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Archived

Avalanche Forecast

Mar 24th, 2017–Mar 25th, 2017
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
1: Low
The avalanche danger rating below treeline will be low

Regions: Glacier.

Careful decision making is still required with lingering persistent weak layers. With snow in the forecast, expect avalanche hazard to increase.

Weather Forecast

A cold front arrivers later this morning with up to 20cm of new precipitation for the area by Saturday evening.  Freezing levels rise to 1700m today, meaning a mix of rain and snow at lower elevations.  Winds will be light from the SW with occasional gusts to 40km/h.  Weather remains unsettled into next week with periods of sun mixed with flurries.

Snowpack Summary

Recently formed wind slabs exists on lee features above treeline with 10-20cm of soft powder in sheltered areas. Below 2000m, the upper 20cm is moist in the afternoon. Storm instabilities down 30-60cm are present but becoming less reactive. Persistent layers exists down 150cm (February crust) and near the base of the snowpack (November crust).

Avalanche Summary

2 size 2.5 avalanches were observed from the highway corridor on the north face of Mt MacDonald. These slides were triggered during a spike in wind speed late in the day on March 22nd. There have been reports of cornices failing and triggering large slabs in steep terrain in areas near Glacier National Park.

Confidence

Intensity of incoming weather systems is uncertain

Avalanche Problems

Wind Slabs

Recent winds overnight have formed isolated wind slabs on lee features above treeline. Wind slabs may be poorly bonded to last week's storm snow and may step down to deeper layers if triggered.
Use caution in lee areas. Recent wind loading has created wind slabs.Watch for shooting cracks or stiffer feeling snow. Avoid areas that appear wind loaded.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1 - 3

Persistent Slabs

The month of March has been characterized by heavy loading of new snow and rain.  After an intense avalanche cycle, the snow pack is still stabilizing. Deep weak layers have been failing sporadically leading to large avalanches.
Choose regroup spots that are out of avalanche terrain.Pay attention to overhead hazards like cornices which could easily trigger the deep persistent slab.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible

Expected Size: 3 - 4