Avalanche Forecast
Issued: Mar 4th, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Persistent Slabs.
ahanna,
Avalanche Canada
Wind slabs and cornices have been reactive lately and will continue to build Thursday with new snowfall and strong winds. A buried weak layer continues to be reactive in most areas, producing larger avalanches as it gets buried deeper.
Summary
Confidence
Weather Forecast
Wednesday night: Isolated flurries bringing up to 5 cm new snow. Moderate northwest wind. Freezing level valley bottom.
Thursday: 5-15 cm new snow with heaviest amounts in in the east. Strong southwest wind. Freezing level 1300 m.
Friday: 5-10 cm new snow. Light southwest wind. Freezing level 500 m.
Saturday: Mix of sun and cloud. Light variable wind. Freezing level valley bottom.
Avalanche Summary
On Monday and Tuesday several large natural wind slabs size 2-3 were observed on northeast to southeast aspects in the alpine. Some were triggered by cornices failures.
Reports of persistent slab avalanches on the Feb 22 surface hoar have been coming in since the weekend, naturals size 2-3 on north to east aspects around treeline and below. Reports of skier triggered persistent slabs size 1-2 have dwindled somewhat since the weekend but this MIN report from Tuesday shows a sled triggered persistent slab avalanche at treeline.
Snowpack Summary
Incremental snowfall and strong winds continue to build deep pockets of fresh wind slab and cornices in the alpine and open areas at treeline.
A few sun crusts exist on solar aspects in the upper snowpack. A weak layer of widespread surface hoar sits 60-100 cm deep. There is uncertainty about the distribution and reactivity of this layer especially in the north of the region. Read more about surface hoar on our forecaster blog!
The early February melt-freeze crust down 80-120 cm has not been associated with avalanche activity but still gives results in snowpack tests.
Terrain and Travel
- Avoid freshly wind loaded terrain features.
- Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.
- Be aware of the potential for large avalanches due to the presence of buried surface hoar.
- Uncertainty is best managed through conservative terrain choices at this time.
Problems
Wind Slabs
Incremental snowfall and strong winds are building deep wind slabs in the alpine and open areas at treeline. If triggered, windslabs have the potential to trigger deeper weak layers.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
A weak layer of surface hoar sits 60-100 cm deep. (Read more about surface hoar on our forecaster blog) Natural persistent slabs size 2-3 and skier triggered size 1-2 have been running on this layer over the last few days even as professionals seek to actively avoid suspect terrain features (eg. convex rolls). Observations are concentrated on north to east aspects around treeline. This problem has been observed in all but the northern tip of the region, where there is uncertainty around the distribution of the surface hoar.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Mar 5th, 2020 5:00PM
