Snowpack & runoff

Glossary

Snow-water equivalent (SWE)

The depth of water you'd get if the snow melted right now. Basin figures are an average across the reporting stations in that basin.

% of normal

Current basin SWE compared to the long-term norm. 100% is right on the historical curve; 70% means the basin is carrying 30% less snow water than a typical year for this time of year.

Water year

October 1 through September 30. WY2026 runs Oct 1 2025 – Sep 30 2026. Aligns with how snow accumulates and runs off, not the calendar year.

Melt-out date

The typical date a basin finishes melting in a normal year. A late melt-out means runoff drags later and summer flows hold up longer.

Runoff forecast

Projected seasonal streamflow volume at a specific point, issued monthly January–June. Expressed as % of the long-term average for that period.