Avalanche Forecast
Issued: Nov 25th, 2022 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs.
cgarritty,
Avalanche Canada
A reactive weak layer is in play in the upper snowpack and loading from the succession of storms is increasing its destructive potential. Make your interactions with avalanche terrain conscious and measured.
Summary
Confidence
Avalanche Summary
Many recent thin (15 cm) storm slab releases that failed on the mid-November interface were observed on Thursday in Glacier National Park.
A day earlier, many more signs of instability were noted elsewhere in the region, such as the Nelson area, Revelstoke, Sicamous, and very likely throughout the rest of the region.
The destructive potential of avalanches failing at this interface will be increased by Friday's snowfall.
Please share your observations to the MIN!
Snowpack Summary
10-25 cm of new is expected to cover the region by end of day on Friday with timing that progresses from north to south. The north can also expect the greatest accumulations.
The new snow adds to 15 to 30 cm of snow from Tuesday's storm that has been wind affected in exposed terrain but remains low density where sheltered.
This 25-50 cm of new and recent snow collectively overlies a variety of surfaces that formed mid-November, including weak surface hoar in sheltered treeline terrain, sugary faceted grains, a thin sun crust on steep solar aspects, or bare ground in wind-exposed terrain.
We can still only guess at the reactivity at this variable interface since the added load from Friday's storm, but the greatest concern may be where surface hoar is present (think sheltered, shaded areas).
Average snowfall depths are around 20 to 50 cm below treeline and 80 to 120 cm in the alpine.
Weather Summary
Friday night
Clearing with flurries diminishing. First in the north of the region in the afternoon, early evening in the south of the region. Winds easing to light west or northwest.
Saturday
15-25 cm of new snow from the previous 24 hours. Cloudy with flurries bringing about 5 cm more new snow in the afternoon or evening, starting in the north and increasing overnight. Light to moderate southwest winds, increasing over the day and overnight. Treeline high temperatures around -7 C.
Sunday
Mainly cloudy with continuing scattered flurries bringing 10-20 cm of new snow, including overnight amounts. Light to moderate west or southwest winds, easing over the day. Treeline high temperatures around -8 C.
Monday
Mainly sunny. Light east or northeast winds. Treeline high temperatures around - 10 C.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Closely monitor how the new snow is bonding to the old surface.
- Make observations and assess conditions continually as you travel.
- Be aware of the potential for larger than expected storm slabs due to the presence of buried surface hoar.
Problems
Storm Slabs
Recent storm snow has been accumulating and settling into slabs over a variable interface that has produced many avalanches and signs of instability since it was buried. By Friday evening it may be buried 50 or more cm deep in some areas and capable of producing large, destructive avalanches.
Avalanche hazard is unlikely anywhere snowpack depths have yet to overcome ground roughness like brush, trees, and rocks.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Nov 26th, 2022 4:00PM
