Approach wind loaded features with caution, especially around treeline where fresh slabs may sit on a persistent weak layer.
With lots of loose snow for transport, moderate to strong southwest winds are forming wind slabs in lees. Watch for signs of instability such as whumpfing, cracking, and recent avalanches.
A layer of concern formed in mid-November is composed of faceted grains, surface hoar, and/or a hard crust and can be found down 40 to 70 cm. Each incremental snowfall and wind event is adding an additional load bringing the weak layer closer to its tipping point. As a cohesive slab builds above the weak layer it could quickly become reactive to natural or human triggers.
No new avalanches have been reported on the persistent weak layer, but we've had reports of shooting cracks and whumpfing at treeline. With very few field observations, there is great uncertainty around this layer and professionals have their guard up.
On Sunday operators in the region reported a natural windslab avalanche cycle to size 2 from the previous 24 to 48 hours.
Thank you for all the MIN reports! They are extremely helpful to us in the early season when snowpack information is limited. Please continue to share your observations via the Mountain Information Network
Small inputs of new snow continue to accumulate, bringing recent totals to 20 - 40 cm in sheltered areas at treeline. Where winds have redistributed fresh snow, soft slabs are forming in lee terrain features.
A weak layer of surface hoar, facets, and/or melt-freeze crust can be found down 40-70 cm. This layer is more likely to be reactive where wind distribution has created a cohesive slab over it.
Snowpack depths range from 70 cm at treeline to 140 cm in the alpine. Below treeline snowpack is thin and faceted creating an additional challenge when accessing higher areas.
Thursday night
Cloudy with scattered flurries bringing around 5 cm of new snow. Southwesterly ridge top winds 40 to 50 km/hr. Alpine temperature low -10.
Friday
Broken skies with scattered flurries bringing a trace of new snow. Southwesterly ridge top winds 30 to 40 km/hr. Alpine temperature high of -8.
SaturdayCloudy with flurries bringing up to 5 cm. Ridgetop winds gusting to 70 km/hr from the southeast. Alpine high temperature -6 and a low of -12.
SundayMostly cloudy. Calm. Alpine high temperature -8 and a low of -16.
More details can be found in the Mountain Weather Forecast.
