Avalanche Forecast
Issued: Feb 3rd, 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
Wind slabs will continue to form at higher elevations.
Approach steep open slopes at treeline and below with caution. A buried surface hoar layer may be reactive and can produce larger avalanches than you expect. Watch for signs of instability as you travel.
Summary
Confidence
Moderate - We are confident about the possible sizes of avalanches, should one release; what is less certain is the likelihood of triggering.
Weather Forecast
Light snowfall is forecast for Friday. Temperatures rise and skies clear for the weekend.
THURSDAY NIGHT: A mix of sun and clear breaks, moderate westerly winds. Freezing level at valley bottom. Isolated flurries.Â
FRIDAY: Mostly cloudy, with up to 5 cm expected, favouring the north. Strong westerly winds. Freezing level around 500 m. Alpine high of -6.Â
SATURDAY: Another 5cm by Saturday morning is possible, with strong westerly winds. A mix of sun and cloud. Freezing level rises towards 1200 m. High of -5.Â
SUNDAY: Mostly clear with strong westerly winds. Freezing level rises towards 1900 m, with a high of 0.
Avalanche Summary
On Wednesday, riders triggered slabs to size 1. Remote triggers were also reported, producing small slab avalanches failing on the buried surface hoar layer. Small natural wind slabs were also observed in steep terrain features.Â
Natural wind slabs have been observed throughout the week, during peak loading from strong westerly winds. Loose dry avalanches have also been reported, from steep terrain features.
Snowpack Summary
At lower elevations, 20-40 cm of storm snow sits over a melt freeze crust. In sheltered terrain a widespread layer of large surface hoar crystals sits immediately above the crust, which may be sensitive to human triggers.Â
At higher elevations the storm snow has been redistributed into pockets of wind slab by strong westerly winds. A thin melt freeze crust extends into the alpine on solar aspects. This crust may sit on the surface in exposed terrain, or below wind deposited snow in sheltered features increasing reactivity.
Several surface hoar layers are now buried in the upper snowpack 30-60cm deep. The early December crust/facet layer of concern sits around 80 cm deep in the eastern Purcells and shallow terrain, and up to 150 cm in the west. This layer produced numerous large avalanches in January, and is now considered dormant. We will continue to track this layer of concern and expect it will wake up again with major warming or a large storm event. This recent forecaster blog goes into more details on the layer and how to manage it.Â
Terrain and Travel
- Approach steep open slopes at and below treeline cautiously, buried surface hoar may exist.
- Look for signs of instability: whumphing, hollow sounds, shooting cracks, and recent avalanches.
- Be alert to conditions that change with elevation and wind exposure.
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
Problems
Persistent Slabs
Fresh snow sits over a large and sensitive surface hoar. On south facing aspects this may sit on a crust. Treat open slopes at treeline and below with caution - they may be more reactive and produce larger avalanches than you expect. Shooting cracks or whumpfing are clear signs to keep terrain choice conservative.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Wind Slabs
Fresh wind slabs may build with continued strong westerly winds and new snow. Expect reactivity where they overly a smooth crust, or a weak surface hoar layer in sheltered terrain features.
Look for wind loading in unusual places, as direction has varied from northwest to southwest and stronger wind speeds may load mid slope features.
Aspects: North, North East, East, South East, South, South West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Feb 4th, 2022 4:00PM
