All wet in West

The Daily Inter Lake

Above-average precipitation in valley hasn't affected snowpack depths

April showers are doing their part to replenish local aquifers, but they don't seem to be having much effect on Northwest Montana's mountain snowpack.

Since April 1, almost an inch of rain has fallen at Glacier Park International Airport as of noon Thursday.

That raised the year-to-date total to more than 5 inches of precipitation, and more than 9 inches since the current water year began Oct. 1.

Given above-average precipitation in four of the past six months, the valley is running more than 25 percent above average for the year, and more than 10 percent above average since Oct. 1.

However, the April showers haven't translated to deeper snowpacks in Northwest Montana, according to data from the Western Regional Climate Center and the Natural Resources and Conservation Service.

Only a couple of the automated snow stations throughout the region have recorded significant increases in snow depth or snow-water equivalent during the last week. Snow-water equivalent is used to measure how much water is contained in the snowpack.

The Noisy Basin station in the South Fork drainage, for example, recorded a 9 percent increase in snow-water equivalent since March 31, from 44.8 inches to 49 inches.

The Moss Peak station in the Swan Range east of Polson recorded an 11 percent increase during that same time, from 38.7 inches to 42.9 inches.

Most other stations, though, have either stayed level or dropped slightly in the past week.

Not that they're experiencing a huge deficit: The Western Regional Climate Center indicates that the snowpack at or above average in almost every river basin in Montana, except for a handful of basins near the Wyoming border.

The Kootenai River basin, for example, is running at 106 percent of average - a dramatic improvement over the record-low 53 percent of average it was at a year ago.

The Flathead River basin is currently 101 percent of normal, compared to 57 percent last year at this time.

The automated snow site on Flattop Mountain in Glacier National Park was reporting more than 10 feet of snow as of Thursday, with a snow-water equivalent of 47.2 inches.

The mountain snowpack is one of the major variables that determines when Going-to-the-Sun Road can open over Logan Pass.

Researchers at the Northern Rockies Science Center have developed a mathematical formula that predicts the opening date for the pass, based on the snow depth at Flattop Mountain on April 1.

During the past several years, the formula typically has been accurate to within a few days of the actual opening date.

Based on this year's snowpack, the predicted opening date is June 9.

However, weather conditions in April and May are even more important in determining when Sun Road can be opened fully. Frequent spring storms and abundant snowfall increase the avalanche danger, making it difficult for park employees to plow the road.