Updated Jan. 25, 2019
We closely monitor snowpack during the winter. Snowpack serves as an important water supply because it feeds rivers and streams as it melts in the spring and summer.
After one of the slowest starts for snowpack in 30 years, a stormy December helped the snowpack bounce to near-normal levels statewide by the new year. Since then, warmer than normal temperatures have caused us give back some of those gains. With warmer than average conditions expected to persist into the spring, it’s unlikely, but not impossible, that the overall snowpack will achieve normal levels by April.
We will regularly post information on this webpage about snowpack and how conditions may affect water supply forecasts.
Snowpack & precipitation
Statewide mountain snowpack
is at 83 percent of normal as of Jan. 25. That’s about 12 percent less than we were at the end of 2018.
Snowpack levels vary and some of the state is normal or close to normal. Higher elevation areas in the North Cascades and the Upper Columbia basin are faring the best. The Upper Columbia area is currently at 100 percent of normal. The lowest is 64 percent of normal in Central Puget Sound. The South Puget Sound and Lower Columbia watersheds are also lagging.
Snoqualmie Pass averages 252 inches of snowfall by the end of January. As of last week, about 148 inches had fallen.
There is still a lot of winter remaining with a wide range of possible outcomes before the end of the snow season, which is usually around early April. These odds for recovery diminish the longer we remain below normal and the closer we get to April.
Since the beginning of the year, the Olympic Mountains and the interior Columbia Basin have received above normal precipitation. Southwest Washington and the Cascades are still experiencing longer term precipitation deficits.
The U.S. Drought Monitor
, a tool we use to assess water supply, indicates abnormally dry or moderate drought conditions over the southern tier of the state and over the Cascades. Most of Western Washington and portions of the interior Columbia Basin currently indicate the absence of dry conditions. The Drought Monitor relies on a variety of indicators — such as streamflows, soil moisture, and snowpack — to make its assessment.
2019 is off to a warm start. Temperatures for January have averaged 2-4 degrees above normal across the state, with the Columbia Basin experiencing even greater anomalies in the 5-6 degree range. As a general rule, freezing levels rise about 1,000 feet for every 3.6 degrees increase in temperature. Given that more area is located in lower elevations than higher elevation (visualize a pyramid), higher freezing levels can mean substantially less area with snow.
Equatorial sea surface temperatures are above average across most of the Pacific Ocean. The patterns of convection and winds are mostly near average over the tropical Pacific. El Niño is expected to form and continue through the Northern Hemisphere in spring 2019 (~65 percent chance).
The Climate Prediction Center forecasts warmer than normal conditions extending through April. There is a lack of strong signal with respect to precipitation, but odds are slightly higher for drier conditions along the southern tier of the state.
Rivers & streams
The seven-day average streamflow statewide shows mostly normal flows for rivers. The daily mean streamflow is below normal at 9 percent of measuring stations.