Avalanche Forecast
Issued: Jan 14th, 2015 8:04AM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs.
rbuhler,
Avalanche Canada
We have entered a low probability/high consequence period. Large and destructive human-triggered persistent slab avalanches remain possible.
Summary
Confidence
Fair - Timing, track, or intensity of incoming weather system is uncertain
Weather Forecast
The ridge of high pressure shifts into Alberta allowing a weak cold front to reach the interior Thursday overnight. Thursday should see a mix of sun and cloud up high with a layer of valley fog in most of the valleys. Alpine winds should remain light and freezing levels are expected to reach around 800m. Thursday night and Friday are forecast to receive 5-10mm of precipitation with moderate-to-strong SW alpine winds. Freezing levels are expected to be around 1000m or so. By Friday evening the system should be finished. Saturday is expected to see a mix of sun and cloud, freezing levels around 800m, light alpine winds, and the possibility of light flurries. Another weak system is expected for Sunday.
Avalanche Summary
No new avalanches have been reported since Saturday. On Saturday, a snowmobiler triggered a size 2 avalanche and was partially buried (YouTube video: https://www.youtube.com/watch?v=yhhAUcvXa3Q). This occurred in an opening at 1600m. It occurred on the mid-Dec weak layer down 40-50cm. Natural avalanche activity is not expected on Thursday. Skier triggering a persistent slab avalanche remains the main concern for the foreseeable future.
Snowpack Summary
The snow surface consists of widespread surface hoar up to 10mm, a sun crust on steep sun exposed slopes, a localized thin breakable temperature crust, and/or wind affected surfaces in the alpine. Recent warm temperatures have aided in the settlement of the week old storm snow. The persistent slab is typically 40-70cm thick and sits on the mid-December surface hoar/crust layer which remains sensitive to human triggering. The reactivity of this persistent weak layer appears to be quite variable but still has the potential for large, destructive avalanches in some areas. The layer appears to be the most reactive at and below treeline.
Problems
Persistent Slabs
A persistent weakness buried mid-December is spotty in distribution and reactivity, but remains problematic at and just below treeline where the snowpack structure may still be primed for human triggering.
Use conservative route selection, stick to moderate angled terrain with low consequence.>Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.>
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Jan 15th, 2015 2:00PM
