Friday, March 23, 2007

Early melt dissolving mountain snowpack

Official end to normally wet winter period is April 1

Express Staff Writer

A skier carves a turn on Bald Mountain, above a series of exposed hillsides that have lost their snow during a recent spell of warm weather. Photo by Willy Cook

It doesn't take a snow scientist to realize that Big Wood Basin snowpacks are melting earlier than normal.

Everywhere you look throughout the Wood River Valley these days, hillsides show more brown than white. This is especially true on the warmer south-facing hillsides where snowfree areas extend clear to the top of ridges in many places.

The 2006-2007 winter, which according to the calendar ended Tuesday, March 20, was an especially dry and warm one.

So, where does this leave the Big Wood Basin's overall snowpack compared to the past 30-year average?

As of Thursday morning, the Big Wood Basin snowpack had shrunk to just 64 percent of average. This is down from a 71 percent of average measurement on Jan. 31, after a promising start to the winter during the months of November and December.

The National Resource Conservation District manages 83 snow telemetry sites throughout Idaho, including nine in the Big Wood Basin. The "snotel" sites are basically remote weather stations that provide automated data on precipitation, snow depth and temperature.

The snow-water equivalent, which measures the amount of water in the snowpack, was just 53 percent of average at the Hyndman snotel site—the lowest percentage in the Big Wood Basin—on March 22. The Hyndman site is set at an elevation of 7,440-feet in the Pioneer Mountains, southeast of Ketchum.

The snotel at Galena Summit, set at an elevation of 8,780-feet in the Boulder Mountains northwest of Ketchum, was the highest in the basin at 75 percent of average on March 22. Other snotel sites in the basin include Chocolate Gulch, Galena Lodge, Dollarhide Summit, Camas Creek Divide, Soldier Ranger Station, Vienna Mine, and Lost-Wood Divide.

The Panhandle Region in northern Idaho was the closest to normal on March 22 with a basin-wide measurement of 83 percent of average, although it recorded 91 percent of average on Jan. 31.

The Big Wood Basin's neighbor to the east, the Little Wood Basin, is in even worse condition, with a basin-wide snowpack measurement of just 51 percent of average on March 22, the second lowest in the state. Only the Owyhee Basin in extreme southwest Idaho is worse off, with a paltry 47 percent of average snowpack on March 22.

All this coincides with the pending close to the normally wet winter period, which runs from October 1 through April 1.

Based on National Weather Service predictions, the months of April, May and June look to be something of a mixed bag in terms of temperature and precipitation forecasts.

Forecast maps the agency has released indicate most of Idaho will likely experience above average temperatures during those months. Precipitation forecasts for the same time period are far less clear and indicate equal chances of above or below average rainfall.

"That means it could go either way," explained Idaho Department of Water Resources spokesman Bob McLaughlin on Thursday.

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