Avalanche Forecast
Issued: Mar 1st, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs and Wind Slabs.
ahanna,
Avalanche Canada
A weak layer rears its head as the overlying slab matures in the south of the region. Human triggered avalanches are very likely right now. Avoid sharp changes in terrain shape and keep in mind it's not always the first rider who triggers the slab.
Summary
Confidence
Moderate - Uncertainty is due to extremely variable snowpack conditions reported through the region.
Weather Forecast
Sunday night: Flurries bringing around 5 cm new snow. Moderate to strong northwest wind, extreme at ridgetop by early morning. Freezing level 700 m.
Monday: Flurries bringing around 5 cm new snow. Moderate west wind, strong at ridgetop. Freezing level 1000 m.
Tuesday: Flurries bringing 5-10 cm new snow. Moderate west wind. Freezing level 1500 m.
Wednesday: 5-10 cm new snow. Light west wind. Freezing level 900 m.
Avalanche Summary
On Friday and Saturday, skier triggered persistent slab avalanches size 1-2 were triggered on the surface hoar layer on north to east aspects around treeline. A size 3 natural was observed on an east aspect in the alpine. Check out this MIN report of how the high freezing levels on Friday impacted low and mid elevations.Â
Snowpack Summary
Recent wind has redistributed surface snow in the alpine and exposed treeline, loading snow into lee terrain features. Fresh wind slabs will continue to form as the wind picks up again Monday.
In the south of the region, a weak layer of widespread surface hoar sits 40-70 cm deep. On solar aspects it may sit on a sun crust which makes an excellent bed surface for avalanches. The overlying snow has been cohered into slabs by incremental loading through successive storms, wind at upper elevations and mild temperatures at lower elevations. As slab character increases, so do reactivity and size of avalanches failing on the weak layer (surface hoar). Read more about surface hoar on our forecaster blog! There is uncertainty about the distribution of this layer in the north of the region.Â
The mid and lower snowpack is generally well-settled and strong.
Terrain and Travel
- Stick to simple terrain or small features with limited consequence.
- Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Be aware of the potential for large avalanches due to the presence of buried surface hoar.
Problems
Persistent Slabs
A weak layer of surface hoar sits 40-70 cm deep. The overlying snow has been cohered into slabs by incremental loading through successive storms, wind at upper elevations and mild temperatures at lower elevations. As slab character increases, so do reactivity and size of avalanches failing on the weak layer (surface hoar). Read more about surface hoar on our forecaster blog!
Skier triggering of these persistent slabs is likely, and has be observed over the last few days even as professionals seek to actively avoid suspect terrain features (eg. convex rolls). Observations are concentrated on north to east aspects around treeline.
This problem has been observed mostly in the south of the region. There is uncertainty around the distribution of the surface hoar problem in the north.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Wind Slabs
Strong southwest wind has formed wind slabs in exposed terrain. Use added caution in lee terrain features, particularly near ridges.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Mar 2nd, 2020 5:00PM
