Avalanche Forecast
Issued: Mar 19th, 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
Steer clear of steep and consequential slopes, give the snowpack time to adjust to the new load of recent heavy snow and warm temperatures.
Watch for reactivity in wind loaded features, and be aware of the buried layers potential to produce large, wide propagating avalanches.
Summary
Confidence
Avalanche Summary
We continue to receive reports of large storm slab and wind slab avalanches, size 2-3, that likely occurred within the storm earlier this week in both Haines Pass and White Pass.
No new avalanches were reported yesterday though wind slabs remain possible to human trigger.
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
Around 50 cm of storm snow has fallen around White Pass, with lesser amounts as you move east. Southerly winds have built deeper deposits on north facing terrain features near ridges.
In Haines Pass upwards of 50 cm of storm snow fell, with rain on snow occurring below 700 m. Storm totals also taper inland here, with winds rapidly redistributing snow and leaving soft snow to be found in sheltered gullies and side valleys.
In all areas, storm snow is settling with warm temperatures. 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. To date this layer is 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
Sunday Night
Cloudy with scattered flurries, 6 cm expected for Haines and 2 cm for White Pass. Moderate southeast winds. Alpine temperature low -4°C. Freezing levels reach 800 m.
Monday
Cloudy with isolated flurries, 1-3 cm accumulations. Moderate south winds. Alpine temperature high -3°C. Freezing levels 1000 m.
Tuesday
Cloudy with clear periods. Strong southwest winds. Alpine temperature high -7°C. Freezing levels 500 m.
Wednesday
Mainly cloudy with isolated flurries, 1-3 cm accumulations. Strong southwest winds. Alpine temperature high -5°C. Freezing levels 700 m.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Stay off recently wind loaded slopes until they have had a chance to stabilize.
- Be carefull around freshly wind loaded features.
- Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
- Conditions may have improved, but be mindful that deep instabilities are still present.
Problems
Wind Slabs
Up to 50 cm of storm snow with strong southerly winds has formed reactive wind slabs on north and west facing terrain features. Observe the wind loading pattern in the area as you move through the terrain, local wind patterns have varied from southerly in White Pass to easterly in Haines Pass.
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 20th, 2023 4:00PM
