Posted: Thursday, May 10, 2012 11:00 AM
Water experts keep close eye on fluctuating temperatures
By DAN WHEAT
Snowpack in Washington's Cascade Mountains is 140 percent of average and while a major thaw is predicted, there should be plenty of irrigation water for farms through summer, the state's lead water supply expert says.
While a major thaw is normal, the one wild card that could upset the rosy scenario is temperatures, said Scott Pattee, water supply specialist for the Natural Resources Conservation Service in Mount Vernon.
"It's the one thing forecasters don't have a handle on yet. That's the unknown factor. If it spikes up and stays, it will bring the snow off faster," Pattee said.
The agency's May 1 Water Supply Outlook notes new record daytime high temperatures were set and lows stayed well above freezing in April at many SNOTEL automated snowpack and climate data collection sites.
The high temperatures and warm rain helped push most basins into melting. Snow surveys indicated snowpack densities in the 40 to 48 percent range, which means most sites "are on the verge of a major thaw," the report states.
SNOTEL sites at 6,000 feet elevation still received snow on May 3 but probably won't in the next storm, Pattee said. The freezing level will continue to move up and some high-level sites will hold onto snow into August, he said.
All irrigation systems are looking good for the season with good carryover, he said. Even some small reservoirs in the Okanogan have had to drain water to make room for anticipated mountain melt, he said.