Avalanche Forecast
Issued: Mar 18th, 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.
zryan,
Avalanche Canada
Uncertainty surrounding buried weak layers in the eastern part of the region is best managed with conservative terrain choices and good travel habits.
Reactive wind slabs may exist at upper elevations. Be cautious as you transition into wind-affected terrain.
Summary
Confidence
Moderate - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.
Weather Forecast
Active weather continues, with a series of frontal systems moving inland bringing light to moderate amounts of new snow.
FRIDAY NIGHT: Cloudy with snowfall, up to 5 cm of accumulation. Light to moderate southwesterly winds. Freezing level 1000 m.Â
SATURDAY: Snowing, 5-10 cm of accumulation. Moderate to strong southwesterly winds. Freezing level rising to 1500 m, dropping to 500 m overnight.
SUNDAY: Partially cloudy, light flurries. Moderate westerly winds easing in the afternoon. Freezing level rising to 1500 m, dropping to 500 m overnight.
MONDAY: Snowing, 5-10 cm of accumulation. Light to moderate southwesterly winds. Freezing level rising to 1500 m.
Avalanche Summary
Wind slabs are expected to form throughout the day and be reactive to human-triggering in the alpine and exposed areas at treeline.
There have been some notable human-triggered avalanches north of Nelson the past few days in the South Columbia region (read more in this blog). These have been larger storm slabs above weak layers, and we are uncertain whether these are signs of a developing persistent slab avalanche problem that could begin impacting northern and eastern parts of the Kootenay Boundary region as well.
A natural cycle occurred during Tuesday's storm. The cycle involved many large storm slab avalanches in the top 20 to 40 cm of snow (size 2). On Wednesday, activity was limited to a few natural slab and loose avalanches triggered by warming on south-facing slopes (size 1 to 2).
Snowpack Summary
10 to 15 cm of new snow overlies last week's 30 to 50 cm of denser, more settled snow. There is uncertainty about how well last week's snow is bonding to underlying layers. In the Selkirks, especially north of Nelson, it appears this snow could be bonding poorly to underlying crust and surface hoar layers. In the Monashees, it appears this snow has formed a stronger bond to underlying crusts. At this point, it appears persistent slab problems could be developing in the deeper snowpack areas in the Selkirks. There are several other crust layers found 30 to 70 cm deep, and it appears the snow is mostly well bonded to these crusts.
Terrain and Travel
- Uncertainty is best managed through conservative terrain choices at this time.
- Approach steep, open and/or sparsely treed slopes cautiously.
- Back off if you encounter whumpfing, hollow sounds, or shooting cracks.
- Investigate the bond of the recent snow before committing to your line.
Problems
Persistent Slabs
30 to 50 cm of recent snow has potential to form a persistent slab above weak layers. There have been reports of a poor bond to underlying sun crust layers on south slopes and surface hoar crystals on north slopes, especially north and south of Nelson in the Selkirk Range.
At this point we are uncertain about how long this problem will take to heal and suggest a more conservative approach to terrain to handle this uncertainty.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Wind Slabs
Expect to find freshly wind-loaded features to be reactive to human triggers as snowfall and southwest winds create wind slab in lee features in the alpine and treeline.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Mar 19th, 2022 4:00PM
