Avalanche Forecast
Issued: Dec 28th, 2019 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Persistent Slabs.
shorton,
Avalanche Canada
Large storm slab avalanches are primed for human triggering. Stick to simple low-angle terrain.
Summary
Confidence
Weather Forecast
SATURDAY NIGHT: Scattered flurries with 5-10 cm of snow along the coast and up to 5 cm further inland, moderate wind from the southwest, alpine temperatures around -2 C.
SUNDAY: Scattered flurries with 5-10 cm of snow, light to moderate wind from the southwest, alpine high temperatures around -1 C.
MONDAY: Next frontal system arrives bringing 20-30 cm of snow by the afternoon, strong wind from the southwest, freezing level climbs to 1400 m.
TUESDAY: Stormy weather continues with another 25-40 cm of snow, strong wind from the southwest in the morning then easing to moderate in the afternoon, freezing level around 1400 m.
Avalanche Summary
Preliminary reports suggest a cycle of natural storm slab avalanches occurred in some parts of the region on Saturday (these areas received at least 30 cm of storm snow). Human triggered storm slabs will remain likely on Sunday. There is additional concern about buried surface hoar layers, as the combination of new snow, wind loading, and warming has likely increased the stress on these layers. If Saturday's storm didn't already result in persistent slab avalanche activity, then Monday and Tuesday's more intense storm likely will.
Snowpack Summary
Saturday's storm delivered 30-50 cm of snow to many parts of the region, with the exception of the Shames area that only received 15-20 cm. Strong wind from the southwest likely formed deeper deposits in lee terrain. This could be the extra load needed to wake up either of the two layers of surface hoar buried 50-120 cm deep. Reports from the Shames area suggest buried surface hoar can be found on all aspects, but is more prevalent on southeast to southwest aspects around 800-1400 m, as well as sheltered alpine areas. The lower snowpack is generally considered strong.
Terrain and Travel
- Use conservative route selection. Choose simple, low-angle, well-supported terrain with no overhead hazard.
- Use increased caution at all elevations. Storm snow is forming touchy slabs.
- Avoid freshly wind loaded features, especially near ridge crests, roll-overs and in steep terrain.
- Be aware of the potential for large avalanches due to the presence of buried surface hoar.
- Back off if you encounter whumpfing, hollow sounds, or shooting cracks.
Problems
Storm Slabs
20-50 cm of fresh snow and strong wind has formed widespread storm slabs. Human triggering is likely on steep, convex, and wind loaded slopes.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
New snow, wind loading, and warming has likely stressed weak layers of surface hoar buried 50-120 cm deep. Smaller avalanches may step down to these layers and produce large avalanches that propagate across entire terrain features.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 29th, 2019 4:00PM
