Avalanche Forecast
Issued: Apr 25th, 2023 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Cornices, Wind Slabs and Deep Persistent Slabs.
mconlan,
Avalanche Canada
Wintry conditions are found in the alpine, whereas spring-like problems are prominent at lower elevations. Travel cautiously and be aware of the various avalanche problems you could come across.
Summary
Confidence
Avalanche Summary
Many small to large (size 1 to 2) wet loose avalanches were observed over the weekend and on Monday, generally occurring out of steep alpine terrain. We expect to see similar avalanches in the coming days during periods of rain, sunny skies and an increasing freezing level. Small wind slabs may be possible to trigger in steep leeward alpine terrain on Wednesday.
The likelihood of seeing very large avalanches releasing on the buried weak layer described in the Snowpack Summary will increase with each day of warming this week. This is particularly true for days without an overnight refreeze. Humans are most likely to trigger this layer in steep and rocky slopes where the snowpack is relatively thin.
Also use plenty of caution along alpine ridges, where cornices are likely large and weakening.
Snowpack Summary
Rain will moisten the snow surface up to about 1800 m. Snow will accumulate at alpine elevations, which may be pushed into small wind slabs in lee terrain features with southwest wind.
The middle of the snowpack is consolidated with various layers of moist snow, hard snow, and melt-freeze crusts.
A layer of weak faceted grains is found near the base of the snowpack at treeline and alpine elevations.
Cornices are large and looming at this time of year and will weaken with daytime warming.
Weather Summary
Tuesday Night
Increasing clouds with no precipitation, 20 to 40 km/h southwest wind, treeline temperature 0 °C, freezing level 2000 m.
Wednesday
Cloudy with light snow or rain, accumulation 2 to 10 cm above the rain-snow line, 30 to 50 km/h southwest wind, treeline temperature 0 °C, freezing level 2000 m.
ThursdayMostly sunny with no precipitation, 10 to 20 km/h variable wind, treeline temperature 5 °C, freezing level rising to 3400 m.
FridaySunny with no precipitation, 10 km/h southeast wind, treeline temperature 10 °C, freezing level 3700 m.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Pay attention to cornices and give them a wide berth when traveling on or below ridges.
- Cornice failures could trigger very large and destructive avalanches.
- Carefully evaluate steep lines for wind slabs.
- The likelihood of deep persistent slab avalanches will increase with each day of warm weather.
- A moist or wet snow surface, pinwheeling and natural avalanches are all indicators of a weakening snowpack.
- Use caution above cliffs and terrain traps where even small avalanches may have severe consequences.
Problems
Cornices
Cornices are very large at this time of year and will weaken with rising freezing levels. Cornice falls are dangerous in their own right and they could trigger slabs on slopes below.
Wet loose avalanches are also possible at lower elevations where precipitation will fall as rain.
Aspects: North, North East, East, West, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Wind Slabs
New wind slabs may be found on steep lee terrain features wherever snow accumulates at treeline or alpine elevations. Assess for slabs prior to committing to any terrain with a potential high consequence.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Deep Persistent Slabs
The likelihood of very large avalanches releasing on a weak layer near the base of the snowpack will increase with each day of warming. Human triggered avalanches are most likely in steep, shallow, and rocky terrain where the snowpack is relatively thin. Naturally triggered avalanches could occur without warning and are most likely on days when there is isn't a good overnight refreeze. Resulting avalanches could travel far and even into snow-free valleys.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Apr 26th, 2023 4:00PM
