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Snowpack is high, but moisture is evaporating

January 21, 2011

Sure we got a lot of snow. But with a very dry January, the snowpack is slipping quickly, making it still too early to celebrate. Photo/Wendilyn Grasseschi

Although the current snowpack on top of Mammoth Pass is at 297 percent of normal for the second week of January, it’s still too early to celebrate.

“If we don’t get any snow, and there’s none forecast, this could be the wettest December on record followed by the driest January,” said state snow surveyor John Dittli.

Despite the snowiest December on record, there’s still reason to keep at hand that snow dance routine most longtime Mammothites know.

So, if things continue as they are forecast, the wettest December might be followed by another record -and not a wanted one.

That fact alone isn’t that worrisome. After all, there’s another two months of winter still out there, when anything could happen.

But there’s something else going on this month that he’s never seen before so early in the year.

When Dittli was out at the Bishop-area Tablelands this week, he noticed something odd.

“The snow was literally evaporating right in front of me, it was so warm,” he said. “It was amazing, the air was full of moisture.”

The phenomenon, called “ablation” is defined by glaciologists as the melting of snow or ice by evaporation, with air temperature typically being its main cause.

Some of the Mammoth snowpack is, of course, headed to reservoirs via creeks and rivers and is trickling into the ground and replenishing groundwater supplies, all of which is a good thing.

But record high temperatures in the Owens Valley and very unseasonably warm temperatures here in the upper regions of the county are making that snowpack a bit shallower than most would have imagined a few short weeks ago.

It’s a trend that could spell problems down the road if things don’t change.

But Frank Gehrke, the state’s snow surveyor coordinator, isn’t too worried — yet. He said that although high temperatures play a part in lessening the snowpack, what’s really making a difference is the sheer number of sunny days in January. That has had an impact.

“Clearly, there is a loss,” he said.

And he too, noted that the warm temperatures were adding up.
“It’s been as warm as 45 and 50 degrees above nine, ten thousand feet,” he said. “There’s clearly a loss from that, but the sun is still so low in the sky, it’s not critical.”

But it’s too soon to get worried, he said. Most of the critical data comes from the snow surveys taken at the end of each winter month, with the January total due in a week or so. February, traditionally one of the Sierra’s wettest months, is the “big one” for people who make a living watching the Sierra snowpack.

“That’s when we will really have some data we can use,” he said.

Long range forecasts by the National Weather Service show no storms of any consequence, for at least the next week or two.

On the bright side, Mammoth’s weatherman Howard Sheckter notes a commonality of La Nina winters in recent posting on his web site.

“The Dweebs have said it before and they will say it again……La Nina winters are highlighted by intense stormy periods with long breaks in between.

“Winter will be back!”

Nevertheless, it might still be a good idea to review those snow dance steps.

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