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
Weather Forecast
SUNDAY NIGHT: Snow and flurries, most areas should see 10-15 cm however localized enhancement may produce up to 25 cm in isolated areas. Moderate southwest wind, alpine low -6C, and freezing level near 1000 m.
MONDAY: Cloudy with sunny breaks and isolated flurries, up to 10 cm of snow possible. Moderate northwest wind, alpine high -4C, and freezing level rising above 1300 m.
TUESDAY: Mostly sunny with patchy clouds. Light to moderate southwest wind, alpine high +1C, and freezing level beginning near valley bottom rising above 1500 m.
WEDNESDAY: Snow, 10-20 cm. Light west wind, alpine high -1C, and rising to 1500 m.
Avalanche Summary
On Sunday, explosives and skier traffic triggered numerous size 1 avalanches, new and touchy cornices were observed. A few small dry loose avalanches and sluffing in steep terrain was also reported.
On Saturday, explosives triggered small (size 1-1.5) storm slabs from north-northeast aspects above 2000 m. A skier also triggered a small (size 1) wind slab on a steep convex roll on an easterly aspect at treeline. Sluffing was reported in steep terrain. In Glacier NP, a handful of storm slabs size 1.5-2.5 released naturally from steep north-northwest aspects above 2000m.
On Friday, several glide slab avalanches (size 2-3) were observed on south and east aspects around the TCH highway corridor. Loose wet avalanches up to size 2.5 were reported around the region; a natural loose-wet cycle was reported around Rogers Pass initiating with evening rainfall.
On Thursday several loose wet avalanches to size two were reported on solar alpine features. Pin wheeling was also noted on north aspects below 2000 m in the afternoon.
On Wednesday a few loose-wet avalanches were seen on steep solar aspects below treeline.
On Tuesday, a natural 1.5 loose wet avalanche was reported from steep rocky terrain and small loose-dry sluffs were easily triggered by skier traffic on northerly aspects.
Snowpack Summary
Southwesterly winds have developed slabs in lee features. 25-35 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 1500 m, the snowpack turns moist.
Persistent weak layers of surface hoar, crusts, and/or facets 80-120 cm down have recently been unreactive and no recent avalanches have been reported on these layers.
Terrain and Travel
- Dial back your terrain choices if you are seeing more than 25cm of new snow.
- Closely monitor how the new snow is bonding to the old surface.
- Look for signs of instability: whumphing, hollow sounds, shooting cracks, and recent avalanches.
- Avoid freshly wind loaded features, especially near ridge crests, roll-overs and in steep terrain.
- Pay attention to cornices and give them a wide berth when traveling on or below ridges.
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
New cornice development with touchy characteristics were observed on Sunday. 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
