Avalanche Forecast
Issued: May 5th, 2023 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Deep Persistent Slabs, Loose Wet and Cornices.
mconlan,
Avalanche Canada
Intense warming over the past week has destabilized the snowpack, and it may take a while for the snowpack to adjust. Be aware of the various avalanche problems you could come across during spring weather.
Summary
Confidence
Avalanche Summary
We've seen widespread wet loose, wet slab, and cornice avalanche releases, of which some has stepped down to buried weak layers, producing very large avalanches. See here, here, and here for a few examples from last weekend. It is possible that similar avalanches could occur during the heat of the day.
Riders should expect wet loose and slab avalanches and cornice failures during periods of warm air and rain. Avoiding steep slopes when the snow feels sloppy and avoiding cornice exposure are good travel habits.
The likelihood of seeing very large avalanches releasing on a buried weak layer increases with each day of warming. This is particularly true for days without an overnight surface refreeze. Humans are most likely to trigger this layer in steep and rocky slopes where the snowpack is relatively thin.
Snowpack Summary
The snow surface is moist to at least the low alpine, which may freeze into a hard melt-freeze crust overnight. Upwards of 5 to 10 cm of new snow may have accumulated in the high alpine on Friday.
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 are weakening with intense warming.
Weather Summary
The freezing level between Saturday and Monday is around 2000 m. Saturday and Sunday are mostly cloudy with isolated flurries and Monday is a mix of sun and cloud with isolated flurries.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.
- Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.
- Avoid exposure to overhead avalanche terrain, avalanches may run surprisingly far.
- Avoid steep slopes when air temperatures are warm, it is raining, or solar radiation is strong.
- Avoid terrain traps such as gullies and cliffs where the consequence of any avalanche could be serious.
Problems
Deep Persistent Slabs
Very large avalanches could release on a weak layer buried near the base of the snowpack. 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 but may be most likely during the heat of the day. Resulting avalanches could travel far and even into snow-free valleys. For this reason, recognizing and avoiding areas with large overhead avalanche slopes, even if they are out of sight, is very important.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Loose Wet
Wet loose and wet slab avalanche activity is possible during periods of rain or sunny skies. Limit your exposure to steep terrain when the snow feels sloppy.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Cornices
Cornices are large at this time of year and will become more prone to fail as they warm up with spring weather. Stay well back from them when on ridgelines and limit your exposure when travelling on slopes below them, as their release is unpredictable. Remember that a flat spot on a ridgeline could be an overhanging cornice. Cornice falls could trigger very large slab avalanches on slopes below them.
Aspects: North, North East, East, West, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: May 6th, 2023 4:00PM
