Avalanche Forecast
Issued: Feb 17th, 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.
ghelgeson,
Avalanche Canada
Strong southwest wind is expected on Thursday which has the potential to quickly form touchy wind slabs. Seek out wind sheltered terrain, and please let us know what you're seeing if you're out tomorrow. Thanks!
Summary
Confidence
Weather Forecast
WEDNESDAY NIGHT: Freezing level at valley bottom, light west/northwest wind, no snow expected.
THURSDAY: A few clouds at dawn building to broken cloud cover in the afternoon, strong south/southwest wind, trace of snow possible during the day with 1 to 5 cm expected Thursday night.
FRIDAY: Overcast, freezing level rising to about 1000 m, moderate to strong west/southwest wind, trace of snow possible during the day with 1 to 5 cm Friday night.
SATURDAY: Broken cloud cover, freezing level beginning at valley bottom rising to about 900 m, strong southwest wind, trace of snow possible during the day with 5 to 10 cm Saturday Night.
Avalanche Summary
No new avalanche activity to report from this week.
Over the weekend, observers reported several small human-triggered wind slabs at treeline and alpine elevations in areas west in the region (see the MIN reports here and here). A MIN report near Valemount reported small loose dry avalanches on steep terrain in the trees.
Earlier in February, there was widespread avalanche activity on a weak layer of buried surface hoar, mostly on treeline features (see some photos in the MIN reports here, here, and here).
Snowpack Summary
Light flurries have begun to accumulate over a variety of surfaces including surgary facets, feathery surface hoar, and wind-affected snow that formed as a result of last week's dry, cold weather. New snow totals ranging from 10-15 cm may be found in areas west and north in the region, with 5 cm falling in the south and Strong southwest winds at ridgetop are expected to build fresh wind slabs that may be possible to trigger. Lingering wind slabs from last week's wind-loading events are trending unreactive.
40-70 cm of snow from February is settling over a reactive weak layer of surface hoar buried in late January. In some areas, there may be two of these layers in close proximity (buried Jan 24th and Jan 30th). Reactivity on these surface hoar layers has primarily been observed at treeline and in "treeline-like" features, like cutblocks, that are below treeline. On steep south-facing terrain, this layer may consist of facets on a sun crust.
Additional weak layers may present in the lower snowpack, but are not a concern in most areas until we see significant snow loading or rapid warming.
Terrain and Travel
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Wind slabs are most reactive during their formation.
- Be aware of the potential for large avalanches due to the presence of buried surface hoar.
- Extra caution is needed around cornices under the current conditions.
Problems
Wind Slabs
New snow totals vary across the region from 5-15 cm. Strong southwest wind Thursday is expected to form recent snow into fresh wind slabs which will come to rest on weak facets and surface hoar. This combination could make them surprisingly sensitive to human triggering. Cornices may be reaching their breaking point and can act as triggers on slopes below.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
A weak layer of surface hoar is buried 40-70 cm deep that may be possible to human trigger. This layer has been most sensitive around treeline, but may also extend into alpine terrain and/or down into the trees. In some areas, two layers of surface hoar are buried in close proximity, 30-70 cm deep.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Feb 18th, 2021 4:00PM
