Avalanche Forecast
Issued: Nov 25th, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Deep Persistent Slabs.
mark herbison,
Strong to extreme winds and recent snow will keep the avalanche hazard elevated in the alpine.
Watch for sluffing in steep, confined terrain.
Uncertainty surrounds the Nov 5 crust /facet layer and what it will take to become reactive.
Summary
Weather Forecast
Mainly cloudy for Thursday with isolated flurries accumulating up to 2cm of snow. Winds will be from the West - North West in the 30-70km/hr range. Temps will range from 0 in valley bottoms to -9 in the alpine. Friday will see a further increasing winds, up to 100 km/hr from the West, small amounts of snow and slightly warmer temperatures.
Snowpack Summary
10-20cm of new snow, along with 25-40km/hr W-SW winds is building wind slab at treeline and above. The Nov 5 facet/crust combo is down 50-80 cm and producing variable test results from easy to hard, but 'sudden' in fracture character. The Nov crust extends up to 2500 m on N aspects and higher on solar aspects. Snow depths at treeline are 50-130 cm.
Avalanche Summary
Natural wind slab avalanche activity observed up to size 2 from steep rocky terrain in the Ogden area today.
Local ski areas reporting wind slabs up to size 1.5 from explosive control work.
Confidence
Problems
Wind Slabs
With fresh snow available for transport and increasing Westerly winds, anticipate to find reactive wind slabs on lee and cross loaded features.
- If triggered the wind slabs may step down to deeper layers resulting in large avalanches.
- Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
Aspects: North, North East, East, South East, South, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Deep Persistent Slabs
The deeper Nov.5 crust has facets growing above and below it, and exists up to 2500m on shady aspects and higher on solar aspects. Where there is a dense slab overlying this layer, it remains a concern and likely will be for the foreseeable future.
- Be aware of thin areas that may propogate to deeper instabilites.
- Pay attention to overhead hazards like cornices which could trigger the deep persistent slab.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Nov 26th, 2020 4:00PM
