Avalanche Forecast
Issued: Dec 29th, 2019 3:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs and Wind Slabs.
cgarritty,
Avalanche Canada
Our persistent slab problems are slowly fading, but it's key to remember the high consequences of triggering. Maintain diligent group management and keep avoiding classic weak points like shallow rocky start zones and steep convexities if you're venturing into bigger terrain.
Summary
Confidence
Weather Forecast
Sunday night: Clear periods. Light southwest winds.
Monday: Becoming cloudy with isolated flurries bringing a trace of new snow during the day and increasing overnight. Light to moderate southwest winds increasing over the day. Alpine high temperatures around -7.
Tuesday: Cloudy with continuing flurries bringing new snow totals to 10-20 cm, continuing overnight. Light to moderate southwest winds. Alpine high temperatures around -7.
Wednesday: Cloudy with continuing flurries bringing 10-15 cm of new snow and 2 day snow totals to 35-50 cm, continuing overnight. Light to moderate southwest winds. Alpine high temperatures around -7.
Avalanche Summary
Reports from Saturday included a few observations of recent natural and skier-triggered wind slabs reaching size 2.5 (large). One wind slab release managed to trigger a very large (size 3) deep persistent slab on a steep, unsupported slope in the high alpine. Its crown fracture was 3 metres deep. All of the above occurred above 2200 metres.
The spectacularly large and destructive natural avalanche cycle observed during last week's big storm has for the most part ended but persistent slabs have shown continued reactivity to explosives and other large triggers.
Snowpack Summary
In exposed areas at higher elevations, recent moderate southwest winds have formed some isolated wind slabs with the 10-30 cm of low density snow we received late last week. Elsewhere this recent snow remains unconsolidated. The interface below it may present as a sun crust on steep sun-exposed aspects or as a more widespread melt-freeze crust below about 1700 metres.
100 to 160 cm of snow is now resting on a widespread layer of large, feathery, surface hoar from mid-December. This layer was the primary failure plane in the very large and destructive natural avalanche cycle observed during and after the big storm two weekends ago. Activity on this interface has largely tapered off and is this layer is suspected to be trending towards dormancy.
Another weak layer composed of a combination of surface hoar, crust & facets formed in late November is now over 170 cm deep and is presently inactive.
Terrain and Travel
- Avalanche hazard may have improved, but be mindful that deep instabilities are still present.
- Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
- Avoid convexities, steep unsupported terrain and rocky outcroppings.
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
Problems
Persistent Slabs
Settled snow from previous storms has formed a slab on weak surface hoar 100 to 160 cm below the surface. Natural avalanche activity has waned, but human triggering may still be possible in suspect areas such as shallow, rocky start zones or steep convexities. This avalanche problem is too deep in the snowpack for you to feel under your skis, track or feet.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Wind Slabs
10-30 cm of recently fallen snow coupled with moderate southwest wind has likely formed fresh wind slabs in exposed alpine terrain features.
Aspects: North, North East, East, North West.
Elevations: Alpine.
Likelihood
Expected Size
Valid until: Dec 30th, 2019 5:00PM
