Sunrise light on a grove of tufa towers emerging from the water of Mono Lake with soft green and dusty-red wild grasses in the foreground, Canada geese in the shallow water with reflections of the rocky towers, and desert hills in the distance.

Two-month dry spell ends with latest closure of Tioga Pass ever

Following a wet October and a dry November, there were only 3 days in December with a trace of precipitation in Lee Vining. Going into January, the season was at only 33% of average when measured at the NOAA rain gauge at the Mono Lake Committee Information Center & Bookstore. 1989, 1990, 1993, 1997, 1998, 1999, and 2000 were all years with similar or drier autumns, adding up to almost 1/3 of the 24 years on record at our weather station. But it was the first half of January that threw this season into the remarkable category.

On January 17, 2012, Tioga Pass finally closed for the winter as storm clouds gathered on the horizon. The only other time in history—going back to 1933—when it closed in January was when it closed on New Year’s Day 2000.

On January 21st, 2012—exactly two months since the last measurable precipitation on November 21st—we recorded rain and snow in Lee Vining! By the end of the weekend, 2.39 inches of precipitation and 11.2 inches of snow fell, bringing the month of January up to 81% of average and the season up to 53% of average to date—and 34% of the October–March average. No more storms are in the forecast for January. Only 1988–1989, 1989–1990, 1990–1991, 1993–1994, 1997–1998, 1999–2000, 2000–2001, 2006–2007, and 2008–2009 had a drier season as of the end of January. 1998 was the only one of those years that ended above average—and the next-closest was 1989 with 77%.

If February and March are average, the winter  season would end at 70% of average precipitation in Lee Vining. Either our wettest February or our wettest March on record would put us over 100% for the season. A series of very wet storms could do just that—like in 1998—but it is a long shot at this point. Get ready for a dry year.

But not the driest. The entire 1991 water year (Oct. 1, 1990–Sept. 30, 1991)delivered only half of the precipitation to Lee Vining that we have so far.

At Gem Pass, the snowpack is 36% of average (source: Cain Ranch precipitation here is incorrect due to a power outage), however Dana Meadows is reporting much more, indicating a very uneven distribution of the recent snowfall. We will have to wait for the February 1st, March 1st, and April 1st snow surveys to get a better idea of what the runoff might be like this year.

Mono Lake’s 2-foot rise last year will be eroded if this turns out to be a dry year—by as much as 1.5 feet if we have a year as dry as 2007. We need back-to-back wet years if Mono Lake is to rise rapidly. Preliminary modeling results show that if a repeat of the early 1980s hydrology were to occur, with a string of five wet years in a row, Mono Lake would reach the target 6391 feet above sea level in just five years. It is a long shot, but it could still happen by 2016 if the next two months are wet!


  1. Plotting the Tioga Pass closure dates since 1933 provides a powerful graphic of our changing climate. Oops, I almost said “Climate Change.” How politically incorrect of me.

  2. Dan – yes, good point, I should have said “liquid precipitation.” Essentially it is melted snow plus any rain that we are measuring separately from the snowfall depth. Bill – changing technology, road configuration, and park policies also influence the closing date in addition to the changing climate.

  3. Hi Greg; thanks for setting Bill straight. Have you given up on the weather data from your instruments and we now will just use the NOAA data? If so I would still like to see the wind data.

  4. Greg and Bob: Agreed that many changes influence road closure dates. Still, the data stands for itself, and encourages a serious consideration of our changing climate, rather than an offhand opportunity to disregard evidence of man’s continuing environmental impacts. Just another brick in the wall.