Wyoming Water Supply Outlook--May 8, 2020

Back-to-Back Pacific Storms to Impact the West Coast; Heavy Snow in the Central Appalachians

Back-to-back powerful Pacific storm systems to impact the Pacific Northwest and northern California through the end of this week with heavy rain, flooding, strong winds, and higher elevation mountain snow. A strong, long-duration atmospheric river will accompany the Pacific storms, bringing excessive rainfall and flash flooding to southwest Oregon and northwest California through the week. Read More >

HIGHLIGHTS:

…Wyoming April 2020 precipitation was 75 to 85 percent of average...

...Current water year precipitation is averaging 90 to 100 percent of normal across Wyoming…

…Early May mountain snowpack across Wyoming is 85 to 95 percent of median...

…Near normal (90 to 105 percent) snowmelt streamflow volumes are still expected across several major basins in Wyoming…

…Wyoming reservoirs continue to average 75 to 85 percent of capacity in early May…

SYNOPSIS:

April 2020 precipitation totals across Wyoming were 75 to 85 percent of average. Precipitation numbers varied between 135 percent of normal over the Snake River Basin (far western Wyoming) to 60 to 65 percent of average over the Powder and Belle Fourche Drainages (northeastern Wyoming). Current water year (October 2019 - April 2020) precipitation across Wyoming was 90 to 100 percent of average.

Mountain snowpack across Wyoming was 85 to 95 percent of median by early May. Snowpack "water" numbers and/or SWEs were the highest across basins in northwestern Wyoming—varying between 105 to 115 percent of median. SWEs across basins in south central through southwestern Wyoming (Sweetwater, Upper Bear, and Lower Green Basins) were below 85 percent of median.

Near normal (95 to 105 percent) snowmelt streamflow volumes are still expected across several major basins in Wyoming. Above average snowmelt streamflow volumes are expected across portions of the Laramie, Upper North Platte, Shoshone, and Snake River Watersheds. The Sweetwater and Upper Green Basins as well as portions of the Little Wind River Drainage are still forecasted to have below normal streamflow volumes during the upcoming snowmelt season.

Wyoming reservoirs are averaging 75 to 85 percent of capacity in early May. Reservoir storages across Wyoming remained above average at 105 to 115 percent for May.

The Wyoming Water Supply Graphic: