SUMMER AVALANCHE STATEMENT

Please note that the Northwest Weather and Avalanche Center is closed for the summer.  However, daily operation is scheduled to begin again in the fall.

Because avalanches continue to occur at higher elevations during the summer months in areas having either residual snow cover or permanent snow and ice cover, and several people within the Northwest have been killed by these events, here are a few notes about summer avalanches.

Avalanches occurring during the summertime can be generally grouped into three types:

First, wet slides within the existing snowpack are similar to wet spring slides, as progressive weakening occurs within the snowpack through melting and water percolation.  Although these slides are most likely to occur during the warmest part of the day, they may occur at anytime of the day during periods when the snowpack does not refreeze substantially at night.

The second type of summer avalanche occurrence is associated with new snowfall at high elevations.  Summer snowfalls are usually followed by substantial warming of the newly fallen snow as air temperatures rise rapidly with intense summer sunshine.  When the new snow overlies an old snow, ice or smooth rock surface this may lead to possible wet loose or wet slab avalanches.

The third type of summer avalanche is an ice or snow and ice avalanche.  These are usually triggered by the failure of large ice blocks such as seracs within glacier icefalls.  This in turn may involve additional ice and/or snow.  Timing of these events are mostly random, usually being associated with both meteorological conditions and glacier motion.  However, they are most likely to occur during extended periods of warm weather.

Climbers, hikers and other back-country travelers during the summer are advised to evaluate snow stability and use normal safety practices for travel in avalanche terrain with snow cover.

If you have any comments or suggestions regarding this past season's mountain weather or back‑country avalanche forecasting program, please direct them to:

Northwest Weather and Avalanche Center

7600 Sandpoint Way NE

Seattle, WA  98115

 

Or you may email comments to:

nwac.sew@noaa.gov

 

Have a safe and enjoyable summer!

 

Moore/Northwest Weather and Avalanche Center