Avalanche Forecast
Issued: Feb 20th, 2022 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Persistent Slabs.
zryan,
Avalanche Canada
Northeasterly outflow winds will redistribute the storm snow into fresh wind slabs in more atypical areas, which could take riders by surprise.
Avoid wind-loaded areas and carefully assess the bond of the new snow to the old surface.
Summary
Confidence
Weather Forecast
Bundle up in your warmest gear, arctic air is here!
Sunday Overnight: Clearing. Strong northeasterly winds. Alpine temperatures around -25 C.
Monday: Mainly clear. Strong northeasterly winds. Alpine temperatures around -25 C.
Tuesday: Cold and clear. Light to moderate northeasterly winds. Alpine temperatures around -20 C.
Wednesday: Mainly cloudy, light flurries. Light to moderate northwesterly winds. Alpine temperatures around -15 C.
Avalanche Summary
Limited observations have been made with poor visibility, but we expect a natural avalanche cycle occurred on Saturday. During the peak of the storm on Saturday, several large natural storm slab avalanches were reported from treeline elevations in the Kakwa.
On Thursday, operators in the Dezaiko range reported a skier-triggered storm slab avalanche on a northeast aspect in the alpine. This avalanche was remote-triggered, meaning the person was a distance away from where the slab initiated.
Snowpack Summary
An intense storm over the past 3 days brought 20-100 cm of new snow to the region, with lightest amounts in the Pine Pass area, and heaviest amounts in the southwest ranges around McBride. This new snow overlies a widespread crust created from a rain event in early February. This 1-20 cm thick crust exists on all aspects and elevations, excluding areas in the high alpine in the south of the region that may remain crust-free.
Below the crust, 10-40cm of more settled snow exists above the late January weak layer. This layer consists of weak faceted snow, a melt-freeze crust, and surface hoar crystals in isolated sheltered areas at treeline and below. The surface hoar has been increasingly hard to identify in the snowpack and has shown no reactivity in the past week. In many areas, this layer is bridged by the thick crust above it.
The lower snowpack is generally strong and well-bonded. The base of the snowpack is expected to be weak and faceted in shallow, rocky slopes east of the divide.
Terrain and Travel
- Continue to make conservative terrain choices while the storm snow settles and stabilizes.
- Recent wind has varied in direction so watch for wind slabs on all aspects.
- Closely monitor how the new snow is bonding to the crust.
- Look for signs of instability: whumphing, hollow sounds, shooting cracks, and recent avalanches.
Problems
Storm Slabs
Throughout the day today, northeasterly outflow winds may cause reverse loading, transporting available snow into fresh wind slabs in normally wind-scoured slopes.
With greater snowfall amount in the south, we can expect a more widespread storm slab problem to persist. 40-100cm of recent storm snow may bond poorly to the underlying hard melt-freeze crust. Expect deeper and stiffer slabs to exist in wind-loaded features.
In the north of the region, the problem is likely more confined to a wind slab problem. 10-30 cm of recent storm snow has been redistributed by southwest winds into wind slabs in lee areas.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
A weak layer formed by clear skies in late January exists in the upper meter of the snowpack. In most areas, a firm crust under the most recent storm snow will bridge the weak interface, making human triggering unlikely.
On the eastern side of the ranges in shallower snowpack areas, weak snow (basal facets) may exist near the base of the snowpack.
Large triggers, like warming, additional load from new snow, and cornice failures could be enough to wake these layers up, initiating large and surprising avalanches.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Feb 21st, 2022 4:00PM
