Snowpack great for stream flows; some worry about rapid melt
The Associated Press
YAKIMA, Wash. -- The heavy snow pummeling Washington's Cascade Range is a headache for travelers, who saw two major highways temporarily closed Monday due to avalanches. Now the snow at lower elevations is raising concerns about the potential for record flooding in a quick thaw.
Snowpack statewide stood at 129 percent of average as of Feb. 1, according to data recorded by the Natural Resources Conservation Service. That figure increased to 139 percent of average by Feb. 8 after storms swept through the state in the first week of February.
That snow is unlikely to melt quickly, which bodes well for stream flows, fisheries and municipal and agricultural water supplies come summer, said Scott Pattee, Conservation Service water supply specialist. Reservoir capacity also was fairly normal.
Of greater concern, Pattee said, are the snowpack levels at lower elevations, which are more likely to thaw quickly and result in flooding.
There are 61 automated snowpack measurement sites in the state. Thirty-three sit below 4,500 feet, and 12 of those set new high water content records.
"If we did happen to have a change in these weather patterns ... it could put us in some peril for potential flooding, high water and runoff," Pattee said.
In 1996, when snowpack statewide was actually below average, a warm weather system that melted heavy snow at lower elevations resulted in significant flooding and hundreds of millions of dollars in damage. Two people died in the floods, and at least 21 counties and the Yakama Indian Reservation were declared disaster areas.
The Palouse River inundated the central business district of the town of Palouse, about 50 miles southeast of Spokane near the Idaho border. Flood waters damaged virtually every road in Columbia County and forced the closure of 25 of 29 county bridges.
West of the Cascades in Woodland, along Interstate 5 north of Portland, Ore., more than 2,000 people were evacuated at the height of the floods.
After the 1996 floods, water supply specialists installed a new water measurement site in Eastern Washington's hard-hit Asotin County, at a fairly low elevation, Pattee said. At the site this year: 3 feet of snow, with a water content of about 10.5 inches. Locals say the same site had no more than 2 feet of snow in 1996.
"They had fairly extensive flooding (in 1996) -- very torrential rains too, which was the big thing," Pattee said. "Even if it warmed up to 50 degrees and the snowpack came off fast, we probably wouldn't see extensive flooding. It's when you add all that hard rain."
Forecasters are calling for more of the same wet precipitation pattern that has been repeatedly dumping snow across the state and raising the avalanche danger. The bigger question is temperatures accompanying that precipitation, which are still uncertain.
On Monday, U.S. Highway 2 near the summit of Stevens Pass and eastbound Interstate 90 over Snoqualmie Pass were closed for several hours due to avalanches. Both had reopened by Monday evening.
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