Avalanche Forecast
Regions: Akamina, Flathead, Lizard, Lizard-Flathead.
Reactive wind slabs may exist at upper elevations. Watch and feel for signs of instability such as whumpfing, cracking, and new avalanches. If you seek more sheltered areas at treeline you should consider that this is where the persistent slab has been most reactive in snowpack tests. Keep your terrain choices conservative and assess conditions while you travel.
Confidence
Moderate
Avalanche Summary
On Tuesday no natural avalanches were reported, however, a few skier-controlled and explosive controlled wind slabs up to size 1 were seen.
Last Sunday, a MIN report from Tunnel Creek reported reactivity in a snowpack test on the Mid-November layer on a south aspect. They also observed a large natural avalanche on a west-facing slope at treeline.
With continued moderate to strong winds and slightly warmer temperatures, wind slabs may be present and reactive on Thursday as well as loose dry avalanches (sluffing) of the surface snow from steep slopes and terrain features.
Snowpack Summary
Up to 20 cm of low-density snow fell by Wednesday morning. This new snow will add to the ~25 cm of storm snow that fell early in the weekend. In wind-affected terrain, westerly winds are expected to redistribute this new snow building fresh wind slabs. In sheltered terrain, slightly warmer temperatures may start to consolidate the recent snow into more of a slab.
The middle of the snowpack consists of weak sugary layers of facets and surface hoar. A widespread rain crust remains near the ground at treeline and below treeline.
At treeline, snowpack depths vary from 120-200 cm.
Weather Summary
Wednesday Night
Unsettled weather overnight bringing up to 5 cm of new snow. Westerly winds 15-25 km/h at ridgetop. Temperatures near -9 C and freezing levels valley bottom.
Thursday
Cloudy with isolated flurries. Moderate to strong southwesterly winds at ridgetop. Temperatures reach a high of -4 C.
FridayNew snow 5-10 cm. Southwest wind 20-40 km/h with stronger gusts. Average temperature near -8 C.
SaturdayA mix of sun and cloud. Flurries. Winds generally light from the southwest. Treeline temperatures reach a high of -5 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.
- Expect slab conditions to change drastically as you move into wind exposed terrain.
- Back off if you encounter whumpfing, hollow sounds, or shooting cracks.
- Fresh snow rests on a problematic persistent slab, don't let good riding lure you into complacency.
Avalanche Problems
Wind Slabs
Strong westerly winds combined with new snow may build reactive wind slabs in the alpine and open areas at treeline.
Small avalanches in the upper snowpack could trigger deeper weak layers, creating a larger than expected avalanche.
Aspects: North, North East, East, South East, South.
Elevations: Alpine, Treeline.
Likelihood: Possible - Likely
Expected Size: 1 - 2
Persistent Slabs
Buried layers of surface hoar and facets have been reactive to human triggers in recent days. Reactivity has been observed in sheltered areas at treeline, where the surface hoar may be preserved, and in wind-loaded areas at upper elevations, where a cohesive slab has been formed above.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Possible
Expected Size: 1 - 2.5