Avalanche Forecast
Issued: Jan 4th, 2023 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs and Wind Slabs.
wlewis,
Avalanche Canada
Danger remains elevated as buried weak layers continue to produce large and unnerving avalanches. Stick to small and supported terrain features. Be cautious of areas where the snowpack depth changes rapidly, such as thin and rocky start zones.
Remember that small avalanches may step down to deeper weak layers as southerly winds are expected to build fresh wind slabs.
Summary
Confidence
Moderate
Avalanche Summary
Numerous large to very large (size 2 to 3) avalanches have been naturally and human triggered over the last week, failing on the weak layers described in the Snowpack Summary, 70 to 200 cm deep. Activity was mostly reported between 1800 m and 2500 m elevation and on all aspects. Check out this recent MIN.
These avalanches continue to indicate that these buried weak layers remain reactive, and are capable of producing large consequential avalanches. Many of these human-triggered avalanches were a surprise to the individuals triggering them.
Please continue to share any observations or photos on the Mountain Information Network.
Snowpack Summary
30-50 cm of low density snow sits at the surface of the snowpack. As southerly winds increase expect wind slabs to build in north facing terrain. New wind slabs may sit over a layer of reactive surface hoar and or crust.
The upper snowpack is generally settled and bonded well, however buried weak layers continue to be a concern, with large and surprising (remote or accidental triggered) avalanche activity reported throughout the last week.
A weak layer of crust, facets and/or surface hoar buried just before Christmas is buried 40-70 cm deep. The lower snowpack is generally weak and facetted with a weak layer of large facets from mid November near the bottom.
Snowpack depths are roughly 150 to 200 cm at treeline.
Weather Summary
Wednesday Night
Increasing cloud with moderate southerly winds developing. No snowfall expected. Freezing level below valley bottom.
Thursday
Mostly cloudy with moderate to strong southerly winds. Freezing levels remain below 500 m, alpine highs of -7 °C expected. Scattered flurries possible
Friday
Mostly cloudy. Strong southerly winds ease back to moderate. Light snowfall brings up to 5 cm. Freezing levels peak around 800 m. Alpine highs of -4 °C.
Saturday
Mostly cloudy with moderate southerly winds. Scattered flurries continue. Freezing levels peak around 800 m. Alpine highs of -4 °C.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.
- Be mindful that deep instabilities are still present and have produced recent large avalanches.
- Choose simple, low-angle, well supported terrain without convexities.
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
Problems
Persistent Slabs
Two concerning layers are responsible for most of the recent large avalanche activity. A layer of surface hoar, facets and/or a crust from late December is buried 40 to 70 cm deep.
A layer of large and weak facets also sits near the base of the snowpack, buried in November. Recent avalanche activity has occurred on both of these layers, with many avalanches stepping down to the deeper facets.
Although widespread, both layers appear to be most reactive around treeline and lower alpine elevations, in terrain with shallow, variable snow depths.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Wind Slabs
Low density snow on the surface is available for southerly winds to redistribute into pockets of wind slab in north facing terrain.
Small avalanches in wind loaded features have the potential to step down to deeper weak layers creating larger then expected avalanches.
Aspects: North, North East, East, West, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Jan 5th, 2023 4:00PM
