Avalanche Forecast
Issued: Apr 11th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs, Cornices and Loose Wet.
ahanna,
Avalanche Canada
The spring sun can pack a punch and quickly initiate loose wet avalanche activity on steep slopes. Be ready to back off as the snow surface becomes moist. Lingering wind slabs may remain reactive to human triggers on lee features at alpine and treeline elevations.
Summary
Confidence
Moderate - Uncertainty is due to the limited number of field observations.
Weather Forecast
A ridge of high pressure sets up over the province bringing sunny, dry weather. Freezing levels are forecast to steadily rise through the week.
Sunday night: Clear. Light wind switching east. Alpine temperature around -9. Freezing level valley bottom.
Monday: Sunny. Light to moderate east wind. Alpine temperature around -6. Freezing level 1500 m.
Tuesday: Sunny. Moderate east wind. Alpine temperature around -3. Freezing level 1800 m.
Wednesday: Sunny. Moderate to strong east wind. Alpine temperature around 0. Freezing level 2500 m.
Avalanche Summary
Wind slabs have shown quite limited reactivity in the last couple of days, a few natural and ski cut size 1-1.5 were observed on Saturday. On Friday, most activity in the recent snow has been limited to size 1 loose snow avalanches. One size 2 was reported.
A couple of natural cornice failures size 2.5 observed Thursday did not trigger slabs on slopes below. One entrained loose dry to size 2.
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.
Snowpack Summary
20-30 cm of well-settled recent snow has been wind affected at upper elevations. 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
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
Cornices
Cornices are especially fragile this time of year, especially when the sun is out. Cornice falls are dangerous on their own and they can also trigger slabs on slopes below.
Aspects: North, North East, East, South East, North West.
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
Valid until: Apr 12th, 2021 4:00PM
