Avalanche Forecast
Regions: South Rockies.
Less solar input is expected on Monday, but some elevation bands may not get a good overnight re-freeze. Move off slopes before they get wet and slushy. Consecutive days in a row of warm temperatures may increase the reactivity of deeper weak layers and cornices.
Confidence
Moderate - Uncertainty is due to difficult to forecast freezing levels. Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.
Weather Forecast
SUNDAY NIGHT: Partly cloudy, light to moderate west wind, alpine low -2 C, freezing level dropping to 1700-1800 m in the am, potential for near freezing layer at surface overnight.
MONDAY: Increasing cloud, flurries/light rain possible, 0-5mm, light easterly wind, alpine high 0 C, freezing level 1900-2000 m.
TUESDAY: Mostly sunny, light to moderate west wind, alpine high +2 C, freezing level 2200 m.
WEDNESDAY: Mostly sunny, light to moderate southerly wind, alpine high +2, freezing level 2200 m.
Avalanche Summary
There were wet loose avalanches size 1.5-2 from south and west facing alpine terrain reported in the South Rockies on Saturday.
Snowpack Summary
Wind slabs in the alpine may linger, especially on northerly aspects. Snow on all solar aspects and elevation bands has been getting moist by mid morning and may not be getting a good overnight re-freeze of late. Snow on northerly terrain above 1500 m has so far remained dry, but this could change on Monday depending on the snow rain line and freezing levels. Cornices are large and looming, and glide cracks are increasing in size...both should be considered unpredictable and given a wide berth.
Around 30 to 60 cm of snow sits above a persistent weak layer of sugary faceted grains that was buried in mid-February. There have been a handful of avalanches that released on this layer in the past few weeks. There is another persistent weak layer that was buried at the end of January, found around 50 to 80 cm deep. This layer consists of feathery surface hoar, facets, and/or a hard melt-freeze crust. Periodic avalanches continue to be triggered on these layers by riders, particularly where a stiff wind slab sits above them. Check out this MIN that shows the positioning of the layers in the snowpack near Crowsnest Pass.
Weak faceted snow and a decomposing melt-freeze crust can be found near the base of the snowpack.Â
Terrain and Travel
- Be alert to conditions that change with aspect and elevation.
- Use caution on large alpine slopes, especially around thin areas that may propagate to deeper instabilities.
- Cornices become weak with daytime heating or solar exposure.
- Be alert to conditions that change throughout the day.
Avalanche Problems
Persistent Slabs
Consecutive days of warm temperatures without a solid overnight re-freeze may reactivate persistent weak layers from January and February. Widespread avalanche activity has already occurred on the layers, but they could still be triggered anywhere they haven't already failed. Look for signs of instability and continue treating the snowpack as suspect if you are uncertain whether the layer is still present in your riding area.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Possible
Expected Size: 1.5 - 2.5
Loose Wet
Sunny breaks, warm temperatures and potential light rain may weaken the upper snowpack and form wet loose avalanches, especially if we don't get a good overnight re-freeze. Pinwheeling and a moist snow surface are signs that the stability of the upper snowpack is decreasing.
Even small avalanches can be a hazard in high consequence terrain and above terrain traps.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Possible - Likely
Expected Size: 1 - 2
Cornices
Cornices are large and likely weakening with sustained elevated freezing levels and significant daytime heating. Big cornice falls are a hazard on their own but can also trigger large persistent slab avalanches on the slopes below.
Aspects: North, North East, East, West, North West.
Elevations: Alpine.
Likelihood: Possible
Expected Size: 1.5 - 2.5