The Upper Snake River Basin had Idaho’s best snowpack through the end of December, but the system’s water managers still aren’t breathing easy due to their meager storage water supply and an outlook for continued dry weather into mid-January.

The Upper Snake started the new year with 102 percent of median snowpack, though other Idaho basins remain well below normal.

“The way the water year ended was September precipitation was 200 percent of normal in the Upper Snake. That helped,” said Ron Abramovich, Idaho water supply specialist with the Natural Resources Conservation Service. “Then the rest of fall — October, November and December — precipitation was 60-90 percent of normal.”

Throughout November and December, high pressure forced storms from Canada through Wyoming, east of the Continental Divide, Abramovich explained.

Though snowpack is just 68 percent of median in the Upper Snake’s low-elevation mountains, Abramovich said its headwaters in Wyoming were hit by the string of storms.

Other Idaho basins weren’t as lucky. Abramovich said snowpacks through Jan. 1 averaged 40 percent of normal in the Weiser Basin, 55 percent in the Boise Basin and 58 percent of normal in the Payette. The Bear River snowpack is 75 percent of normal, though Bear Lake is still 93 percent of average from strong 2011 runoff.

Idaho irrigators are relying on an ample snowpack to fill reservoirs after a mediocre 2013 winter and a dry summer exhausted storage. In the Upper Snake system, Jackson Lake and Palisades Reservoir have a combined storage of 28 percent of capacity, roughly half of average.

Lyle Swank, watermaster for the Upper Snake system, said his reservoirs have a half million acre feet less storage now than at this time last year and are at their lowest capacities since 2004-2005.

“Snow is less than last year at most of our Snowtel survey sites. We need to get some snow pretty soon I think,” Swank said.

At 8 percent full and 19 percent of average storage, Owyhee Reservoir is at its fourth lowest level since it was built in 1936.

Weather models show a high-pressure ridge building over Nevada, which should continue to force storms away from the Northwest. Abramovich knows of a forecaster who has predicted dry weather for the region through at least Jan. 21, based on conditions in the Bering Sea.

“If January continues dry like we’re looking at now, then we’re going to be playing catch-up for the rest of winter,” Abramovich said. “By Feb. 1, we’re 60 percent of the way through winter.”

Fortunately, he said the atmosphere has been extremely active, making long-term predictions challenging.

“This lower elevation snowpack that really helps us with natural flow in the early season and tops off our reservoirs, if we don’t get some of that it’s going to be a tight year without a doubt,” said Steve Howser, general manager of Aberdeen-Springfield Canal Co., which has Upper Snake storage.

Though Howser feels lucky relative to growers in southwestern Idaho, he emphasized, “Just because we have a little better snowpack at the end of December doesn’t mean we have a rosy outlook at all.”