Avalanche Forecast
Issued: Mar 20th, 2023 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Persistent Slabs.
lbaker,
Avalanche Canada
Hazard is improving as temperatures drop down to the valley bottom but be mindful that deep instabilities are still present.
Use caution around wind loaded terrain where windslab may be reactive to skier traffic.
Summary
Confidence
Avalanche Summary
On Sunday, a suspected skier triggered avalanche was reported. This was a size 1 storm slab avalanche that likely occurred on Saturday.
Through the weekend we continued to receive reports of evidence of large storm slab and wind slab avalanches, size 2-3, in both Haines Pass and White Pass. These avalanches may have occurred during the storm or due to solar input and elevated freezing levels through the weekend.
If you head out in the backcountry, let us know what you are seeing by submitting a report to the Mountain Information Network.
Snowpack Summary
Up to 50 cm of storm snow at White Pass and +50 cm at Haines Pass from last week has settled rapidly with warm temperatures. Storm totals taper inland in both regions. Local wind patterns have varied from southerly in White Pass to easterly in Haines Pass, building wind slabs in exposed lee terrain. This overlies previously wind affected snow (sastrugi) in exposed areas and faceted snow in sheltered features.
A buried weak layer of surface hoar can be found about 80 cm deep in Powder Valley, Tutshi, and Paddy Peak areas, 150 to 200 cm around White Pass and 80-200 cm deep in Haines Pass. This layer is most prominent on northerly slopes sheltered from the wind. On other aspects, this layer is a hard melt-freeze crust with weak facets around it. This layer has been most problematic in alpine terrain.
The remainder of the middle of the snowpack is consolidated and strong. Weak faceted grains are found near the base of the snowpack, particularly in thin snowpack areas.
Weather Summary
Monday Night
Cloudy with isolated flurries, 1-3 cm accumulation. Moderate southwest winds. Alpine temperature low -6°C. Freezing levels drop to valley bottom.
Tuesday
Mainly cloudy. Strong southwest winds. Alpine temperature high -7°C. Freezing levels valley bottom.
Wednesday
Cloudy with isolated flurries, 1-3 cm accumulations. Strong southwest winds. Alpine temperature high -4°C. Freezing levels 600 m.
Thursday
Cloudy with isolated flurries, trace accumulations. Strong south winds. Alpine temperature high -3°C. Freezing levels 800 m.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Fresh wind slabs will likely form throughout the day, diligently watch for changing conditions.
- Be carefull around freshly wind loaded features.
- Be careful with wind slabs, especially in steep, unsupported and/or convex terrain features.
- Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
Problems
Wind Slabs
Wind slabs formed by storm snow and southeast winds linger on north and west facing terrain features. Though natural avalanche activity has tapered off they remain possible to human trigger.
Observe the wind loading pattern in the area as you move through the terrain, southwest winds Tuesday will redistribute available snow into fresh wind slabs in lees through the day.
Aspects: North, North East, East, South West, West, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
A weak layer of surface hoar and/or faceted grains around a hard crust sit in the mid snowpack. This layer is buried around 80 cm in the eastern portions of the region and up to 200 cm around White Pass and Haines Pass.
This layer has previously produced widely propagating avalanches in alpine terrain and it is capable of being remotely triggered from a distance. The most likely area for riders to trigger it is in wind-sheltered, north-facing terrain, and in rocky terrain where the snowpack is thin.
Aspects: All aspects.
Elevations: Alpine.
Likelihood
Expected Size
Valid until: Mar 21st, 2023 4:00PM
