Avalanche Forecast
Issued: Jan 21st, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Persistent Slabs.
astclair,
Avalanche Canada
Triggering avalanches may be possible in specific areas with stiff, wind-drifted snow or with a buried weak layer. Monitor for these conditions where you travel on Friday.
Summary
Confidence
Weather Forecast
Thursday night: Mostly clear, light northwest winds, alpine temperatures dropping to -20 C.
Friday: Mainly sunny, light northwest winds, alpine high temperatures near -14 C.
Saturday: Partly cloudy, light variable winds, alpine high temperatures near -15 C.
Sunday: Increasing cloud, light south winds, alpine high temperatures near -12 C.
Avalanche Summary
Recent strong winds have formed wind slabs in lee features at upper elevations that may be possible to human trigger. With the strong winds on Tuesday, operators in the region reported small to large (size 1-2) wind slabs releasing naturally as well as several size 1-2 explosive-triggered cornices.
On Monday and Tuesday, several operators in the region reported small (size 1-1.5) human-triggered avalanches releasing on a weak layer of surface hoar on north, east and southeast aspects at treeline and below treeline elevations. These avalanches were breaking 25-45 cm deep.
Snowpack Summary
Recent winds have scoured snow surfaces, loaded cornices, and formed stiff wind slabs in alpine and upper treeline areas. These wind slabs sit over a variety of surfaces, including isolated surface hoar, sun crusts, and settling storm snow. A new sun crust may be forming on steep solar aspects, and there here have been reports of surface hoar growing on the snow surface.
50-70 cm of snow from the past week has buried a weak of layer of surface hoar that is likely to be preserved in sheltered, open slopes at and below treeline. Observers in the south of the region continue to report sudden results in the snowpack tests and shooting cracks on this layer. Don't let benign weather lure you into complacency. Recent avalanche activity demonstrates that this layer is likely to be reactive where it is preserved and that it warrants careful assessment. Below 1700 m, 20-30 cm of snow is settling above a decomposing melt freeze crust.
Deeper in the snowpack, a couple of older persistent weak layers may still be identifiable from late and early December, consisting of surface hoar and a crust with faceted snow and buried anywhere from 100-200 cm deep. Prolonged periods of inactivity and unreactive snowpack test results suggest that these layers have trended towards dormancy.
Terrain and Travel
- Carefully evaluate steep lines for wind slabs.
- Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
- Avoid exposure to slopes that have cornices overhead.
Problems
Wind Slabs
Strong winds have redistributed recent snow into hard wind slabs on lee features at upper elevations that may be possible trigger. Cornices are adjusting to a rapid load and may trigger avalanches on the slopes below.
Aspects: North, North East, East, South East, South, West, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
A weak layer of surface hoar buried Jan 11 may be possible to trigger on open, sheltered slopes near and below treeline. This weak layer can be found buried 50-70 cm deep. Recent avalanche activity demonstrates that this layer is likely to be reactive where it has been preserved. Activity has been specific to the southern half of the region.
Aspects: All aspects.
Elevations: Treeline, Below Treeline.
Likelihood
Expected Size
Valid until: Jan 22nd, 2021 4:00PM
