Avalanche Forecast
Issued: Nov 23rd, 2020 8:05AM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs and Wind Slabs.
Jonas Hoke,
A conservative approach to terrain selection remains key to managing the persistent avalanche problem.
Summary
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
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
Expected Size
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
Expected Size
Valid until: Nov 24th, 2020 8:00AM
