Avalanche Forecast Glacier National Park

Friday 25th January 2019

Avalanche Danger Ratings Fri 25th Jan 8:00AM Danger Ratings Alpine: Considerable Danger Ratings Treeline: Moderate Danger Ratings Below Treeline: Moderate Wind Slabs Wind Slabs Persistent Slabs Persistent Slabs

Parks Canada Forecaster: andrew jones

Date Issued:

Valid Until:

Reactive wind slabs and a persistent weak layer require careful assessment and thoughtful decision making today.

Weather Forecast

Cloudy with sunny periods and isolated flurries for today. Trace amounts of precipitation, alpine temperature of -8.0, freezing level rises to 1000m and ridge winds west 20-35 km/h. Freezing levels are expected to rise Saturday with an alpine temperature of zero.

Snowpack Summary

Most open terrain in the alpine has been wind affected. In specific locations, strong S winds have redistributed storm snow and created loaded pockets and wind slabs on lee and cross-loaded features at treeline and above. The Jan 17 persistent weak layer down 30cm is surface hoar in sheltered areas and sun crust on solar aspects.

Avalanche Summary

A field team on Macdonald West Shoulder was able to skier control a size 1.0 avalanche on the Jan 17 crust/ surface hoar layer. The team also observed a natural size 2.0 avalanche in the start zone of Macdonald West Shoulder 1. A Na size 2.0 was reported from the S face of Ursus Major Mtn. Limited visibility in the highway corridor yesterday.

Confidence

Wind Slabs Wind Slabs

Likelihood

Likely

Expected Size

1 - 2.5

Strong S winds have created windslabs at treeline and above. These slabs have been easily triggered by skier loads in steep unsupported terrain. When triggered in certain areas, wind slabs may propagate into large avalanches.

Watch for shooting cracks or stiffer feeling snow. Avoid areas that appear wind loaded.Stay well to the windward side of corniced ridges.

Aspects: All aspects.

Elevations: Alpine, Treeline.

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Persistent Slabs Persistent Slabs

Likelihood

Likely - Possible

Expected Size

1 - 2

The Jan 17th layer is down 20-40cm and consists of surface hoar in sheltered areas and sun crust on steep solar aspects. This layer seems more problematic between 1600-2100m. Where soft slab exists, human triggered avalanches are possible.

Dig down to find and test weak layers before committing to a line.Use caution on open slopes and convex rolls where buried surface hoar may be preserved.

Aspects: All aspects.

Elevations: All elevations.

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