Avalanche Forecast
Issued: Mar 18th, 2023 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Deep Persistent Slabs.
jsmith,
Avalanche Canada
30-50 cm thick storm slabs formed earlier in the week may continue to be reactive to human triggers in specific locations at upper elevations.
Minimize exposure to sun-exposed slopes when the solar radiation is strong.
Summary
Confidence
High
Avalanche Summary
A remotely triggered size 2 storm slab avalanche was reported on a north aspect in the alpine on Friday. The slab was 30-40 cm deep and failed on a crust. See MIN.
Additionally, one natural and numerous explosive triggered cornice falls up to size 2.5 were reported on north aspects in the alpine. Most of them did not trigger slabs on the slopes below.
Snowpack Summary
Expect to find a melt-freeze crust on the surface of all aspects at treeline and below and on sunny aspects in the alpine. Solar radiation will break down the crust on sunny slopes throughout the day.
Strong solar radiation has settled the 30-50 cm of recent snow into a storm slab which has remained reactive to human triggers in specific locations at upper elevations.
Strong southwest wind during the storm earlier in the week added to slab formation on lee aspects at treeline and above.
The recent snow is sitting on a variety of surfaces. These include sun crust on sunny aspects and surface hoar (3-10 mm) on some shady and sheltered slopes.
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 improving but this layer remains a significant concern in rocky, shallow, or thin to thick snowpack areas at treeline and above.
Weather Summary
Saturday Night
Clear skies / 10 km/h east ridgetop wind / Temperature at treeline around -8 C / Freezing level valley bottom
Sunday
Sunny / 20 km/h east ridgetop wind / Temperature at treeline around -1 C / Freezing level 1800 m
Monday
Mix of sun and cloud / 10 km/h east ridgetop wind / Temperature at treeline around -3 C / Freezing level 1700 m
Tuesday
Mostly sunny / 10 km/h east ridgetop wind / Temperature at treeline around -5 C / Freezing level 1500 m
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Minimize exposure to sun-exposed slopes when the solar radiation is strong.
- Cornice failure may trigger large avalanches.
- Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
- A moist or wet snow surface, pinwheeling and natural avalanches are all indicators of a weakening snowpack.
- Storm slabs in motion may step down to deeper layers resulting in large avalanches.
Problems
Storm Slabs
30-50 cm thick storm slabs formed earlier in the week may continue to be reactive to human triggers in specific locations at upper elevations.
Aspects: All aspects.
Elevations: Alpine, Treeline.
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 19th, 2023 4:00PM
