Storming the facts

Were the recent monster storms that buried the Sierra and western Nevada in deep snow the most powerful in a century, a decade—or just the biggest 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 perception and location. Now that those systems have roared east and high pressure is back in control, it’s time to take stock and put the recent weather in perspective.

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 just west of Donner Pass, tallied 155 inches of snowfall during the barrage. That’s 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 there in 11 days in January 1969, which was exceeded by a 15.5-feet snowfall over 13 days in 1982.

Winter storm(s)

The recent extended storm period actually consisted of two low-pressure systems, and there was a short but distinct break between the two. On the other hand, 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 14 feet of powder in a potent three-day storm.

California’s 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-foot elevation) near Mount Rose from Feb. 12-20, 1986.

Local resorts are reporting anywhere from 12 to 19 feet of fresh snow. The wide range in snowfall tallies may have to do with 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 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.

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 has 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, it was the most snow since a series of cold storms during January 1916 buried the city with 65.7 inches. That record stood for 89 years until the new total of 79 inches recorded in the hills just north of Reno blew it away.

Not only was the total snowfall greater from this event, it fell in a shorter period. In 1916, precipitation fell on 21 days throughout January, versus about two weeks this time.

NWS observations from the Reno metro area and surrounding foothills indicate that the recent snowfall ranged between 6 to 7.5 feet. These snowstorms exceeded the January 1916 total handily, but Reno still has a few inches to go to break the all-time seasonal snowfall record of 82.3 inches set in 1915-16. Fortunately, there is still plenty of time left this winter to take the title.

Blame or credit

What caused the exceptional weather? For months, meteorologists have been watching a weak El Niño event simmering in the Pacific Ocean, but it turns out National Oceanic and Atmospheric Administration scientists believe they have found the primary cause for the epic event.

“A leading climate culprit is the Madden-Julian Oscillation, or MJO,” said Wayne Higgins, lead climate specialist at the NOAA Climate Prediction Center. (The term culprit suggests blame, but in a drought, such storms can be good news.)

The MJO is a tropical disturbance that can affect patterns of tropical rainfall and produce El Niño-like features that can influence extreme precipitation events in the Western United States. According to NOAA, typically the MJO is most active during weak El Niño winters such as this one. As the two powerful storm systems tracked slowly down the West Coast in late December and early January, they tapped into a deep tropical moisture plume that dramatically increased precipitation over California.

Fortunately for Tahoe-Truckee resorts, the cold core of the Alaska-bred storms lowered snow levels and saved them from significant high-elevation rain.

The Central Sierra Snow Laboratory has received nearly 23 feet of snow this water year (Oct. 1 to Sept. 30), which is about 188 percent of normal. Precipitation recorded so far is nearly 40 inches, about 167 percent of normal. (Precipitation is rain and snow melted for its water equivalent.)

More important for those of us who live and play in the Lake Tahoe and Truckee River drainage basins, our snowpack and seasonal precipitation rates are also above normal. Current data indicate that precipitation in our basins is running about 130 percent of normal for the date, while the water content in the snowpack is about 180 percent.

It’s good news for a region in the throes of a five-year drought with seriously depleted lake and reservoir storage levels. The healthy snowpack will help alleviate the desiccated conditions when it melts.

But we’re definitely not out of the woods yet. In each of the last three years, mid-January snowpack totals were soaring above average, but then all three turned out disappointing in terms of the region’s water supply. Anemic precipitation following the early strong starts coupled with warm spring weather depleted the runoff.

Now that our shoveling muscles have recovered, it’s time once again to pray for snow.