Water supply forecast released
Last updated 2/21/2023 at 12:23pm
SPOKANE – Forecasts from the Natural Resources Conservation Service shows a probability for above-normal precipitation and temperatures across Washington.
This annual report opens with a general outlook, indicating among other things that much of Washington remains in a "D0" status, which is abnormally dry, except for the Spokane area.
Spokane river basin snowpack was measured at 133% of the median, compared with last year's 105%.
Precipitation charts for December show Spokane county at 120% of average, compared with the water-year percent of average of 95%.
Automated "SNOTEL" climate sensors across Washington measure all forms of precipitation including, rain, snow, sleet, and hail.
Reservoir measurements indicated reservoir storage in the Spokane Basin were 32% of capacity and 109% of storage median.
The Yakima Basin was 344,600-acre feet, which is 92% of median for the Upper Reaches and 101% of median for Rimrock and Bumping Lakes.
The report indicates that the power generation reservoirs measured at Coeur d'Alene Lake, 76,900-acre feet, which is 109% of median and 32% of capacity; and Ross Lake within the Skagit River Basin at 64% of average and 85% of capacity.
Regarding streamflow, the report said, "Early winter forecasts for April-September stream flows are never quite as robust as they are later in the season when we know more about the winter climatology."
Spokane's percent of average forecast is between 95-106, with a 50% chance of exceeding that prediction, while the percentage of average December runoff is 62%.
The National Weather Service seasonal temperature outlook for Washington for Jan-Feb-Mar is likely below normal, while forecasts for precipitation remain at 33-40% probability of being above-normal.
The report maintains that forecasts of any kind "of course, are not perfect," and cites several factors which influence the accuracy of predictions.