Avalanche Forecast
Issued: Mar 20th, 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
Expect southwesterly winds and flurries to form fresh slabs around ridges and lee features. Be mindful that best riding conditions may overlap with the deepest deposits and touchiest slabs.
Summary
Confidence
Moderate - Uncertainty is due to the timing, track, & intensity of the incoming weather system.
Weather Forecast
SATURDAY NIGHT: Isolated flurries, up to 5 cm. Light to moderate southwest wind, alpine temperature low -11C, and freezing level dropping to valley bottom.
Weather models are showing a band of moisture moving from the Shuswap to the Purcells through the Nakusp area late Saturday evening and overnight, and may produce enhanced precipitation in localized areas near the South Columbia and Rogers Pass Forecast Regions of up to 15cm.Â
SUNDAY: Cloudy with flurries, up to 10 cm of snow during the day and into Sunday night. Light to moderate southwest wind, alpine high -5C, and freezing level beginning near valley bottom rising to about 1400 m.
MONDAY: Cloudy and lingering flurries, 5 cm. Light northwest wind, alpine high -5C, and freezing level beginning near valley bottom rising to about 1500 m.
TUESDAY: Mostly sunny with patchy clouds. Moderate southwest wind, alpine high 0C, and freezing level beginning near valley bottom rising above 1500 m.
Avalanche Summary
A few small loose wet avalanches were reported on Wednesday and Thursday on solar aspects. 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
5-15 cm fresh snow accumulated around the region Saturday and covers dry snow and surface hoar (up to 15 mm) on northerly aspects above 1800m, and crusts on solar aspects and lower elevations. Flurries and wind have formed fresh slabs in immediate lees. Large cornices may still pose a hazard close to alpine ridgelines, especially when it's warm and sunny.
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.
- A moist or wet snow surface, pinwheeling and natural avalanches are all indicators of a weakening snowpack.
Problems
Wind Slabs
Southwest winds and new snow have formed wind slabs in lee terrain features. This problem may increase in sensitivity over as new snow and wind continue to build the slab. Steep, convex slopes below alpine ridge tops are the most likely places to trigger these slabs.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine.
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. They are most likely to fail during intense periods of solar radiation. Cornice failures are very unpredicatble.
Aspects: North, North East, East.
Elevations: Alpine.
Likelihood
Expected Size
Valid until: Mar 21st, 2021 4:00PM
