Avalanche Forecast
Issued: May 1st, 2023 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Deep Persistent Slabs, Cornices and Loose Wet.
mconlan,
Avalanche Canada
A high freezing level is destabilizing the snowpack, triggering numerous different avalanche problems. Check out the latest Forecasters' Blog for more information.
Summary
Confidence
Moderate
Avalanche Summary
We've seen widespread wet loose and cornice avalanche releases, of which some has stepped down to buried weak layers, producing very large avalanches. We expect this trend to continue. See here, here, and here for a couple examples from the weekend.
Riders should expect wet loose avalanches and cornice failures during periods of warm air and sunny skies. 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, which is unlikely to freeze overnight.
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
Tuesday is warm with mostly clear skies and a freezing level to 3700 m. Wednesday is mostly cloudy with a freezing level around 3500 m. Thursday has a freezing level around 3300 m with mostly sunny skies.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Avoid exposure to overhead avalanche terrain as temperatures increase.
- The likelihood of deep persistent slab avalanches will increase with each day of warm weather.
- 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.
- A moist or wet snow surface, pinwheeling and natural avalanches are all indicators of a weakening snowpack.
- The more the snowpack warms-up and weakens, the more conservative you`ll want to be with your terrain selection.
Problems
Deep Persistent Slabs
The likelihood of very large avalanches releasing on a weak layer buried near the base of the snowpack is increasing 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 isn't a good overnight refreeze. 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
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
Loose Wet
Wet loose avalanche activity is expected with daytime warming and during periods of strong sun. This problem can quickly change over the day. Limit your exposure to steep terrain when the snow feels sloppy.
Wet slabs are also possible, particularly on sun-exposed slopes where a buried melt-freeze crust exists in the upper snowpack.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: May 2nd, 2023 4:00PM
