Avalanche Forecast
Issued: Dec 13th, 2022 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs and Wind Slabs.
CG,
Avalanche Canada
Why are forecasters pounding their palms and pontificating about persistent weak layers?!
There is uncertainty of if/when the tipping point will be reached on the persistent weak layers, which would likely result in the wide propagating avalanches seen adjacent to Rogers Pass.
Have a look at a blog from the Avalanche Canada forecasters on how to manage a persistent slab problem in the backcountry.
Summary
Confidence
Moderate
Avalanche Summary
More reports came in about unsupported pockets of soft slab failing on Dec 5 and Nov 17, mainly occurring around treeline and morainal features. Most avalanches were small (sz 1 or less), but still large enough to bury a person in a terrain trap.
Scary persistent slab incident in the RMR backcountry from Monday; see MIN report.
Snowpack Summary
Up to 40cm of settled snow now buries the Dec 5 layer, which consists of surface hoar, preserved stellars, facets, and a thin sun crust on steeper solar aspects.
The Nov 17th Surface Hoar is now buried 60-90cm and continues to produce sudden results in snowpack tests.
Weather Summary
The ridge over interior BC continues to hold, leaving us with a mix of sun/cloud, nil precipitation, temps ranging from -5*C to -9*C, and light ridge-top winds, switching from Westerly to Northerly. No snow is forecasted until possibly the weekend.
Terrain and Travel Advice
- Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
- Uncertainty is best managed through conservative terrain choices at this time.
- If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
Problems
Persistent Slabs
The Nov 17 and Dec 5 surface hoar are down ~75cm and ~35cm respectively, and most prevalent around tree line. These layers of surface hoar give 'sudden' results in snowpack tests; they have a propensity to propagate across continuous and broken features; and, they produce dramatic whumpfs in previously untraveled open glades.
Aspects: All aspects.
Elevations: Treeline, Below Treeline.
Likelihood
Expected Size
Wind Slabs
45cm of recent low density snow is available for transport. Isolated pockets of surface slabs may be found in Alpine and open Treeline lee features. Possible moderate Northerly winds on Wed may produce wind slabs on S-SW aspects
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 14th, 2022 4:00PM
