A relatively dry January in portions of the Columbia River basin have sent snowpack runoff forecasts for the spring and summer into a bit of a freefall, and started to raise concerns for fish managers, hydrosystem operators and other water users.

The Northwest River Forecast Center's initial water supply forecast for the basin, its Dec. 28 "early bird," estimated that the most probable outcome would be runoff at 101 percent of the 30-year average for the January to July period at The Dalles Dam in the lower Columbia. That measuring point includes water funneled from mountains in the Columbia 's northernmost reaches and from the Snake River basin .

The National Weather Service forecasters' final or "official" monthly forecast Jan. 7 pegged the most probably outcome at 98 percent and the mid-month forecast on Jan. 19 dropped to 96 percent. The NWRFC produces three statistical forecasts each month, adding in additional data as it becomes available for the official forecast.

The latest early bird, posted Thursday, drops The Dalles runoff forecast again, to 93 percent of average. It assumes precipitation at 80 percent of normal through Feb. 15 and normal precipitation for the balance of the winter-into-spring season.

Precipitation totals for the October through December period are near or above normal across much of the basin with the exception of southeast Oregon , where totals were from 90 to 70 percent of normal to less than 50 percent.

Precipitation totals were padded as a result of rain events early in the fall. The cold season, a time when water is stormed as snowpack that can be used through the next summer, has not been as blessed.

"It's quite a bit different picture when we're looking at snow. It's very light out there," the NWRFC's Steve King said during a Wednesday presentation to the Regional Forum's Technical Management Team. The TMT's federal, state and tribal participants help guide Columbia/Snake river hydrosystem operations with a goal of making salmon and steelhead migrations as easy as possible.

The National Resource Conservation Service's SNOTEL automated measuring sites show a few areas of strength. The snow-water equivalent in the snowpack feeding central Washington 's Yakima and Ahtanum basins was at 116 percent of normal through Wednesday. The Chelan, Entiat and Wenatchee snowpacks were at 114 percent and Washington tributaries feeding into the Columbia above the Methow River were at 110 percent of normal.

No other area monitored in the U.S. portion of the Columbia basin had an above average snowpack this week with the exception of the Lewis-Cowlitz in the lower river. British Columbia snowpacks in the basin were for the most part at or above average for this time of year.

But the Owyhee drainage in northern Nevada-southeast Oregon had snowpack with a snow-water equivalent at 54 percent of normal. South-central and southern Idaho snowpacks were at 70-65 percent of normal this week.

King said that snow conditions are extremely low in the upper Snake, but balanced somewhat by conditions in British Columbia and the northern Rockies , the source of about 30 percent each of the basin's runoff total on average.

Thursday's early bird pegged the most likely runoff scenario at northeastern Washingon's Grand Coulee Dam on the Columbia to be 99 percent of normal for the January-July period, about 62.1 million acre feet. That's down from a 102 percent forecast after a dry January.

The Feb. 1 forecast is for runoff past Lower Granite Dam to be 79 percent of normal or 27.7 MAF. That's down from a Dec. 28 forecast of 95 percent of normal runoff. Lower Granite is on the lower Snake River in southeast Washington and passes most of the water from that basin before feeding into the Columbia .

Precipitation totals in the New Year thus far have been 86 percent of average in the Upper Columbia, 36 percent in the Mid-Columbia, 32 percent in the Lower Snake and only 21 percent in the Mid and Upper Snake, according to information presented at the TMT meeting by fish and wildlife managers. And the near-term forecast is dry.

Given the falling runoff predictions and relatively Spartan precipitation forecasts, managers on Wednesday urged conservative use of water stored, and flowing into, Grand Coulee 's reservoir to assure flows downriver through the emergence of chum salmon fry from eggs.

The most recent forecasts from the National Weather Service's Climate Prediction Center are for an equal chance of above or below average precipitation through April across most of Oregon and Washington but below average precipitation for most of Idaho and northwest Montana .

King said that the fall-winter weather to-date has not appeared to follow a "typical El Nino" pattern, even though El Nino conditions have been evident in the equatorial Pacific since early last year. Those conditions general increase the chances that the Pacific Northwest will have a drier, warmer winter season and can affect weather around the globe.

The Climate Prediction Center in a Jan. 11 diagnostic discussion published online says most analytical models indicate that the El Nino conditions will decrease from February through May.

But, the CPC says, "there is an increased probability of observing El Niño-related effects over North America during January-March 2007, including warmer-than-average temperatures over western and central Canada , and over the northern United States , wetter-than-average conditions over portions of the U.S. Gulf Coast and Florida , and drier-than-average conditions in the Ohio Valley and in portions of the Pacific Northwest ."

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
NOTE: In accordance with Title 17 U.S.C. section 107, any copyrighted
material  herein is distributed without profit or payment to those who have
expressed  a  prior interest in receiving this information for non-profit
research and  educational purposes only. For more information go to:
http://www.law.cornell.edu/uscode/17/107.shtml

Source:  https://cbbulletin.com/Free/201654.aspx