Avalanche Forecast
Regions: Sea To Sky.
Slabs formed on Thursday may take a bit of time to bond to previous surfaces. Watch for storm slabs in sheltered terrain and wind slabs on lee slopes. Don't discount the power of the sun, and cornices are likely large and looming.
Confidence
High - Confidence is due to a stable weather pattern with little change expected.
Weather Forecast
THURSDAY NIGHT: Cloud with snowfall then clearing, accumulation 2 to 5 cm, moderate southwest wind, alpine temperature -10 C.
FRIDAY: Mix of sun and cloud, light southwest wind, alpine temperature -10 C, freezing level 900 m.
SATURDAY: Early-morning snowfall then a mix of sun and cloud, accumulation 5 to 10 cm, light southwest wind, alpine temperature -10 C, freezing level 700 m.
SUNDAY: Mostly clear skies, light west wind, alpine temperature -10 C, freezing level 800 m.
Avalanche Summary
A few small (size 1) wind and storm slab avalanches were triggered by humans on Wednesday. They occurred in alpine terrain, on northerly aspects, and were up to 25 cm thick.
Although we do not have reports yet of avalanche activity from Thursday, it is suspected that many storm and wind slab avalanches were triggered naturally and by humans within the new storm snow. Natural avalanche activity should decrease on Friday, with the exception of sun-exposed slopes during intense sunny conditions. Human-triggering of avalanches may remain likely on Friday.
Snowpack Summary
Thursday's storm dropped around 20 to 30 cm of snow across the region. The snow fell with strong to extreme south to southwest wind, forming wind slabs in lee terrain features at treeline and alpine elevations.
A weak layer of surface hoar crystals and/or faceted grains may be found around 50 to 80 cm deep on northerly aspects at treeline and lower alpine elevations. The layer may have been destroyed by strong wind immediately before burial on February 22nd, but it may still exist in sheltered terrain features in parts of the region. Where it is found, it has been reactive in snowpack tests. This persistent weak layer warrants investigation and a conservative terrain use strategy. Check out the latest forecaster blog that offers a deeper dive into these conditions.
Weak faceted snow and melt-freeze crusts exist near the base of the snowpack in some of the region, particularly the eastern and northern parts. This layer is considered dormant, as it hasn't produced an avalanche since February 20th. This layer may require a very large load, such as a cornice fall, or rapid weather changes to reactivate it.
Terrain and Travel
- Continue to make conservative terrain choices while the storm snow settles and stabilizes.
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Be aware of the potential for large avalanches due to the presence of buried surface hoar.
- Surface hoar distribution is highly variable. Avoid generalizing your observations.
- Pay attention to cornices and give them a wide berth when traveling on or below ridges.
Avalanche Problems
Storm Slabs
Around 20 to 30 cm of snow from Thursday has started to consolidate into a slab in sheltered terrain. In exposed terrain at higher elevations, the snow fell with strong to extreme south to west wind, forming wind slabs in lee terrain features. These slabs may remain touchy to human traffic on Friday. Sun-exposed slopes should be treated as suspect during periods of intense sun. Cornices have also likely grown large and could fail during sunny conditions or from the weight of a human.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Possible - Likely
Expected Size: 1 - 2.5
Persistent Slabs
A weak layer of feathery surface hoar may be found around 50 to 80 cm deep on northerly aspects around treeline and lower alpine elevations. This layer may be spotty and only found in sheltered terrain features in parts of the region. Assess the layer in the snowpack prior to committing to avalanche terrain or adopt a conservative mindset to avoid the problem.
Aspects: North, North East, East, West, North West.
Elevations: Alpine, Treeline.
Likelihood: Unlikely - Possible
Expected Size: 2 - 3