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Another year of double normal snow needed

May 22, 2014

Tioga Pass Road in early April during the driest winter on record. This road should have been covered in about ten feet of snow in April, when the snowpack is considered to be at its deepest. Instead, it was dry and bare almost all the way to the pass, which lies at about 10,000 feet elevation. Photo/Wendilyn Grasseschi

Reno National Weather Service meteorologist Chris Smallcomb gave the latest update on the three-year drought and what it will take to bring it to its knees Tuesday, May 20.

It wasn’t pretty.

“We have what we call a ‘structural deficit’ in terms of moisture that is very deep,” Smallcomb said in an interview prior to his talk at the Green Church Tuesday.

That deficit is so deep that it will take a huge winter to simply catch up, he said.

“It’s going to take a full year of double the normal moisture for the Mammoth area (normal is considered to be about 40 inches of precipitation on Mammoth Pass along with about 10-15 inches of non-winter rain) to reach normal,” he said.

That translates to a winter of about 80 inches of precipitation. To put that in context, the biggest winter on record, 1982-83, dropped about 90 inches of precipitation on Mammoth Pass.

To add insult to injury, Smallcomb said, there is no clear sign yet that the drought will end anytime soon, even with all the talk about a coming El Niño winter—and perhaps a “monster El Niño” pattern—now out in the media and weather world.

“People are hoping that the El Niño winter, which we are relatively sure will happen in some form, will solve everything,” he said.

“The problem is, there have been dry El Niño years and wet El Niño years and the science just isn’t good enough yet to be able to determine which one it will be at this time.

“In fact, we will have to get a lot closer to the winter, say in September or October, to be able to have a better idea,” Smallcomb said.

Even then, a wet El Niño winter for California normally means a wet winter for Southern California—but not necessarily for the rest of the state, including Mammoth.

Mammoth Lakes is considered to be in the central part of the state, making forecasting for the local area particularly tricky.

“Inyo and Mono County are right on the dividing line,” Smallcomb said. “That makes it hard to forecast what kind of a winter you will get, even if Southern California is wet.

The dry years could well continue—and continue and continue—if the historical climate records are anything to go on.

“We have had 100 to 140 year ‘mega drought’ cycles several times in the past 1,000 years,” Smallcomb said. “We know this from studying tree rings from the Lake Tahoe and Tenaya Lake area. Yes, they have been punctuated by some wet winters—it’s not as if there have been 100 years of unrelenting drought—but the overall pattern for these mega droughts is to be extremely dry.”

The past three years have not just been dry, they have been warmer than average, with the past winter the warmest on record.

The year 2013, including the last winter, has been the driest and warmest of all.

The heat wreaks havoc with the snowpack, as the warmth keeps the snow level low, elevation wise, meaning less of it can be captured and stored in the snowpack, he said.

The snowpack stores water much like a large reservoir does, allowing humans to tap it slowly and as needed for use during the rest of the year.

But when more precipitation occurs as rain, the big storage tank springs a leak. The state’s massive water dispersion and storage system is not designed to handle the new pattern that favors more rain and less snow.

The drought is also likely to increase fire danger—but not necessarily for the reasons people might think.

“We have not necessarily seen an increase in the number of fire weather events, like low humidity and high winds, in the past three years,” he said. “What we are seeing is a big decrease in the moisture left in all of the fuel out there, including even the large, mature trees.”

Trees in Tahoe are dying, he said, and the drought appears to be the culprit.

“The U.S. Forest Service in Tahoe told me it was the worst snowpack they had seen in 40 years,” he said.

Firefighters call this “fuel moisture” and they regularly measure the amount of fuel within different sizes of trees, shrubs and other vegetation, then use the information to create fire prevention plans or fight existing fires.

Large trees take longer to lose moisture than small fuels, such as grass and shrubs, due to their size.

For the past several years, firefighters in the Eastern Sierra have said, in previous interviews, that the fuel moisture in local vegetation has been very low; so low that vegetation in May will burn more like vegetation in a typical late summer or fall would burn.

That trend has not changed this year.

The one spot of good news from Smallcomb—if you can call it that—is that the Mammoth area lies at a comparatively high elevation, relative to the rest of the state.

Tahoe and Truckee-area forests in the Northern Sierra, which received more precipitation than Mammoth this past winter, are mostly at lower elevations than Mammoth’s forests and they received more of their moisture as rain, he said, because lower elevations are warmer.

“Even if you might have received less precipitation than the Tahoe area, which you did last year, you got more snow than Tahoe,” Smallcomb said.

“That is the one big factor in your favor, in terms of snowpack.”

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