Avalanche Forecast
Issued: Mar 18th, 2022 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs and Wind Slabs.
wlewis,
Avalanche Canada
Buried weak layers are keeping danger ratings elevated, particularly in the southern half of the region.
Watch for signs of instability like whumpfing, natural avalanches and cracking.
Summary
Confidence
Weather Forecast
FRIDAY NIGHT: Partly cloudy, with flurries. Freezing levels drop to 800 m. Light to moderate southwesterly winds.
SATURDAY: A mix of sun and cloud. Flurries continue, around 5 cm of snow. Freezing levels rising to 1500 m. Moderate southwesterly winds. Alpine high of -1.
SUNDAY: Around 5 cm overnight. Mostly sunny with moderate northwest winds. Freezing levels reach 1200 m, alpine high of -3.
MONDAY: Scattered flurries with cloudy skies. Moderate southwest winds. Freezing levels reach 1500 m.
Avalanche Summary
On Thursday, natural avalanche activity was observed up to size 2 in alpine features near Valemount. Storm snow was reactive to human triggers, producing avalanches up to size 1.
On Wednesday, natural and human triggered activity was observed to size 2 in wind loaded features. Avalanches were naturally and remotely triggered (from a distance), and mostly occurred on south facing slopes around treeline. However of note, a size 3 was remotely triggered on a northeast aspect near McBride. While the layer of concern is only 40 cm deep, this produced a large avalanche with impressive propagation.
On Tuesday numerous natural and human-triggered storm slabs were reported. These mainly occurred on north-facing (shaded) aspects in the alpine and treeline and failed on a buried weak layer of surface hoar.
Snowpack Summary
Up to 70 cm of recent settling storm snow sits over a layer of weak surface hoar in sheltered and shaded terrain, and over a crust on south facing slopes. The new snow is bonding poorly to this old surface, producing propagating results on testing and large avalanches within the last 3 days.
At higher elevations consistent southwest winds are creating deeper deposits on north through east facing features. Below 1300 m, moist snow or a melt-freeze crust likely exists from recent rain and warm temperatures.
The lower snowpack is generally well-settled and strong in most areas, with crust layers 50 to 100 cm deep.
Terrain and Travel
- Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
- Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
- Avoid freshly wind loaded features, especially near ridge crests, roll-overs and in steep terrain.
Problems
Persistent Slabs
New snow continues to add load to a weak layer buried 30-60 cm deep. Large avalanches have been triggered on these layers within the last 3 days.
- A layer of crust and facets can be found at all elevations on sun affected slopes (south through east)
- On other aspects, a large layer of surface hoar may be preserved on sheltered treeline slopes.
The most reactivity has been seen in the McBride, Valemount and Blue River area. More information can be found here in the new forecaster blog.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Wind Slabs
Recent snow and moderate southwest winds have formed wind slabs at higher elevations.
These slabs may be surprisingly deep and propagate widely where they are sitting on a weak layer of surface hoar or a sun crust.
Aspects: North, North East, East, South East, South, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Mar 19th, 2022 4:00PM
