Avalanche Forecast
Issued: Dec 29th, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs and Wind Slabs.
shorton,
Avalanche Canada
With fresh snow on the way keep in mind we are concerned about buried weak layers. Cautious terrain selection remains important.
Summary
Confidence
Moderate - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.
Weather Forecast
A weak frontal system crosses the region on Wednesday then a bigger system is poised to hit the region on the weekend.
TUESDAY NIGHT: Increasing cloud with snow starting around 3 am, moderate southwest wind, temperatures around -8 C.
WEDNESDAY: Flurries with 5-10 cm of snow, moderate southwest wind, temperatures around -6 C.
THIURSDAY: Flurries end early in the morning then mostly cloudy in the afternoon, moderate west wind, temperatures around -5 C.
FRIDAY: Flurries starting midday with a trace of new snow by the end of the day, moderate south wind, temperatures around -5 C.
Avalanche Summary
No new avalanches were reported on Monday, but a few skier triggered size 1 slab and loose avalanches were reported over the weekend. Many storm and persistent slab avalanches were observed last week. They were generally large (size 2), on west, north, and east aspects, 20 to 70 cm thick, and at elevations between 2000 and 2300 m. Although avalanche activity appears to have diminished, I wouldn't rule out the possibility of seeing more persistent slab avalanches.
Snowpack Summary
Stormy weather on Wednesday will bring 5-10 cm of new snow and could form new wind slabs in leeward terrain. Two weak layers are buried in close proximity to one another. They are 50-80 cm deep around Nelson and 30-50 cm deep around Rossland and other western parts of the region. The layers are composed of feathery surface hoar and sugary faceted grains and they overly a hard melt-freeze crust. There was substantial avalanche activity on these layers prior to Christmas from natural and human triggers. Although reports of such avalanches have been dwindling, these weak layers remain a concern, as they can produce large and destructive avalanches.
Terrain and Travel
- Be aware of the potential for large avalanches due to the presence of buried persistent weak layers.
- Use conservative route selection and resist venturing out into complex terrain.
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
Problems
Persistent Slabs
Weak layers of surface hoar and/or faceted grains overlie a hard melt-freeze crust 30 to 80 cm deep. The new snow load before Christmas pushed this problem over the tipping point and resulted in large avalanches. Although the likelihood of triggering persistent slab avalanches is decreasing, the potential for triggering a high consequence avalanche should still be top of mind in your decision making process.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Wind Slabs
Watch for new snow and wind to form reactive slabs on leeward terrain in the alpine and near ridgetops.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 30th, 2020 4:00PM
