Avalanche Forecast
Issued: Jan 29th, 2023 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Deep Persistent Slabs, Wind Slabs and Persistent Slabs.
trettie,
Avalanche Canada
This challenging snowpack continues to produce avalanches. Stick to low-angle terrain away from any overhead hazard.
Read more in the latest Forecaster Blog.
Summary
Confidence
Moderate
Avalanche Summary
On Saturday several natural wind slabs, persistent slabs and deep persistent slabs up to size 3.5 were observed. These avalanches occurred late Friday through early Saturday morning and were triggered by wind loading or cornice falls in most cases.
On Friday, size 1-2 wind slab avalanches were triggered by riders and failed naturally, these were reported on northeast-east aspects above 2000 m. Riders also triggered a few persistent slab avalanches size 1-2, with crowns 50 cm deep and failing on surface hoar.
On Thursday, wind slab avalanches up to size 2 were reported occurring on all aspects above 2000 m. Basal facets continued to demonstrate reactivity with two large (size 2) natural deep persistent avalanches reported and explosives triggering a size 3 deep persistent avalanche, all occurring between 2000-2500 m.
On Monday, a fatal skier-triggered avalanche incident occurred in the Selkirk range near Revelstoke. The avalanche occurred on an east aspect at 1900 m, on a steep, open and unsupported slope. The size 2 avalanche had a crown depth of 50 cm and failed on surface hoar buried in early January.
High-consequence avalanche activity has been ongoing for several weeks. Your best defence is to stay diligent in choosing low-consequence terrain. Stick to slopes that have been heavily trafficked throughout the winter and avoid venturing into untouched zones. Stay disciplined and adjust your expectation for this winter.
Snowpack Summary
15-40 cm of recent snowfall over the last week has covered a layer of surface hoar and thin crust on solar aspects at treeline and above, and a supportive crust up to 1700 m around Revelstoke and increasing to 2000 m travelling south through the region. North and westerly winds have redistributed loose snow into wind slabs on south and east slopes.
Two layers of surface hoar which formed in early January are found 40-90 cm deep. These persistent weak layers have recently been reactive to human triggering, but snowpack tests are starting to indicate less propagation propensity. Deeper in the snowpack are two surface hoar/facet layers that were active earlier in the season, but recent snowpack observations suggest they are strengthening. The bottom of the snowpack is made up of large weak facets buried in late November, causing the Deep Persistent Slab problem for this region.
Weather Summary
Sunday Night
Clear skies with no new snow expected. Strong north to northwest winds and a low of -23 at 1800m.
Monday
Increasing cloud with up to 5cm of new snow expected. Moderate to strong northwest winds and a high of -13 at 1800m, possible temperature inversion with colder temps lower in valleys.
Tuesday
Stormy with 5 to 15cm of new snow expected. Moderate to strong west winds with a high of -12 at 1800m.
Wednesday
Stormy with up to 20cm of new snow expected. Moderate southwest winds and a high of -10 at 1800m.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Be mindful that deep instabilities are still present and have produced recent large avalanches.
- Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
Problems
Deep Persistent Slabs
A layer of large and weak facets sits near the base of the snowpack. This layer has been most problematic in upper treeline/lower alpine elevations. Riders are most likely to trigger an avalanche on this layer in steep, shallow previously undisturbed terrain or by first triggering a layer further up in the snowpack.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Wind Slabs
Northwest winds have formed wind slabs on south and east aspects while cross loading others.
Be aware that wind slab avalanches can step down to deeper layers.
Aspects: North, North East, East, South East, South, South West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
Numerous problematic weak layers exist in the top meter of the snowpack, with recent observations suggesting the most likely of these to trigger are surface hoar layers found 40-90 cm deep. Be especially cautious around steep convex openings at treeline and below.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Jan 30th, 2023 4:00PM
