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. Forecast precipitation (either snow or rain) amounts are uncertain.
Weather Forecast
SUNDAY NIGHT: Snow and flurries, most areas should see 10 cm however localized enhancement may produce up to 25 cm in isolated areas. Moderate southwest wind, alpine low -9C, and freezing level near 1000 m.
MONDAY: Cloudy with lingering flurries and sunny breaks, up to 10 cm. Light to moderate northwest wind, alpine high -3C, and freezing level rising to about 1200 m.
TUESDAY: Mostly cloudy. Light to moderate southwest wind, alpine high -2C, and freezing level beginning near valley bottom rising to about 1400 m.
WEDNESDAY: Snow, 10-15 cm. Moderate southwest wind, alpine high -4C, and poor overnight recoveries with freezing level hovering around 1000 m overnight and rising above 1500 m during the day.
Avalanche Summary
On Sunday, explosives and skier traffic triggered numerous size 1 avalanches. A few small dry loose avalanches and sluffing in steep terrain was also reported.
On Saturday in Glacier NP, a handful of storm slabs size 1.5-2.5 released naturally from steep north-northwest aspects above 2000 m.
On Friday, several glide slab avalanches (size 2-3) were observed on south and east aspects around the TCH highway corridor. Loose wet avalanches to size 2.5 were reported around the region; a natural loose-wet cycle was reported around Rogers Pass initiating with evening rainfall.
Avalanche activity on Thursday was limited to two glide slabs to size 2.5 releasing around 1750 m on steep south facing slopes.
On Tuesday, a size 3.5 deep slab avalanche was reported from the Northern Monashees. It was triggered by cornice fall on an east-southeast aspect above 2200 m. Additionally, a natural glide slab size 2.5 was reported from a West aspect at 1500 m and numerous loose wet to size 2 in steep southerly terrain.Â
On Monday, numerous natural loose wet avalanches were reported from southerly aspects above 1900 m.
Snowpack Summary
Southwesterly winds have developed slabs in lee features. 20-35 cm storm snow covers a handful of surfaces: dry settled snow and surface hoar (up to 10 mm) on northerly aspects above 1800m, and crusts on solar aspects and lower elevations. Large cornices loom over alpine ridgetops. Below 1600 m, the snowpack turns moist.
Persistent weak layers of surface hoar, crusts, and/or facets 80-120 cm down have been unreactive and no recent avalanches have been reported on these layers.
Terrain and Travel
- Watch for wind-loaded pockets especially around ridgecrest and in extreme terrain.
- Wind slabs are most reactive during their formation.
- Pay attention to cornices and give them a wide berth when traveling on or below ridges.
- Dial back your terrain choices if you are seeing more than 25cm of new snow.
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. Carefully assess your line for touchy wind slabs before committing. Steep, convex slopes below alpine ridge tops are the most likely places to trigger these slabs.
Aspects: North, North East, East, South East, West, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Cornices
Where cornices exist they pose a threat both from the potential for them to collapse under your feet (or machine) and from the potential to send large chunks of snow far down a slope. They are most likely to fail during periods of solar radiation or loading from snow/wind.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine.
Likelihood
Expected Size
Valid until: Mar 22nd, 2021 4:00PM
