Avalanche Forecast
Issued: Jan 18th, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs, Persistent Slabs and Deep Persistent Slabs.
stephen holeczi,
Parks Canada
Windy and warm on Sunday which may cause a spike in natural activity. Limit exposure to overhead terrain while the winds are strong, and don't forget about the deeper weak layers when considering your terrain choices.
Summary
Weather Forecast
The big story is increasing temperatures Sunday (Alpine lows of -10 to -12C and highs of -2 to -4C), and continued strong winds in the alpine from the W/SW. Temperatures moderate on Monday with up to 10cm of snow Tuesday/Wednesday.
Snowpack Summary
2-15cm of new snow in the past 24 hrs (highest amounts on Hwy. 93N)and sustained Southerly winds continue to build wind slabs in the alpine and open areas at tree line. There is up to 60 cm above the Dec 31 layer of facets, surface hoar and sun crust. Concern remains for the weak layers of facets and depth hoar near the base of the snowpack.
Avalanche Summary
Numerous avalanche observations and reports yesterday across the region up to Sz 2.5. Natural cornice failures, wind and persistent slabs have come become reactive with the recent dramatic swing in temperatures. Local ski areas seeing smaller reactive wind slabs to size 2 in the alpine and treeline.
Confidence
Problems
Wind Slabs
Reactive wind slabs reported over the last 2 days which will likely continue with the warming temperatures and strong winds.
- Use caution in lee areas. Recent wind loading have created wind slabs.
- If triggered the wind slabs may step down to deeper layers resulting in large avalanches.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
This layer may present as surface hoar, facets or sun crust. It is buried 40-80cm throughout the region and produces variable results depending on location and what crystal form is present. There is high uncertainty as to how reactive this layer is.
- If triggered the persistent slab may step down to deeper layers resulting in large avalanches.
Aspects: All aspects.
Elevations: Treeline, Below Treeline.
Likelihood
Expected Size
Deep Persistent Slabs
Only large triggers like cornices have caused the odd slide on the deep facets/depth hoar recently, but it is almost impossible to forecast with any accuracy which avalanche slopes could be triggered. Conservative terrain choice is your best defence.
- Avoid shallow snowpack areas where triggering is more likely.
- Pay attention to overhead hazards like cornices which could trigger the deep persistent slab.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Jan 19th, 2020 4:00PM
