5/18/2026
Weekly conditions update:
– After a warm week of rapid snowmelt, only 25% of this year’s peak snow water equivalent remains on the ground, compared to 54% on average. Cool temperatures over the weekend slowed melt at the stations near or above 8,000 ft that still hold snow.
– After reaching a seasonal peak Thursday, streamflow in gaged tributaries is receding as snowmelt rates slow. Streamflow at the Snake River at Flagg Ranch gage is now 63% of average for the date. Water temperatures remained below 52 °F at all recording stations throughout the week.
– Jackson Lake is 96% full. Outflow has remained near 1,300 cfs since last week. Reclamation expects additional increases early this week.
– Palisades outflow increased from 12,700 cfs to 14,000 cfs on May 14th. The reservoir is currently 41% full.
At last week’s public meeting, Reclamation said they are expecting all major reservoirs in the Upper Snake River system, including Jackson, to be heavily drawn down this summer. They expect high summer outflows around 3,000-5,000 cfs below Jackson. With low natural water supply and high storage water use expected across the basin, they indicated Jackson storage levels may be near or below 50,000 acre-feet by the end of the summer. If the drop in water levels track similar historic years, this could mean the Colter Bay boat ramp is inoperable by mid- to late-July.
Data are from NRCS SNOTEL, US Geological Survey, US Bureau of Reclamation, and the National Weather Service.