Avalanche Forecast
Issued: May 4th, 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
Rain will continue to rapidly destabilize the snowpack, increasing the likelihood of large avalanches. Read more in the Forecasters' Blog.
Summary
Confidence
Avalanche Summary
An avalanche cycle of large to very large (size 2 to 4) wet loose and slab avalanches, cornice failures, and deep persistent slab avalanches continues over much of the region. We expect this cycle will continue over the coming days as rain soaks the snowpack.
Snowpack Summary
Rain will continue to wet the snowpack.
The intense addition of heat to the snowpack is reawakening dormant weak layers, including weak snow above crusts buried in late March (50 to 100 cm deep) and the weak basal facets found at the bottom of the snowpack. The timing of when and where persistent slabs will reawaken is uncertain, but will increase with each day of warming.
The snowpack is diminishing below treeline, but persistent and deep persistent slab avalanches could release at higher elevations and run into valley bottoms.
Weather Summary
A trough of low pressure will bring cloudy skies with 10 to 20 mm of rain and a freezing level near 3000 m for Friday. Precipitation continues into the weekend with a freezing level decline to 2000 m.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Travel in alpine terrain is not recommended.
- Minimize exposure during periods of heavy loading from rain.
- Minimize exposure to overhead avalanche terrain, large avalanches may reach the end of runout zones.
- Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.
- The more the snowpack warms-up and weakens, the more conservative you`ll want to be with your terrain selection.
- The likelihood of deep persistent slab avalanches will increase with each day of warm weather.
Problems
Deep Persistent Slabs
Expect very large avalanches to release on buried weak layers as intense warming destabilizes the snowpack. Layers of concern include weak snow above hard crusts buried about 50 to 100 cm deep and weak facets near the bottom 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 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
Loose Wet
Wet loose avalanche activity is expected with strong rain. Wet slabs are also possible, particularly where a buried melt-freeze crust exists in the upper snowpack.
Aspects: All aspects.
Elevations: All elevations.
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. Cornice falls could trigger very large slab avalanches on slopes below them.
Aspects: North, North East, East, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: May 5th, 2023 4:00PM
