Avalanche Forecast
Issued: Mar 11th, 2023 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Deep Persistent Slabs.
jsmith,
Avalanche Canada
Easterly winds formed wind slabs on lee aspects in the alpine.
Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
Summary
Confidence
High
Avalanche Summary
A couple cornice failures that did not trigger slabs on the slopes below and small (size 1) rider triggered wind slab avalanches in the alpine were reported on Friday.
A cornice triggered size 3 deep persistent slab avalanche was reported on the northeast face of Mt. Mackenzie on Thursday. See MIN.
Snowpack Summary
Easterly wind has formed small wind slabs on lee aspects at treeline and above. Sun crust on sunny slopes and surface hoar (3-10 mm) on shady slopes at all elevations. Previous wind effect in open areas at treeline and above.
The mid-snowpack is generally strong but the lower snowpack is a different story. The November facets are still prominent at the base of the snowpack. They are showing signs of rounding but there is still a considerable step in resistance between them and the overlying snow. These facets are most pronounced in shallow rocky areas.
Weather Summary
Saturday Night
Cloudy with isolated flurries; 5-10 cm / Light southwest ridgetop wind / Low temperature at treeline around -10 C / Freezing level valley bottom.
Sunday
Mix of sun and cloud / Light southwest ridgetop wind / High temperature at treeline around -2 C / Freezing level 1300 m.
Monday
Snow; 15-25 cm; + 10-20 cm overnight / Strong southwest ridgetop wind / High temperature at treeline around 2 C / Freezing level rapidly rising to 1800 m.
Tuesday
Mix of sun and cloud / Moderate west ridgetop wind / High temperature at treeline around -3 C / Freezing level 1200 m.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
- Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.
- Avalanche hazard may have improved, but be mindful that deep instabilities are still present.
Problems
Wind Slabs
Easterly winds have formed wind slabs on lee aspects in the alpine.
Aspects: South, South West, West, North West.
Elevations: Alpine.
Likelihood
Expected Size
Deep Persistent Slabs
A weak layer of facets exists near the base of the snowpack. The likelihood of human triggering is low given the layer's depth, but large triggers such as cornice failures or smaller avalanches in motion have the potential to produce very large avalanches with surprisingly wide propagation. Suspect terrain for human triggering includes steep, shallow, and rocky terrain where the snowpack transitions from thin to thick.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Mar 12th, 2023 5:00PM
