Avalanche Forecast
Issued: Feb 16th, 2023 7:30AM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Persistent Slabs.
trettie,
Avalanche Canada
Carefully assess the wind effect as well as new snow amounts as you move through terrain. Ongoing snowfall and southerly winds are adding to the wind slab problem.
Summary
Confidence
Avalanche Summary
We received reports of numerous small to large (size 1 to 2) wind slabs triggered by riders and naturally in lee terrain features over the past few days. Slabs on Tuesday were 30 to 50 cm deep around treeline and propagated widely.
Check out this MIN from our field team that discusses the wind slab problem in greater detail.
On Friday, a large avalanche was triggered by riders, likely releasing on the weak layer described in the Snowpack Summary. See this MIN for details and photos, highlighting the propagation potential and high consequence nature of this layer.
Snowpack Summary
Another 20cm of storm snow with Southerly winds adds to the previous 80cm that has already been redistributed into wind slabs on northerly aspects. Southerly slopes are generally scoured or wind pressed. In sheltered areas the above mentioned snow is still soft and likely makes for decent riding.
A hard melt-freeze crust that extends up to about 1700 m is now on the snow surface in wind-exposed terrain and otherwise buried about 50 to 80 cm in wind-loaded terrain. The crust appears to be bonding to the snowpack.
A weak layer of surface hoar and facets may be buried about 80 to 120 cm deep on north to east aspects in alpine and upper treeline elevations. The layer may rest on a harder melt-freeze crust. Where preserved, this layer has shown to have very high propagation potential and capable of producing large avalanches hundreds of metres wide.
Weather Summary
Thursday Night
Cloudy with light flurries bringing up to 5cm of new snow. Light to moderate southwest winds and a low of -9 at 1500m.
Friday
Stormy with 5 to 15cm of new snow expected. Moderate southwest winds and a high of -5 at 1500m.
Saturday
Mostly cloudy with light flurries bringing a few centimeters of new snow. Moderate to strong westerly winds and a high of -6 at 1500m.
Sunday
A few clouds and the possibility of light flurries bringing trace amounts of new snow. Light to moderate westerly winds and a high of -7 at 1500m.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Watch for areas of hard wind slab on alpine features.
- Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
- The best and safest riding will be on slopes that have soft snow without any slab properties.
- Remote triggering is a big concern, be aware of the potential for wide propagations and large, destructive avalanches at all elevations.
Problems
Wind Slabs
Ongoing snowfall with southerly winds have continued to build reactive wind slabs on northerly aspects while cross loading others.
Aspects: North, North East, East, South East, West, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
We continue to see periodic avalanches on a weak layer of surface hoar and facets buried about 100 cm deep. Resulting avalanches have propagated for hundreds of metres, with some being remotely triggered from hundreds of metres away. The common trend is that they are on north to east aspects around 1500 to 1700 m in elevation.
Aspects: North, North East, East, North West.
Elevations: Alpine.
Likelihood
Expected Size
Valid until: Feb 17th, 2023 4:00PM
