Avalanche Forecast
Issued: Dec 29th, 2023 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs, Loose Wet and Persistent Slabs.
mhalik,
Avalanche Canada
Kitimat, Nass, Rupert, Seven Sisters, Shames.
6:45 AM Update: Warm, stormy weather has increased the likelihood of triggering large, destructive avalanches.
Summary
Confidence
Moderate
Avalanche Summary
On Friday a MIN post described seeing several natural avalanches near the Anderson Cabin. Thursday a vehicle triggered a large avalanche in the alpine. It was reported to have failed 1 m deep on a layer of surface hoar. Wednesday two small rider-triggered avalanches and one large (size 2.5) naturally occurring slab were reported near Shames. With rain and warm temperatures in the forecast, we expect to see a spike in avalanche occurrences.
Snowpack Summary
Around 20 mm of rain is expected to saturate and overload the snowpack. 30-45 cm of heavy storm snow has bonded poorly to a slippery rain crust formed on Christmas. At upper elevations, strong winds from variable directions have likely built reactive slabs on many aspects in open areas and near ridge crests.Two buried surface hoar layers can still be found in isolated areas, buried 75-100 cm, and 120-200 cm deep. The remaining mid and lower snowpack contains several well-bonded crusts. Snow depths are highly variable depending on elevation, and decrease rapidly below treeline.
Weather Summary
Friday Night
Cloudy, moderate rain 5-8 mm is expected to mountain top, with the freezing level between 1800-2000 m. 30-50 km/h southerly winds and treeline temperatures around 2 °C.
Saturday
Cloudy, moderate to heavy rain 5-15 mm or 5-15 cm snow above 1500m. 20-35 km/h easterly winds, freezing levels between 1800-1400 m, and a high of 2 °C at treeline.
Sunday
Cloudy with no precipitation, 10-25 km/h southerly winds, freezing level dropping to 400 m, and high of -2 °C at treeline.
Monday
Cloudy with 3 cm of new snow, 10 km/h easterly winds, freezing level around 600 m, and a high of -2 °C at treeline.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Travel in alpine terrain is not recommended.
- Only the most simple non-avalanche terrain free of overhead hazard is appropriate at this time.
- Storm slabs in motion may step down to deeper layers resulting in large avalanches.
- Avoid avalanche terrain during periods of heavy rain.
Problems
Storm Slabs
30-45 cm of heavy storm snow is sitting over a slippery rain crust. It is likely to become over-stressed by added weight from forecast rain, resulting in potential for both human-triggered and natural avalanches.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Loose Wet
Loose wet avalanches will become increasingly likely at elevations where precipitation falls as rain.
Aspects: All aspects.
Elevations: Treeline, Below Treeline.
Likelihood
Expected Size
Persistent Slabs
Last week, large avalanches were running on layers of surface hoar that are now buried 75 - 200 cm deep. The rain will be a big test on the snowpack, potentially overloading these weak layers and resulting in large destructive avalanches.
Aspects: All aspects.
Elevations: Treeline, Below Treeline.
Likelihood
Expected Size
Valid until: Dec 30th, 2023 4:00PM
