Avalanche Forecast
Regions: Bull, Crowsnest North, Crowsnest South, Elkford East, Elkford West, South Rockies.
Reactive wind slabs likely exist at upper elevations. Watch and feel for signs of instability such as whumpfing, cracking, and recent avalanches.
Concern remains for the persistent weak layers near the base of the snowpack. A conservative approach to terrain is advised.
Confidence
Low
Avalanche Summary
No recent avalanche reports on Tuesday.
On Sunday, explosive control produced a large size 2.5 wind slab avalanche on a southeast aspect in the alpine. This avalanche gouged down to the faceted lower snowpack in its track and as a result, entrained a large amount of mass.
Looking forward, we expect human-triggered wind slabs will remain possible, especially where new snow and wind are forming fresher, more reactive slabs. Consider the fact that these slabs have the potential to 'step down' to the faceted lower snowpack, resulting in larger avalanches.
We have very few eyes out there. If you do get out please consider reporting in the MIN.
Snowpack Summary
Up to 10 cm of new low-density snow fell across the region overnight Monday with dribs and drabs to follow all week. The new snow accompanied by changing winds (strong from the NW and now switching to the WSW) may have formed fresh and reactive wind slabs in the alpine and at treeline.
This snow overlies a previously heavily wind-affected surface in open areas. In the alpine, many windward slopes may have been stripped back to early-season layers or rock.
30-60 cm of snow sits on top of a weak, sugary, faceted lower snowpack. Cold temperatures have weakened and faceted the snowpack as a whole. A rain crust sits near the ground.
Total snowpack depths at treeline elevations are 50-80 cm.
Weather Summary
Tuesday Night
Dribs and drabs overnight. Westerly winds 50-80 km/h at ridgetop. Temperatures are steady near -15 C.
Wednesday
Cloudy with isolated flurries. Westerly winds 50-80 km/h at ridgetop. Temperatures slightly warming to -11 C and freezing levels valley bottom.
ThursdayMostly cloudy with possible sunny breaks. Lingering snow flurries up to 5 cm. Strong to extreme Westerly winds at ridgetop. Westerly winds 20-40 km/h at ridgetop. Temperatures reach a high of -10 C.
FridayCloudy with snowfall, up to 5 cm of accumulation. Westerly winds 30-60 km/h at ridgetop. Treeline temperatures reach a high of -10 C.
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.
- Back off if you encounter whumpfing, hollow sounds, or shooting cracks.
- If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
Avalanche Problems
Wind Slabs
New snow and strong wind may form fresh and reactive slabs in lee areas at upper elevations. Dry loose sluffing may be seen from steep slopes and terrain features.
Small avalanches may trigger a bigger avalanche by 'stepping down' to the weak and faceted crystals buried deeper within the snowpack.
Aspects: North, North East, East, South East, South.
Elevations: Alpine, Treeline.
Likelihood: Possible - Likely
Expected Size: 1 - 2
Persistent Slabs
The lower snowpack is composed of weak, sugary facets. Avalanches on this layer are possible where a cohesive slab (as opposed to loose, powdery snow) exists above these facets.
Observations on this layer are currently limited. In times of uncertainty such as this, our best defense is to keep terrain choices conservative.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Possible
Expected Size: 1.5 - 3