Avalanche Forecast
Issued: Mar 18th, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Deep Persistent Slabs.
astclair,
Avalanche Canada
Wind slabs may still be found and deeper layers may still persist. Make observations and assess conditions continually as you travel.
Summary
Confidence
Moderate - Uncertainty is due to limitations in the field data.
Weather Forecast
Wednesday night:1 Partly cloudy, light east wind, alpine temperature -2 C, freezing level valley bottom.
Thursday: Mostly cloudy, isolated flurries with trace accumulations, light east wind, alpine temperature -7 C, freezing level 1400 m.
Friday: Mix of sun and cloud, light northwest wind, alpine temperature -6 C, freezing level 1700 m.
Saturday: Mostly clear, light southwest wind, alpine temperature -6 C, freezing level 1700 m.
Avalanche Summary
Over the past several days, avalanche activity was reported as natural loose wet avalanches (size 1-2.5) running in steep, sun-exposed terrain in the alpine. One large (size 2.5) cornice failed as a result of explosive mitigation.
On Monday, there was a report of a skier remotely triggering (from a distance) a large (size 2) deep persistent slab avalanche at 2600 m on a northwest aspect. The avalanche was triggered from a thin spot, was 40-80 cm deep and ran on depth hoar near the base of the snowpack.
The number of data sources for the region is diminishing as professional operators close. If you're out in the mountains, consider sharing your observations via the Mountain Information Network. Heightened diligence and conservative risk management is recommended at this time.
Snowpack Summary
Previous moderate to strong northeast and east wind redistributed snow and formed wind slabs that may remain possible to trigger in isolated areas. With recent sun and relatively warm temperatures, expect to find either moist surface snow or crust on slopes facing the sun. New snow from last week may sit on a weak surface hoar layer and a sun crust on steep solar aspects.Â
A weak layer of surface hoar buried February 22 may be found 50-100 cm deep. Sheltered north, northeast, and east facing slopes near treeline are the most likely locations to find this layer. The last reported avalanche activity on this layer occurred March 11th. There is a low likelihood of triggering an avalanche on this layer, but the consequences of doing so would be high. Read more about surface hoar on our forecaster blog.
Deeply buried facets lurk near the bottom of the snowpack. This layer has been responsible for sporadic deep persistent slab avalanches, usually triggered from shallow, rocky start zones.
Terrain and Travel
- If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
- Small avalanches can have serious consequences in extreme terrain. Carefully evaluate your line for wind slab hazard before you commit to it.
- Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
- Make observations and assess conditions continually as you travel.
Problems
Wind Slabs
Lingering windslabs from recent moderate to strong northeast winds may be still reactive to human triggers.
Aspects: South East, South, South West, West, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Deep Persistent Slabs
Weak faceted snow near the base of the snowpack continues to be a concern. Treat wind-scoured, rocky, shallow terrain as suspect and avoid big alpine slopes that are threatened by cornices overhead. Additionally a weak layer of surface hoar sits 50-100 cm deep, within the range for human-triggering.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Mar 19th, 2020 5:00PM
