Avalanche Forecast
Issued: Mar 17th, 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 continue to be reactive to triggers. Stick to conservative terrain with minimal overhead hazard and watch for signs of instability like whumpfing, natural avalanches and cracking.
Find more information on this tricky layer here.
Summary
Confidence
Moderate - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.
Weather Forecast
THURSDAY NIGHT: Flurries continue, around 5cm of snow. Freezing levels drop to 500 m overnight. Moderate southwesterly winds.Â
FRIDAY: Partly cloudy, with isolated flurries. Freezing level rising to 1500 m. Light to moderate southwesterly winds. Alpine high of -1.
SATURDAY: A mix of sun and cloud. Flurries continue, up to 5 cm of snow. Freezing levels rising to 1600 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.Â
Avalanche Summary
On Wednesday, natural activity was observed to size 2 in wind loaded features.
Several avalanches were reported on the buried weak layer of surface hoar or facets on a crust. 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.Â
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.Â
Snowpack Summary
30-60 cm of settling storm snow is being redistributed into wind loaded features at higher elevations. At lower elevations moist snow or a melt-freeze crust likely exists from recent rain and warm temperatures.
This new snow is sitting on various surfaces, including hard wind-affected snow, sun crusts on southerly slopes, facetted snow, and isolated pockets of surface hoar. The new snow is bonding poorly to this old surface, producing large avalanches within the last 3 days.Â
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.
- On south facing slopes a layer of crust and facets can be found at all elevations.
- On other aspects, a large layer of surface hoar is most concerning 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 18th, 2022 4:00PM
