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Archived

Avalanche Forecast

Nov 23rd, 2020–Nov 24th, 2020
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
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
4: High
The avalanche danger rating in the alpine will be high
Treeline
4: High
The avalanche danger rating at treeline will be high
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable

Regions: Glacier.

A conservative approach to terrain selection remains key to managing the persistent avalanche problem.

Weather Forecast

An Aleutian Low is pushing weather systems our way, culminating with the passage of a cold front late Tuesday.

Today: Mostly cloudy with flurries. Alpine High -7 C. Ridge wind (RW) light SW. Freezing level (FzL) 1100m.

Tonight: Flurries (2cm). Low -8. RW moderate SW.

Tuesday: Snow, heaviest in the evening (15-25cm). High -6. RW Strong SW. FzL 1200m.

Snowpack Summary

Southerly winds in the high alpine have built fresh slabs in immediate lees. The Nov 5th crust is now buried over 1m in most starting zones. This crust complex is over 8cm thick, and can be found up to 2500m on all aspects; with facets above and below this is an active weak layer that will persist for a long time.

Avalanche Summary

No fresh avalanches observed since early Saturday morning.

Large natural avalanches were triggered by last weeks snowfall in the highway corridor. Several of these failed on the Nov 5th crust/facet layer.

There are several Min reports of natural, and skier triggered avalanches that occurred during last weeks storm.

Confidence

Timing, track, or intensity of incoming weather system is uncertain

Avalanche Problems

Persistent Slabs

Steep planar slopes should be avoided, especially at and just above treeline.

Recent natural and skier triggered avalanches, snowpack tests, and reports of whumphing, all indicate that this layer may still be triggered by the weight of a skier.

  • Avoid shallow snowpack areas where triggering is more likely.
  • Be aware of the potential for wide propagations which could result in large avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible

Expected Size: 2 - 3.5

Wind Slabs

Winds have mostly been in the light range, but with lots of snow available for transport the high alpine and wind prone areas like the Bonney morraines developed isolated fresh windslabs yesterday.

  • Use caution in lee areas. Recent wind loading have created wind slabs.

Aspects: North, North East, East, South East, North West.

Elevations: Alpine.

Likelihood: Possible

Expected Size: 1 - 1.5