Northwest Avalanche Bulletin

This information is issued by the NW Avalanche Center, a federal agency in Seattle, WA.

This advisory is no longer issued except for unusual conditions. There are some generic spring avalanche safety notes below, and you can learn more on our Spring and Summer Avalanche Hazards page in our Education Center.

Northwest Weather and Avalanche Center Advisory

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300 PM PDT FRI OCT 3 2008
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FALL AVALANCHE STATEMENT

As the winter season rapidly approaches, the Northwest Weather and Avalanche Center is preparing once again to provide daily avalanche forecasts for the Olympics and Cascades.

These forecasts will become available in late November or December when sufficient snow has accumulated at moderate and lower elevations to create a potential avalanche danger.

These forecasts to not apply to developed ski areas or highways.

For your information a few general notes regarding fall avalanches follow . . .

During the fall the atmosphere experiences significant cooling at higher latitudes. As this cold northern air is mixed progressively southward by fall storms, pronounced changes in the air temperatures over the Northwest are a characteristic result. These large temperature variations can result in rapid decreases in the snowpack stability in areas with sufficient snow to slide. Wet cool weather depositing substantial snowfall at the higher elevations followed by rapid warming still common in the fall can quickly produce greatly increased avalanche danger. In the fall this problem is usually confined to permanent snow fields on the volcanic peaks, as vegetation and other anchoring prevalent at lower elevations generally prevents slides of a shallow snow cover.

Back-country travelers should make terrain, weather and snowpack stability evaluations as they travel over snow covered terrain. Remember that seemingly insignificant slides may be dangerous. Almost half of all avalanche fatalities occur in slides traveling less than 300 feet.

Have a safe and enjoyable fall and winter!

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