Olympic Mountains’ snowpack well-fed

Snowpack in the Olympic Mountains and the rest of the state flourished amid a La Nina pattern in February, a water supply expert said.

A series of late-winter storms, including one that reached the North Olympic Peninsula lowlands, drove the snow water equivalent to 129 percent of normal in the Olympic Mountains at the end of last month.

“You’re definitely in good shape,” said Scott Pattee, a water supply specialist with the U.S. Department of Agriculture’s Natural Resources Conservation Service in Mount Vernon.

Olympic National Park reported 108 inches of snow at Hurricane Ridge on March 4.

A USDA map depicting snow water equivalents showed the Olympic Mountains at 169 percent of normal as of March 4, tops among 11 Washington basins.

That figure is skewed, however, because two of the three snow telemetry (SNOTEL) sensors that produce 30-year basin averages have been offline this week, Pattee said.

Pattee’s 129-percent number was taken from six sources — three SNOTEL sites and three snow courses, or manual field snowpack measurements at Hurricane Ridge, Cox Valley and Deer Park.

“With everything tied up in a nice bow, we’re looking at 129 (percent),” Pattee said in an interview last week.

“We can do a pretty good job of estimating what the snow water content is at those sites that haven’t been reporting just by using historic data and surrounding sites. We were able to do that for those two.”

The two non-reporting SNOTEL sites were the 5,010-foot Waterhole sensor near Hurricane Ridge and the 3,960-foot station at Mount Crag in east Jefferson County.

“Both of those sites are very remote, and so the only way to get into them is either by helicopter or by cross-country ski,” Pattee said in a telephone interview.

“Next week, I think we’re going to be able to get crews into Waterhole, and maybe try to get into Mount Crag.”

The one site that was producing a 30-year average — the 4,010-foot Dungeness site — had a 169-percent snowpack Thursday.

Normal is defined as the median snowpack from 1981-2010.

Snowpack provides a reservoir of meltwater for municipal water supplies, irrigation, fire suppression, recreation and fish habitat in the dry summer and early fall. It is a measure of water content in the snow, not the depth of the snow.

Cascade basin snowpacks, which feed hydroelectric dams that power the North Olympic Peninsula, also were well above average Thursday, according to the USDA map.

The Pacific Northwest is in a La Nina year. La Ninas are associated with colder-than-normal water temperatures in the eastern tropical Pacific Ocean and typically bring cool and wet weather to the region.

Snowpack on April 1 is a benchmark used to make predictions about water supplies because it is the historical peak of the snow season in the Olympics and Cascades.

Cliff Mass, University of Washington atmospheric sciences professor and Pacific Northwest weather guru, posted a blog on March 2 saying an above-normal April 1 snowpack was “pretty much guaranteed” given the current snowpack and extended forecast for March.

“All in all, very good news,” Mass wrote.