West Slopes South - South of I-90 to Columbia River
The Northwest Avalanche Center has ended daily mountain weather and avalanche forecasting for the 2017-2018 season. Please see our spring schedule for more information about our forecast products for the remainder of Spring 2018.
Although daily forecasts have ended for the year, avalanche hazards will exist in the mountains. Travelers need specific skills to evaluate weather data, snowpack conditions, and avalanche terrain to make decisions about when, where, and how to travel in the mountains. It is not uncommon for avalanche fatalities to occur in the springtime.
The mountain snowpack is transitioning from winter to spring. This transition takes time. During stormy periods, expect wind and storm slabs to form at elevations receiving new snow. Key signs such as 12” of snow in 24 hrs, snowfall rates of 1”/hr, blowing snow, fresh cornices, and uneven snow surfaces with cracking all indicate that wind/storm slabs have likely formed. Stay off slopes greater than 35 degrees if you believe these conditions have developed.
Following fresh snowfall, the strong spring sun can rapidly increase the avalanche hazard! Wet avalanche conditions can develop very quickly with spring warmth and sunshine. New rollerballs, fan-shaped avalanche debris, and wet surface snow deeper than your ankle signify loose wet avalanches are becoming likely on similar slopes. Avoid steep slopes if you see these conditions.
During periods of fair spring weather, the avalanche danger is generally lowest during the night and early morning hours when the surface snow refreezes. Wet loose avalanche activity generally starts on east facing slopes receiving morning sunshine and progresses to the west facing slopes during the afternoon. Expect a poor refreeze and rapid increase in wet snow conditions following cloudy and mild nights. Plan your travel routes accordingly to minimize your exposure to wet snow hazards.
Other spring hazards:
Cornices have grown large over the winter. As temperatures rise they will begin to droop and fail, often without warning. Cornice failure can trigger larger avalanches on slopes below.
Glide cracks will form on steep smooth slopes as water reaches the ground. Glide avalanches may occur on these slopes. The exact timing of these events is very difficult to predict.
Creeks will open and snow bridges will weaken. Fatalities involving open creek holes or collapsed snow bridges occur nearly every spring.
Use caution if you plan to travel near or below any of these hazards. Employ appropriate travel routes and techniques to limit your exposure to cornices, glide avalanches, and creek crossings.
Consider the consequences of the terrain as you travel. Would an avalanche carry me off a cliff or into a gully? If so, would a different route be safer? Backcountry travelers need to be aware of both the terrain above and below intended routes in every season.