Avalanche Forecast
Issued: Mar 21st, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Cornices.
dsaly,
Avalanche Canada
Carefully assess your line for reactive wind slabs before committing. Steep, convex slopes below ridgetop are the most likely places to trigger these slabs.
Summary
Confidence
Moderate - Uncertainty is due to the speed, direction, or duration of the wind and its effect on the snowpack.
Weather Forecast
SUNDAY NIGHT: Snow and flurries, most areas should see 5-10 cm however localized enhancement may produce up to 20 cm in isolated areas. Moderate southwest wind, alpine low -8C, and freezing level beginning near 1000 m.
MONDAY: Cloudy with lingering flurries and sunny breaks, up to 5 cm. Light west-northwest wind, alpine high -6C, and freezing level rising above 1500 m.
TUESDAY: Mostly sunny with patchy clouds. Light southwest wind, alpine high 0C, and freezing level beginning near valley bottom rising above 1500 m.
WEDNESDAY: Cloudy with flurries, 5-10 cm. Light northwest wind, alpine high -3C, and freezing level rising to 1500 m during the day.
Avalanche Summary
On Sunday, dry loose avalanches failed naturally and were reactive to skiers with fresh low density snow sliding on crusts or compact surfaces.
On Saturday, several naturally size 1.5 wind slabs were observed on northeasterly aspects in the alpine. Sluffing and dry-loose avalanches were reported in steep terrain.
A few small loose wet avalanches were reported Wednesday through Friday on solar aspects into the alpine. A small wind slab was also reported from a high elevation east facing aspect Thursday.
On Tuesday, natural cornice falls were observed. Reports indicated that they did not pull a slab on the slope below. Sunshine may initiate loose wet avalanches on steep solar slopes and continue to weaken cornices.
Snowpack Summary
South-southwesterly winds have impacted loose snow developing slabs in immediate lees. 5-15 cm fresh snow covers dry settled snow on northerly aspects above 1800m, and crusts on solar aspects and lower elevations. Loose snow is sluffing easily on the crust. Large cornices loom over alpine ridgetops. Below 1300 m, the snowpack is moist.
A persistent weak layer of facets 40-60 cm deep that was buried in mid-February was reactive in the north of the region earlier this month but since the first week of March, only a couple of avalanches have been reported on this layer resulting from large triggers such as cornice fall. There are several other weak layers deeper in the snowpack composed of old surface hoar, facets and/or crusts, all of which have been recently unreactive.
Terrain and Travel
- Avoid freshly wind loaded features, especially near ridge crests, roll-overs and in steep terrain.
- Wind slabs are most reactive during their formation.
- Avoid exposure to slopes that have cornices overhead.
- Dial back your terrain choices if you are seeing more than 25cm of new snow.
- A moist or wet snow surface, pinwheeling and natural avalanches are all indicators of a weakening snowpack.
Problems
Wind Slabs
Recent southwest winds and new snow have formed wind slabs in lee terrain features. Winds are expected to transition to a west-northwesterly flow, which may encourage "reverse loading" building fresh wind slabs on more south and easterly slopes. Steep, convex slopes below alpine ridge tops are the most likely places to trigger these slabs.
Aspects: North, North East, East, South East, South, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Cornices
Where cornices exist they pose a threat both from the potential to collapse under your feet (or machine) and from the potential to send large chunks of snow far down a slope. If anything can trigger the more stubborn persistent weak layers it's a large falling cornice.
Aspects: North, North East, East.
Elevations: Alpine.
Likelihood
Expected Size
Valid until: Mar 22nd, 2021 4:00PM
