The study examined avalanche release mechanisms in a maritime snow climate to improve hazard assessment and prediction at Snoqualmie Pass. Hazard level and potential release times depend on weather conditions and snow stratigraphy in the starting zones of avalanche paths.
Most avalanches release less than one hour after the onset of rain and before liquid water or a thermal wave has penetrated more than a few centimeters into the snow. Prediction of the timing of these immediate avalanches requires observation systems that give advance notice of the onset of rain. New instrumentation installed at nearby mountain sites, with a telemetry link to Snoqualmie Pass, improved predictive capability.
In some conditions, avalanches can be delayed and the hazard can remain high for at least a day. Prediction of the timing of delayed avalanches is more difficult and requires information about the mechanical response of the snowpack to the penetration of liquid water and heat. A new method based on observation of strain-rate in the snow was developed to quantify the effects of changes of temperature and precipitation on the snow structure. This technique may prove useful for predicting avalanche release but requires additional research before it can be used operationally.
September 21, 2007
Howard Conway, Charles F. Raymond.
Washington State Transportation Center (TRAC)
- # of Pages: 191 p., 4,092 KB (PDF)
- Subject: Avalanches, Climate, Passes (Mountains), Roads, Roadside hazards, Snow, Snow and ice control, Snow phenomena, Telemetry, Weather, Weather forecasting.
- Keywords: Maritime climate, avalanche, wet snow, snow structure, liquid water, Snoqualmie Pass, I-90.
- Related Publications: Prediction of Snow Avalanches in Maritime Climates: Final Report, (WA-RD 203.1).
This abstract was last modified April 29, 2008