Avalanche! – Tahoe Nuggets

TAHOE NUGGET #268: SQUAW VALLEY
AVALANCHES

Heavy rain and snow in the past week has not
mitigated the extreme drought conditions in northern California, but it pumped
up Lake Tahoe’s low water levels and gave a much needed boost to Tahoe ski resorts
that had been limping along on life support.

Commonly known as a “Pineapple Express”
storm, the National Weather Service now refers to them as “atmospheric river
events” when describing a subtropical moisture surge from the Pacific Ocean. These
juicy systems can produce phenomenal rainfall totals, often exceeding 20
inches. This one did not, but the 10 to 15 inches that soaked the Sierra west
slope over 4 days raised an important reservoir in Sacramento by 20 feet in a short period of time.

Lake Tahoe’s rise of about 5.5 inches in less than a week is the equivalent of 17.2 billion gallons of water or 53,000 acre-feet. That’s enough water to cover 83 square miles of land to a foot deep, about the size of Seattle, Washington.

Tahoe City picked up more than six inches of
rain while the upper mountain at Squaw Valley was hammered with five to six
feet of new snow. Kirkwood Mountain Resort near South Lake Tahoe was walloped with nearly 9 feet of snow in one week. Avalanche conditions in the backcountry are extreme. The
danger of Truckee River flooding never materialized as snow levels failed to
rise as high as predicted, which kept much of the precipitation as snow above
7,000 to 7,500 feet.

I apologize in advance to my subscribers back
east who probably have no desire to see photographs of ice or snow of any kind.

During this warm storm, snow levels were projected to rise higher than the major passes of Donner (I-80) and Echo (Highway 50) between California and Nevada. Precipitation at Echo Summit (7,382′) turned to rain, but snow and ice persisted on Donner Pass ((7,227′) as seen here on Feb. 8, 2014. Mandatory chain controls were in force for one of the few times this winter so far.

Fresh snow at Squaw Valley finally has the ski area looking like the world class resort that it is.

Ski patrollers keep portions of the mountain closed until all potential slides have been triggered. It is easy to imagine the deadly force that avalanches pose to skiers and snowboarders. Note skiers to the right of debris field.

Due to the heavy, wet nature of the storm and the sheer volume of snow that fell in a short period of time, much of the upper slopes at Squaw Valley were extremely unstable. Note Siberia Express chairlift tower upper right.

Wall of snow hammered trees and overran a groomed area. Note 3-foot avalanche crown below ridgeline.

Note recent dramatic spike in precipitation for the Northern Sierra for this water year so far. We still have along way to go, but snow is predicted for this weekend and it’s looking likely that a potent and cold system will hit next week.

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TAHOE NUGGET #230: WINTER OF 1982

It’s been 30 years since one of the deadliest avalanches in Sierra Nevada history broke loose at Alpine Meadows Ski Resort and killed seven people. For those of us who remember this tragic event on March 31, 1982, and the days of grief and hope that followed, it represents a benchmark in time. The 15.5 feet of snow that fell at the Central Sierra Snow Lab between March 27 and April 8, 1982, still ranks as the greatest single snowstorm total on record for Donner Summit.

Miraculously, Alpine Meadows employee Anna Conrad survived for 5 days in the avalanche debris before she was rescued. She lost parts of both legs to frostbite, but after the surgery she was fitted with prosthesis. Today, she and her husband reside at Mammoth Lakes, California, where Anna is employed as a snow hostess for the resort.

Anna (Conrad) Allen survived the 1982 avalanche at Alpine Meadows. She suffered frostbite injuries, but later moved to Mammoth Mountain where she lives with her husband.

For anyone who skis or snowboards today, whether backcountry or controlled resort, the 1982 avalanche still serves as a reminder that the rugged mountains and dynamic weather we love so much are powerful forces of nature that deserve respect and understanding.

Read a short version of the story here: Tahoe Nugget #60

The winter of ’82 was also noteworthy for an extreme precipitation event that occurred in January. From Jan. 3-5, torrential rains caused extensive damage and destruction in the lowlands of the central and northern parts of California and heavy snows fell in the highest mountains. The San Francisco-Bay Area experienced the heaviest rainfall in 25 years. On January 4, San Francisco was doused with 6.16 inches of rain which is still the greatest one day storm total there in 159 years of rainfall records.

The Santa Cruz Mountains were inundated with 10 to 20 inches of rain in 30 hours. The National Weather Service reported more than 8 inches of rain in one day there, the greatest 24-hour rainfall since 1890 when record keeping began. Considered one of the worst storms of the century, several thousand people were flooded out of their homes and at least 33 killed. Trains derailed, schools and highways were closed, and damage was estimated at $300 million.

Avalanche path near Mt. Tallac at South Lake Tahoe.

When the saturated air mass encountered the Sierra Nevada, precipitation intensified due to topography and orographic enhancement. The Echo Summit weather station at Sierra Ski Ranch, elevation 7,450 ft., is approximately ten air miles southwest of South Lake Tahoe, on the upper western slopes of the Sierra Nevada. The station is located near the Sierra Nevada crestline in an area where the well-defined ridge has a northwest-southeast orientation. Situated on a north-facing slope, the site is a choice area for maximum snowfall production.

24-hour snowfall of 67 inches set a new California record in January 1982.

Weather maps of this event indicated a strong zonal flow with very moist air moving west to east across the Eastern Pacific. This juicy fetch of moisture from the southwest collided with colder air flowing down the eastern side of a high-pressure system centered over the Gulf of Alaska. At Echo Summit, 67 inches of snow (5.6 feet) fell in just 24 hours, which ranks it as the second greatest single day snowfall total in the United States. The North American and world records are held by Silver Lake, Colorado, which received 76 inches (6.3 ft.) in 24 hours on April 14-15, 1921.

Overnight snowfall in the “banana belt” neighborhood of Gateway west of downtown Truckee.

The Jan. 4-5 storm that dumped up to five feet of snow in the mountains was only one in a series of powerful snowstorms that had been hammering the Sierra Nevada over the New Year’s Holidays. The Central Sierra snowpack exceeded 11 feet in depth, and nearly a dozen avalanches had roared through the Donner Summit. Thousands of motorists were stranded when highway crews shut down Interstate 80. The two-day total of 80 inches (Jan. 3-5) recorded at Echo Summit during this 1982 event ranks third in California.

The Tahoe snowpack was huge by mid-April 1982. My brother Tom came out for a visit in March and ended up staying an extra week because we couldn’t get to Reno for a departure flight.

Interestingly, just three months after the Jan. 1982 event, on March 30-31, a 65-inch snowfall was recorded in 24 hours at Twin Lakes, California, only eight miles south of Echo Summit. The two-day total from March 30 to April 1, 1982, at Twin Lakes was 90 inches, the second greatest 48-hour snowfall total in U.S. history.

On January 11-12, 1997, Montague, New York, located just east of Lake Ontario, reported a new record of 77 inches in 24 hours. The measurement was disallowed, however, after the National Climate Extremes Committee determined that the total was achieved by adding six measurements together, two more than the maximum allowed during any 24-hour period.

Town of Truckee during the big storm that caused the Alpine Meadows avalanche.

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