Avalanche Forecast
Regions: North Rockies.
Bundle up! A true arctic outbreak is upon us.
If you'd rather brave the cold than cozy up to a wood stove, then keep in mind that a persistent weak layer may continue to be reactive, in spite of the frigid weather. The layer is most prominent around treeline.
Confidence
Moderate - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast. Uncertainty is due to how quickly the snowpack will recover and gain strength.
Weather Forecast
MONDAY NIGHT - Mainly cloudy with clear periods / light northwest wind / alpine low temperature near -33Â
TUESDAY - A mix of sun and cloud with isolated flurries / light southeast wind / alpine high temperature near -27
WEDNESDAY - A mix of sun and cloud with isolated flurries / moderate northeast wind / alpine high temperature near -28
THURSDAY - Mainly sunny / strong to extreme northeast wind / alpine high temperature near -30
Avalanche Summary
There were a few small human triggered avalanches reported around treeline near Pine Pass on Sunday. These failed on the recently buried surface hoar layer.Â
There were some other observations from throughout the region over the weekend that would suggest ongoing instability associated with that weak surface hoar layer. Reports ranged from whumpfs and shooting cracks, to visual observations of large surface hoar crystals
On Wednesday and Thursday wind slab development was noted in the Kakwa, more details and images here.
On Wednesday there were reports of numerous natural avalanches 20 to 40 cm in depth running at and above treeline. A southwest slope produced a size 3 natural avalanche. These avalanches presumably ran on surface hoar which was producing very touchy conditions. There are some great visuals of this activity in this MIN.
Snowpack Summary
There is about 40-80 cm of snow resting on buried surface hoar which is most prevalent above 1600 m. It likely reaches into the alpine too, we're just not sure how high it extends.
Below 1600 m this snow sits on a crust.Â
There are presently no deeper concerns in the snowpack.
Terrain and Travel
- Shooting cracks, whumphs and recent avalanches are strong indicators of an unstable snowpack.
- Approach steep open slopes at and below treeline cautiously, buried surface hoar may exist.
- Fresh snow rests on a problematic persistent slab, don't let good riding lure you into complacency.
- Be careful as you transition into wind affected terrain.
Avalanche Problems
Persistent Slabs
A surface hoar layer buried near the end of January is now down 40 to 80 cm and has recently been quite sensitive to triggering. This layer has been the most sensitive right at treeline, but it is thought to extend into the alpine too.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Possible - Likely
Expected Size: 1.5 - 2.5
Wind Slabs
New snow last week with moderate to strong northwest wind formed wind slabs that may remain reactive in lee terrain features. These wind slabs may be sitting on top of weak surface hoar crystals in lower alpine and treeline areas, which would make them easier to trigger.
Aspects: North East, East, South East, South, South West, West.
Elevations: Alpine, Treeline.
Likelihood: Possible
Expected Size: 1.5 - 2.5