In the Northwest United States, warming temperatures threaten mountain snowpacks. Reliable projections of snowfall changes are therefore critical to anticipate the timeline of change. However, producing such projections is challenging, as most state‐of‐the‐art climate models are limited in sufficiently resolving influential topography. Here we leverage atmospheric freezing level to estimate precipitation phase and project twenty‐first‐century snowfall frequency change at Snowpack Telemetry Network stations across the Northwest. Under “moderate” and “business‐as‐usual” emission pathways in Coupled Model Intercomparison Project phase 5 models, snowfall frequency is projected to decline at all stations. Business‐as‐usual declines accelerate after midcentury at most locations, whereas moderate declines decelerate. A “critical year” analysis identifies when decadal‐mean snowfall frequency is projected to fall below 50%, 25%, and 10% of cold‐season wet days. Results highlight regions particularly vulnerable to relatively near‐term change, such as the Cascade Range. Considerable station‐to‐station spatial variability emphasizes the value of this site‐specific approach