1982 with 175 inches. The lab also set a snowfall record for any month, beating the legendary Miracle March of 1992 that had picked up 201 inches. It was also very wet at the lab with more than 32 inches of precipitation.
And the storms kept coming. On Feb. 21, the anemometer at the top of Alpine Meadows was hit by a wind gust of 199 mph. By the end of February, Tahoe City set a new October through February record with more than 56 inches of precipitation — the annual average is 31.5 inches — that beat the previous record from 1969 by 10 inches.
Lake Tahoe had been pumped with nearly 139 billion gallons of water since October, enough to supply 425,000 American families with water. Ultimately, Olympic Valley’s upper mountain total reached 728 inches, an astounding 60-plus feet of snow. But even that couldn’t outshine the La Niña-influenced winter of 2011 when 810 inches or 67.5 feet of snow pummeled the resort, just five years before.