Avalanche Forecast
Regions: Crawford, Dogtooth, East Purcell, Esplanade, Purcells, St. Mary, West Purcell.
Uncertainty is best managed through conservative terrain choices at this time.
Avoid steep, convex terrain and rocky areas where triggering is more likely.
Confidence
Moderate
Avalanche Summary
On Monday, a skier triggered a small but deep, persistent slab avalanche in the Crawford area. The size 1 avalanche occurred on a northwest aspect at treeline.
There have been numerous natural and skier triggered very large(up to size 3) persistent slab avalanches reported on all aspects at treeline and above in the Esplanade range over the past week. They have been failing on a weak layer of surface hoar down 50-70 cm.
Snowpack Summary
5-15 cm of recent snow and strong west wind formed wind slabs on lee features at treeline and above.
The primary layer of concern in much of this region is a weak layer of surface hoar down 50-70 cm. This layer may be less likely to trigger in areas that have a strong, supportive crust above.
In the southern portion of the region, weak facets near the ground may be the primary layer of concern. Especially in shallow, rocky areas in the alpine.
Average snowpack depths at treeline are 70-120 cm which tapers rapidly below treeline.
Weather Summary
Tuesday Night
Mostly clear skies with no precipitation, southwest alpine wind 10 to 25 km/h, treeline temperature -6 °C.
Wednesday
Mostly sunny skies, southwest alpine wind 30 to 40 km/h, treeline temperature -5 °C.
Thursday
Partly cloudy with isolated flurries, up to 2cm of snow, southwest alpine wind 40 to 50 km/h, treeline temperature -4 °C.
Friday
A mix of sun and cloud with isolated flurries, trace amounts of snow, southwest alpine wind 30 km/h, treeline temperature -4 °C.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Avoid shallow snowpack areas, rock outcroppings and steep convex terrain where triggering is most likely.
- Surface hoar distribution is highly variable. Avoid generalizing your observations.
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
Avalanche Problems
Persistent Slabs
The primary layer of concern in much of the region is a layer of surface hoar down 50-70 cm. If triggered avalanches on this layer could step down to deeper weak layers.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Possible
Expected Size: 1.5 - 3
Wind Slabs
Lingering wind slabs may remain reactive to human triggers in isolated locations in the alpine.
Aspects: North, North East, East, South East, South.
Elevations: Alpine.
Likelihood: Possible
Expected Size: 1 - 2
Deep Persistent Slabs
A layer of weak facets near the ground may be reactive to human triggering. Especially in shallow, rocky areas in the alpine areas where the layer is not being capped by a crust.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Unlikely - Possible
Expected Size: 1.5 - 3