Avalanche Forecast
Issued: Apr 26th, 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.
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Avalanche Canada
Cariboos, Kootenay Boundary, Lizard-Flathead, North Columbia, North Rockies, Purcells, South Columbia, South Rockies, Blue River, Clearwater, McBride, Premier, Quesnel, Sugarbowl, Clemina, Esplanade, Jordan, North Monashee, North Selkirk, Shuswap, Badshot-Battle, Central Selkirk, Goat, Gold, Kokanee, North Okanagan, Retallack, Valhalla, Whatshan, Dogtooth, East Purcell, Moyie, St. Mary, West Purcell, Bonnington, Grohman, Kootenay Pass, Norns, Rossland, South Okanagan, Ymir, Akamina, Flathead, Lizard, Bull, Crowsnest North, Crowsnest South, Elkford East, Elkford West, Kakwa, McGregor, Pine Pass, Renshaw, Robson, Tumbler, Glacier.
Rising temperatures will increase the avalanche danger and potentially trigger very large avalanches. Read more in this Forecasters' Blog.
Summary
Confidence
Moderate
Avalanche Summary
Recent observations are limited to small wet loose avalanches on sun-exposed slopes. Starting Thursday we expect rapid warming to cause a natural cycle of wet avalanches and cornice failures as well as the potential for very large persistent and deep persistent slab avalanches.
Snowpack Summary
Moist surfaces can be expected everywhere except the highest north-facing slopes.
The sudden addition of heat to the snowpack has potential to reawaken 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. The Purcells likely require minimal heat to trigger large avalanches, while other parts of the interior have been experiencing a period of dormancy and may take longer to react to the warming.
The snowpack is diminishing below treeline, but under the current conditions persistent and deep persistent slab avalanches could release at higher elevations and run into valley bottoms.
Weather Summary
Thursday
A high pressure ridge is bringing mostly sunny skies (except partly cloudy in the Cariboos and North Rockies) with freezing levels climbing to 2500 m in southeastern BC and 2000 m in the North Rockies.
FridaySunny with freezing levels sustained at 3500 m in southeastern BC and 2500 m in the North Rockies.
SaturdaySunny with freezing levels sustained at 3500 m in southeastern BC and 3000 m in the North Rockies.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Avoid steep slopes when air temperatures are warm, or solar radiation is strong.
- 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
The likelihood of very large avalanches releasing on buried weak layers will increase with each day of warming. Layers of concern include weak snow above crusts buried in late March (50 to 100 cm deep) and weak facets at 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 daytime warming and during periods of strong sun. This problem can quickly change over the day. Stable conditions in the morning can turn very unstable during the heat of the day.
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: Apr 27th, 2023 4:00PM
