Historic perspective on storm size

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The intense storms that buried the Sierra Nevada in much-needed snow this past weekend were well advertised by the National Weather Service and media. Warnings of potential blizzard conditions and life-threatening road conditions were posted days in advance. Previous weather systems this winter were disappointing considering their forecasted snow production, but everyone was taking this series of storms very seriously.Sometimes I wonder about the irrational exuberance that occasionally accompanies the NWS winter forecast discussions, but the extreme wind speeds (exceeding 100 mph on mountain ridges and 70 mph through the highway passes) and heavy snowfall expected with the Friday system warranted dangerous storm headlines. The combination of the tightly-wrapped low-pressure system and a powerful 200 mph jet stream ripping across the region was dangerous and potentially deadly. Another important factor in the hyped-up weather warning was the number of tourists and visitors still enjoying their holidays in Truckee and the Tahoe Basin. The potential for extended road closures on the major trans-Sierra highways was a very real possibility and our holiday guests should be warned in advance that this might not be the best series of storms to ride out like a hurricane party. There was a lot of excited hyperbole among NWS forecasters and the media about how the spate of storms could generate snowfall of historic proportions. (Unfortunately, I am writing this story to meet my deadline and the first of the three expected storms is just hitting the California coast, so by the time you read this column the three storms, and their impact, will be history.) But whenever an exceptional storm pattern pounds the region, many wonder if it was the most powerful in a century, a decade, or just the biggest snowfall since a lot of new folks have moved to the region? As is often the case with major weather events, the correct answer depends on your perception and location. Now that those systems have roared east, its time to take stock and put the recent weather event in perspective. You dont have to be longtime local to remember that it was just three years ago the region was inundated with a series of powerful storms that were widely declared to be the worst on record. Snowfall numbers were very impressive in the Sierra, but not quite record-setting. Between Dec. 28, 2004, and Jan. 11, 2005, National Weather Service cooperative observer Don Huber recorded 98 inches of snow near the Truckee Ranger Station. During the same time span, observers in Tahoe City reported 118 inches of snowfall. Compare that to the 130 inches measured in Tahoe City in January 1911 during a four-day storm, or the 108 inches recorded during another four-day event in January 1952. Randall Osterhuber, manager of the Central Sierra Snow Laboratory (CSSL) near Donner Pass, tallied 155 inches of snowfall during the 2005 barrage. Thats 12.9 feet of snow in 15 days, but there have been other storm periods that dumped more at the CSSL. Close to 14 feet was measured at the lab after an 11-day storm in January 1969, and that was exceeded in 1982 by a 15.5-foot snowfall over 13 days. The extended storm period in 2005 actually consisted of two individual, low-pressure systems, and there was a short, but distinct break between the two. (Note: At the CSSL trace amounts of snow were measured during the break, which could place the recent snow event in the single storm category at that location.) Either way, the weather record indicates even more intense snowfalls in our region. In February 1999, Sugar Bowl Ski Resort was blessed with an impressive 14 feet of powder in a potent three-day storm. Californias single storm snowfall record was set in February 1959 when Mount Shasta picked up 15.75 feet in just six days. Although the data are unofficial, it is estimated that 14.5 to 16.5 feet of snow fell in Nevada at Tahoe Meadows (8,500 elevation) near Mount Rose from Feb. 12 – 20, 1986.After the storm event in January 2005, local resorts reported anywhere from 12 to 19 feet of fresh snow. Squaw Valley totaled 12.5 feet new accumulation at the 8,200-foot level during the storm period, while other resorts claimed much more. The wide range in snowfall tallies were caused by the high winds prevalent during the event, as well as the methodology used to measure the snow. The National Weather Service standard is to measure snowfall every six hours that’s four times every 24-hour period and the maximum limit for official data submitted by either NWS staff or cooperative observers. Fewer measurements are acceptable; more voids the data. Central Sierra Snow Lab scientists measure the snow twice a day, every 12 hours, while at Homewood Mountain Resort, the ski patrol records the buildup on their snowboard just once a day. Some ski areas may measure snowfall more often. Snow depth can change rapidly from warming temperatures, rain or compaction. In general, the more often snowfall is measured, the greater the amount totaled. In January 2005, the national and regional media reported that the rain and snow generated by the West Coast storms were the greatest in recorded history. For Los Angeles and Reno, that claim had merit. Torrential rain in Southern California broke several long-standing records for precipitation and took the lives of more than 20 people due to floods and mudslides. In Reno, the 2005 event was the most snow since a series of cold storms during January 1916 buried the Biggest Little City with 65.7 inches. That record stood for 89 years until the 79 inches of snow recorded by the NWS office in the hills north of Reno blew it away. Not only was the total snowfall greater from the 2005 event, it occurred in a much shorter period of time. In 1916, precipitation fell on 21 days throughout the calendar month, versus about two weeks in 2005. NWS observations from the Reno metro area and surrounding foothills indicate that the recent snowfall ranged between 6 to 7.5 feet. Those snowstorms exceeded the Jan. 1916 total handily, but Reno failed to break the all-time seasonal snowfall record of 82.3 inches set in 1915-1916.La Nia-influenced winters are known for major flood events so we dodged a potential bullet with this recent weather event. As the Alaskan-bred storm system tracked slowly down the West Coast in early January 2008, it tapped into a deep tropical moisture plume that generated heavy precipitation over California. Fortunately for Tahoe-Truckee resorts, the cold core of the storms lowered snow levels and saved us from a significant high-elevation rain event. More importantly for those of us who live, work and play in the Tahoe/Truckee region, our snowpack has improved dramatically, thus ensuring many more weeks of winter sports and satisfied visitors. For a complete list of historic Sierra snowfall records, visit Mark’s Web site at http://www.thestormking.com.
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