Avalanche Forecast
Issued: Apr 12th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Cornices, Loose Wet and Wind Slabs.
ldreier,
Avalanche Canada
It's going to be a sunny and warm day with freezing levels rising to 1900 m. Cornices are big and fragile and a hazard on their own if they fail. Be alert to changing conditions on sun exposed slopes during the heat of the day, especially if the snow becomes moist or wet.
Summary
Confidence
Moderate - Uncertainty is due to how the snowpack will react to the forecast weather.
Weather Forecast
A ridge of high pressure over the province brings sunny, dry weather. Freezing levels are forecast to steadily rise through the week.
Monday night: Clear, moderate southeast wind, alpine low -12 C, freezing level at valley bottom.
Tuesday: Sunny, moderate easterly wind, alpine high +2 C, freezing level 1900 m.
Wednesday: Sunny, moderate to strong east wind, alpine high +8 C, freezing level 2500 m.
Thursday: Sunny, moderate easterly wind, alpine high +10 C, freezing level 2600 m.
Avalanche Summary
Wind slabs were reactive over the weekend, several natural and ski cut size 1-1.5 and a few size 2 were observed on Saturday and Sunday. On Friday, most activity in the recent snow was limited to loose dry sluffing.
A couple of recent natural cornice failures size 2.5 did not trigger slabs on slopes below. One triggered small slab avalanches.
Neighboring Glacier National Park reported a few very large (size 3-4) glide slab releases on Thursday. Glide slabs are hard to predict and can release at any time so it is important to avoid slopes with glide cracks.
Last Tuesday, a natural size 3.5 wet slab was reported from an S-SW aspect at 2500 m to 1800 m along with numerous wet loose avalanches up to size 1. We can expect more activity like this in the heat this week.
Snowpack Summary
20-40 cm of well-settled recent snow has been wind affected at upper elevations. The snow surface consists of a crust on solar aspects and all aspects below 1800 m. On North aspects in the alpine, the recent snow sits on dry wintery snow surfaces and possibly surface hoar on wind-sheltered slopes. Elsewhere, it sits on a series of melt-freeze crusts on all aspects below 1900 m and southerly aspects to mountain top. Reports indicate snow is bonding well at these interfaces.
The recent warm weather is expected to have helped old persistent weak layers heal, including a few crusts buried over the last month as well as a facet layer 150 cm deep from the mid-February cold snap.
Terrain and Travel
- Avoid slopes when the solar radiation is strong, especially if they have large cornices overhead.
- Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.
- Rocks will heat up with daytime warming and may become trigger points for loose wet avalanches
- Small avalanches can have serious consequences in extreme terrain. Carefully evaluate your line for wind slab hazard before you commit to it.
Problems
Cornices
Cornices will become fragile with rising temperatures, especially when the sun is out. Cornice falls are dangerous in their own right and they can also trigger slabs on slopes below.
Aspects: North, North East, East, South East.
Elevations: Alpine.
Likelihood
Expected Size
Loose Wet
Surface snow can quickly lose cohesion and become unstable with solar warming during the day. Avoid exposing yourself to terrain where a small wet loose release could have big consequences.
Aspects: South East, South, South West.
Elevations: All elevations.
Likelihood
Expected Size
Wind Slabs
Lingering pockets of wind slab may be triggerable in unsupported terrain features.
Aspects: North, North East, East, South East, South.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Apr 13th, 2021 4:00PM
