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Crazy Snow In Some Places Still Leads To Normal Water Supply Forecast For Basin
Posted on Friday, March 08, 2019 (PST)

A February wave of cold and snow, breaking records in some places, gave the water supply outlook a striking boost through much of the Columbia Basin, but all places were not equal.


As a result, the April-September forecast has not changed significantly for flows at The Dalles Dam, the final chokepoint for basin-wide runoff, said Ryan Lucas of the Northwest River Forecast Center in Portland during a teleconference on Thursday.


Still, Lucas pointed out how basin-wide fortunes have changed since the end of January, when lagging snowpack, warmer-than-average temperatures and below-average precipitation prevailed.


“You can see in the Upper Columbia, it was much colder than it was during the first months of winter … The southern two thirds of our basin really saw some significant precipitation, with records set in some places,” Lucas said.


Now the basin is “looking closer-to-normal or above-normal precipitation,” he added, specifically citing central and southern Oregon’s previously parched Cascade range, and the entire Snake River Basin.


Snake River basins now have April-September water supply forecasts ranging from 66 to 140 percent of average, while Columbia River Basins above Grand Coulee Dam have forecasts of 79 to 107 percent of average and the west side of the Cascades are at 81 to 94 percent of average.


Graphically, this represents a big turnaround from conditions that were present at the end of January, Lucas said. However, extremely cold temperatures produced a lot of light snow with less snow water equivalents in some areas.


April through September water supplies as of March 6, compared to Feb. 5 on a 30-year average, break down like this:


Upper Columbia River at Grand Coulee Dam are at 87 percent compared to 89 percent; Upper Snake River basins are at 103 percent compared to 84 percent; Middle Snake Tributaries are at 103 percent compared to 67 percent.


The resulting balance for the Columbia River at The Dalles Dam is 87 percent of average as of March 6, compared to 87 percent as of Feb. 5.


The April-Sept. water supply forecasts for the west Cascades are lowest from the northernmost on the Skagit River near Concrete at 84 percent of average to the highest at the southernmost Rogue River, which as at 113 percent of average.


Temperatures swings throughout the basin over the last month have been striking. Temperature departures in the Columbia Basin above The Dalles averaged out at nearly 10 degrees below normal. That’s compared to a departure of 4 degrees above normal at the end of January.


Lucas said there has been significant cold and snow at lower elevations, which can be more difficult to monitor aside from established weather stations in towns and cities. Record cold and snow were recorded for February in many of those locations.


Bend, Ore., received nearly 46 inches of snow in February, almost doubling a record that has stood for more than a century. It was also the third coldest February on record for Bend.


Coeur d’ Alene, Idaho, experienced the longest cold spell on record, punctuated by a low of minus 2 degrees — the first below-zero temperature dating back to December of 2016. As of early this week, the city had received just over 56 inches of snow, and any snowfall that would exceed 57.8 inches over the next few weeks would exceed a February-March record for snowfall set in 1955.


The National Weather Service in Missoula reported that February was the snowiest ever in Kalispell, Mont., with just over 33 inches recorded. And, it was the second coldest February on record for Kalispell, with an average 12.6 degrees. The record of 4.9 degrees was set in 1936.


And Seattle marked its year of “Snowmaggedon,” the snowiest winter in 50 years as of the end of February, with 20.2 inches, shattering the record of 13.1 inches set in 1949. February of 2019 was also the third coldest on record for Seattle with an average temperature of 36.7 degrees.


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