Avalanche Forecast
Regions: South Columbia.
Above freezing temperatures up high over night and into the day Thursday will continue to stress the snowpack. Consecutive hot days are increasing the likelihood of triggering large avalanches on a crust near the bottom of the snowpack.
Confidence
Low - Uncertainty is due to the limited number of field observations.
Weather Forecast
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WEDNESDAY NIGHT: Clear / Light, southwest ridgetop wind / alpine low temperature +4 / Strong temperature inversion with above freezing air 2000-3500 m.
THURSDAY: Mix of sun and cloud / Light, southwest ridgetop wind / alpine high temperature +4 in AM with dropping temps in PM / Strong temperature inversion with above freezing air 2000-3500 m will dissipate in PM.
FRIDAY: Mostly sunny / Moderate, southwest ridgetop wind / alpine high temperature -2 / Freezing level 700 m.
SATURDAY: Sunny / Moderate, southwest ridgetop wind / alpine high temperature +6 / Strong temperature inversion returns with above freezing air 2000-3500 m.
Avalanche Summary
The hot weather up high has the potential to awaken the November crust and make it more sensitive to natural and human triggers which could result in large avalanches.
Data is very sparse in this region. Please submit your observations to the Mountain Information Network!
Snowpack Summary
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A very strong temperature inversion has created moist snow on all aspects at treeline and above on Wednesday. 10 cm of snow on Monday covered a new layer of surface hoar. Last week’s strong southwest winds created wind slabs that are still lingering on lee features at treeline and above. These wind slabs may be surprisingly reactive in areas where they are sitting on a layer of small surface hoar. There are a couple of crusts in the mid snowpack, from mid and early November. The most prominent of these is from early November, and it has been reported that there are weak, sugary facets above and below this crust. It is down approximately 70-100 cm, and is most likely to be reactive to human triggers on south facing slopes and in shallow, rocky, snowpack areas in the alpine.
Terrain and Travel
- Avoid exposure to overhead hazards when solar radiation is strong.
- Back off slopes as the surface becomes moist or wet with rising temperatures.
- If triggered loose wet avalanches may step down to deeper layers resulting in larger avalanches.
- Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
- Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
Avalanche Problems
Loose Wet
Things are looking HOT up high for the next couple days. Naturally triggered wet loose avalanches are possible on all aspects and especially likely on solar aspects. Overhead hazards will be a primary concern.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Likely
Expected Size: 1 - 1.5
Deep Persistent Slabs
The hot weather up high over the next couple days may awaken this layer. Cornice falls, or smaller avalanches are especially likely to trigger a large avalanche on this layer. This layer is most likely to be reactive to human triggers on south facing slopes and in shallow, rocky, snowpack areas in the alpine.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Possible
Expected Size: 2 - 2.5
Wind Slabs
10 cm of new snow and moderate northwest winds on Monday formed small wind slabs on lee features at treeline and above.
Aspects: North, North East, East, South East, South.
Elevations: Alpine, Treeline.
Likelihood: Possible
Expected Size: 1 - 1.5