Snowpack news: Lack of precipitation in March, warm temperatures and wind = statewide snowpack at 49% of the thirty year average

snowpackcolorado04052012.jpg

From the Summit County Citizens Voice (Bob Berwyn):

“March was the real game-changer,” [State Climatologist Nolan Doesken] said, explaining that the state’s snowpack usually grows and peaks during the last few weeks of winter; this year, it was the opposite, with a meltdown that saw statewide snowpack dwindle by nearly a third.

In fact, some parts of the central and northern mountains recorded above average precipitation in January and February, but that wasn’t enough to make up for a dry early winter, and when March turned balmy, the snow simply vanished.

“We don’t expect north-facing, high-elevation slopes to melt in March,” said Doesken by phone from Durango, where he was attending an annual water-users conference.

High-wind episodes during some of the dry periods between storms also were a factor, scouring the snow from some of the highest elevations, where the snow usually builds into thick, deep pillows that slowly melt during the spring. Some of the snow that’s blown around by the wind also simply sublimates into the atmosphere, Doesken said.

That means most of the snow ended up at mid-elevations, in many cases in the lodgepole pine belt, where the beetle-kill may also be a factor in the rapid melt-down. Instead of being shaded by thick evergreen branches, the snow on the ground was exposed to the early spring sun.

There’s still a slight chance that a big wet storm — like a 2003 mid-March deluge that ended the 2001-2002 drought — could make up some of this winter’s deficit, but those odds diminish with each passing week, he said. And the outlook for the next few months from NOAA’s Climate Prediction Center continues to trend toward the dry side, with better than average odds for warmer-than-average temperatures and below-average precipitation, he added…

Some weather experts have suggested that a dry winter can affect the monsoon because there’s not as much localized moisture available for evaporation and condensation. But overall, there doesn’t seem to be much statistical data to support that conclusion, Doesken said. “There’s an ever-so-slight bias toward more precipitation after a dry winter,” he said, explaining that one theory is that early heating in the Southwest helps develop the big desert heat low pressure system that becomes the pump for monsoon moisture.

Leave a Reply