Avalanche Forecast
Issued: Feb 12th, 2022 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs, Cornices and Loose Wet.
rbuhler,
Avalanche Canada
Warm and sunny conditions continue to keep the danger elevated. Weak cornices and loose wet avalanches should be expected during the heat of the afternoon.
The biggest concern remains a weak layer down 30-70 cm which is capable of producing very large and destructive avalanches.
Summary
Confidence
Weather Forecast
One more day of very warm and sunny conditions before the ridge breaks down Sunday night. A weak system is forecast to bring light snowfall Monday morning.
Saturday night: Clear, light W wind, freezing levels around 3000 m.
Sunday: Mainly sunny, light SW wind, freezing levels 2500-3000 m.
Monday: Light snow in the morning, sunny breaks in the afternoon, light NW wind, freezing levels 800-1400 m.
Tuesday: Mainly sunny, light NW wind, freezing levels reaching around 1200 m.
Avalanche Summary
On Friday, a few natural cornice releases were reported, some of which triggered small slabs on the slopes below. One of the largest did not trigger a slab but ran 400 m. Some natural loose wet avalanches were also reported from steep sun-exposed slopes. In the northwest of the region, explosives triggered three moist storm slabs 10-40 cm thick on solar aspects and two cornices which triggered small slabs on the slopes below. Further south, explosives triggered wind slabs up to size 2 failing down 60 cm.
Last weekend, several very large human-triggered avalanches occurred on the late-January persistent weak layer. This layer is now sitting dormant but there is serious concern that it is going to wake up with sun and very warm temperatures this weekend. The layer is down 30-70 cm so it is still in the prime depth for human-triggering. Cornice releases are also a major concern for triggering persistent slabs so give extra caution to overhead slopes which are exposed to cornices.
Snowpack Summary
A widespread surface crust was reported on Friday which appears to have broken down a bit on steep sun-exposed slopes during the afternoon and reformed overnight with clear skies. Prior to the warming and sun, strong winds had caused extensive wind effect and wind slab formation in exposed terrain at higher elevations.
The problematic late-January crust/facet interface is now buried down 30 to 70 cm. This layer is most reactive between 1700 m and 2000 m, but is present above and below this elevation band and may still be reactive. It had produced several human and remote triggered avalanches last weekend. Although this layer is widespread, its exact composition and reactivity has significant spatial variability. In sheltered terrain at treeline and just above, surface hoar may sit on the crust which has the potential to further increase the reactivity of this interface.
Terrain and Travel
- Be aware of the potential for large avalanches due to the presence of buried weak layers.
- Remote triggering is a concern, watch out for adjacent and overhead slopes.
- Minimize overhead exposure; avalanches triggered by warming or cornice fall may be large and destructive.
- Extra caution is needed around cornices under the current conditions.
- Avoid exposure to steep, sun exposed slopes, especially when the solar radiation is strong.
Problems
Persistent Slabs
30-70 cm of snow sits over a crust/facet weak layer combination that is still possible to human trigger. Recent observations demonstrate the potential for this problem to be triggered remotely and to propagate far and wide if triggered. This layer is most reactive between 1700 and 2000 m but should be expected above and below this elevation band.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Cornices
Cornices are expected to become weak with daytime warming and solar radiation.
There may still be old wind slabs lingering in the alpine but the likelihood of triggering these old slabs continues to diminish with each day of the ongoing warming.
Aspects: All aspects.
Elevations: Alpine.
Likelihood
Expected Size
Loose Wet
Loose wet avalanches should be expected on steep, sun exposed slopes during the heat of the afternoon.
Aspects: South East, South, South West, West.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Feb 13th, 2022 4:00PM
