Avalanche Forecast
Issued: Apr 1st, 2023 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Deep Persistent Slabs and Wind Slabs.
wlewis,
Avalanche Canada
Watch for small but reactive wind slabs as you gain elevation.
Small wind slabs may trigger larger avalanches on deeply buried weak layers. Continue to avoid wind affected, thin and rocky terrain.
Summary
Confidence
Avalanche Summary
On Friday a size 3 naturally triggered avalanche was reported in the Dogtooth Range. While the failure plane is unknown the report mentions impressive propagation, likely on a buried persistent weak layer.
On Thursday a natural cornice fall (from strong sunshine) triggered a loose dry avalanche to size 2. Several naturally triggered ice falls have also been reported this week - while they have not triggered avalanches they are hazardous on their own.
No activity on the deeply buried weak layers has been reported this week. However thin and rocky terrain features in the upper treeline and alpine should still be avoided.
Snowpack Summary
New snow and wind are forming wind slabs at higher elevations, over a melt freeze crust (on all aspects at low elevations, and on sun affected slopes to mountain top). On north facing slopes at treeline and alpine, new snow sits over previously wind affected surfaces. Surface hoar may exist below the recent snow, in wind sheltered and shaded terrain - increasing reactivity.
The mid snowpack holds several persistent weak layers that vary throughout the Purcells, including layers of surface hoar in wind-sheltered terrain and sun crusts on south facing slopes. No recent activity has occurred on these layers, but they may remain triggerable in isolated features.
The lower snowpack includes a widespread layer of large, weak facets and or depth hoar crystals. This weak layer has been responsible for a number of very large, destructive avalanches this season, including several last week during warm temperatures and will continue to be a concern for the rest of the season.
Weather Summary
Saturday Night
Cloudy. Light snowfall brings up to 5 cm. Moderate southwesterly wind gusting strong. Freezing level drops to valley bottom.
Sunday
Mostly cloudy with flurries with trace accumulations. Freezing levels rise to 1300 m with alpine highs of -7 °C. Light west winds.
Monday
Partly cloudy. Light easterly winds. Freezing levels rise around 1300 m.
Tuesday
Clearing skies with 1300 m freezing levels. Light easterly winds.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.
- If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
- Pay attention to cornices and give them a wide berth when traveling on or below ridges.
Problems
Deep Persistent Slabs
The base of the snowpack remains very weak. Very large human-triggered avalanches are possible at treeline and above. Avoid thin, rocky start zones and shallow areas with variable snowpack depths.
Deep persistent avalanches are challenging to predict. This layer can suddenly become active again, typically when there is rapid change or stress to the snowpack - sudden warming, heavy snow or rainfall, or heavy loads eg. cornice fall.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Wind Slabs
Wind slabs exist at treeline and above, from new snow and southwest winds. Watch for reactivity on north and east facing slopes near ridgelines.
Small wind slabs have the potential to step down to deeper weaknesses within the snowpack.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Apr 2nd, 2023 4:00PM
