National Weather Service United States Department of Commerce

Quick Synopsis:


Mountain snowpack and associated snow water equivalents (SWEs) across central through northwestern Wyoming were generally above to much above average by the end of February; while SWEs across basins in southern Wyoming were generally below average.   SWEs at the peak snowmelt runoff elevations (8,500’ – 10,000’) were the highest across the Shoshone and Upper Yellowstone Basins at 160 to 170 percent of median.  The Lower Green and Little Snake Drainages had SWEs at 75 to near 85 percent of median at the peak snowmelt runoff elevations.

This outlook is based on various diverse hydrological factors such as snow water equivalents (SWEs) in the mountain snowpack,
basin morphology (i.e. how basins respond to snowmelt runoff),  antecedent soil moisture, biological factors
(bark beetle kill/spruce blight), low elevation snow depths, and likely temperature and precipitation trends during late spring/early




Moderate to High potential for flooding associated with snowmelt runoff is expected across extreme lower portions of the Big Wind Watershed and over upper sections of the South Fork of the Shoshone Watershed…

 …Moderate potential for snowmelt runoff flooding is forecasted across the middle to lower portions of the North/South Forks of the Shoshone Basin, middle to lower sections of the Little and Big Wind Watersheds, and along headwater creeks and streams along the west side of the Big Horn Mountains...

…All other of headwater basins across Wyoming can expect a generally Low potential for flooding due to springtime snowmelt runoff...



Other hydrological information for Wyoming can be found at the NOAA hydrology website:

Monthly Wyoming Hydrologic Summary and Graphics:

(updated monthly around the 15th of every month)

Wyoming Drought Information Page:

(updated at least once a month)

Wyoming Graphical Water Supply Outlook:

(updated by the 10th of every month—January-June)

Wyoming Average Precipitation by Basin:

 (updated monthly)

Wyoming Spring Snowmelt Runoff Flood Potential Graphic:

(updated around the 25th of the month---February-May)

Current and Forecast Wyoming Streamflows and/or River Stages:


The current Wyoming Spring 2018 Snowmelt Runoff Flood Potential Outlook graphic: