Avalanche Forecast
Issued: Mar 22nd, 2022 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs, Loose Wet and Wind Slabs.
zryan,
Avalanche Canada
Avalanche danger will increase during periods of strong solar radiation or rain at lower elevations.
Head out with a conservative mindset and dial back your terrain choices until the weather cools.
Summary
Confidence
Moderate - Uncertainty is due to difficult to forecast freezing levels.
Weather Forecast
TUESDAY NIGHT: Cloudy. Moderate to strong southwesterly winds. Freezing level around 2500 m.
WEDNESDAY: Cloudy with light precipitation. Moderate to strong southwesterly winds. Freezing level around 2500 m.
THURSDAY: Clear in the morning with increasing cloud cover. Light variable winds. Freezing level around 1700 m.
FRIDAY: Partially cloudy. Light southwest winds. Freezing level around 1700 m.
Avalanche Summary
A few natural and human-triggered wind slabs occurred in the alpine and treeline on Monday (size 1-2).Â
There have been some notable human-triggered avalanches in Kootenay Pass and the Nelson area in the past week. These large slab avalanches (size 2), failed on either a buried sun crust on solar aspects or surface hoar on shaded aspects. This MIN report from an incident on Saturday near Whitewater is an example of this problem.Â
On Friday, an operator south of Nelson reported a large slab avalanche (size 3), triggered by a helicopter landing initiating a cornice failure. This avalanche stepped down to a deeper weak layer in the upper snowpack, suggesting that these deeper layers are still possible to trigger with large loads.
Snowpack Summary
50 to 70 cm of settling storm snow exists at higher elevations. New snow depths taper significantly with elevation, with moist and crusty surfaces below 1800 m and on south aspects into the alpine.Â
Last week's storm snow is bonding poorly to underlying layers in some areas. In the Selkirks, especially north of Nelson, it appears that this snow is bonding poorly to the underlying sun crusts on solar aspects and surface hoar on shaded aspects. In the Monashees, reports suggest that this snow has formed a stronger bond to underlying crusts. Several other crust layers are found 50 to 100 cm deep, and the snow is mostly well bonded to these crusts.
Terrain and Travel
- The more the snowpack warms-up and weakens, the more conservative you`ll want to be with your terrain selection.
- Minimize overhead exposure; avalanches triggered by warming or cornice fall may be large and destructive.
- Be aware of the potential for large avalanches due to the presence of a persistent slab.
- Avoid steep slopes when air temperatures are warm, it is raining, or solar radiation is strong.
- Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
Problems
Persistent Slabs
Last week's 30 to 60 cm of storm snow has formed a persistent slab above weak layers in some areas. This is a concern where there is a poor bond to underlying sun crust layers on south-facing slopes and surface hoar crystals on north-facing slopes. This problem seems most pronounced in the Selkirks around Nelson and around Kootenay Pass. (read more in this blog).
Several other crust/facet layers exist in the upper 100 cm of the snowpack. Human-triggered avalanches on these layers are unlikely, but large triggers such as a cornice failure, or a smaller avalanche stepping down to these layers is possible. Be extra cautious during periods of rapid loading, significant warming, or strong solar radiation.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Loose Wet
At lower elevations, the upper snowpack will likely stay wet and uncohosive with warm temperatures and cloud cover overnight. Wet loose avalanches will be possible out of steep terrain, especially if it rains at lower elevations on Wednesday.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Wind Slabs
Westerly winds are expected to continue redistributing available snow into wind slabs in lee features in the alpine and treeline.
Cornices have grown significantly in the past two weeks. Warm temperatures may make cause cornices to become weak. Cornice failures are dangerous on their own, but also have the potential to trigger larger avalanches on the slopes below.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Mar 23rd, 2022 4:00PM
