Avalanche Forecast
Issued: Mar 5th, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Persistent Slabs.
mconlan,
Avalanche Canada
Slabs that formed on Thursday may take a bit more time to stabilize. Watch out on sun-exposed slopes during periods of intense sun. Cornices are expected to be large and weak.
Summary
Confidence
Moderate - Uncertainty is due to how buried persistent weak layers will react with the forecast incoming weather.
Weather Forecast
THURSDAY NIGHT: Cloudy with snowfall then clearing, accumulation 5 cm, moderate southwest wind, treeline temperature -4 C, freezing level 600 m.
FRIDAY: Mix of sun and cloud, light southwest wind, treeline temperature -5 C, freezing level 800 m.
SATURDAY: Early-morning snowfall then a mix of sun and cloud, accumulation 5 to 10 cm, light southwest wind, treeline temperature -5 C, freezing level 600 m.
SUNDAY: Mostly clear skies, light northwest wind, treeline temperature -4 C, freezing level 800 m.
Avalanche Summary
No new avalanches were observed on Wednesday. Although we do not yet have observations from Thursday, it is expected that many avalanches occurred within the storm snow and potentially the surface hoar layer described in the Snowpack Summary. Natural avalanche activity should quiet down on Friday, but human-triggering will remain likely.
Snowpack Summary
Thursday's storm dropped around 20 to 30 cm of snow across the region. The snow fell with strong south to southwest wind, forming wind slabs in lee terrain features.
In some of the region, around 50 to 80 cm of snow overlies a layer of surface hoar on north-facing aspects near and above treeline. The layer has been found to be reactive in snowpack tests, such as in this MIN and this MIN. This persistent weak layer warrants investigation and a conservative terrain-use strategy. Check out the latest forecaster blog that offers a deeper dive into these conditions.
The remainder of the snowpack is well-settled. The snowpack depth varies from around 300 to 400 cm at the peaks of the North Shore mountains (1400 m), tapering rapidly with elevation, with no snow below 700 m.Â
Terrain and Travel
- Continue to make conservative terrain choices while the storm snow settles and stabilizes.
- 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.
- Surface hoar distribution is highly variable. Avoid generalizing your observations.
- Minimize your exposure time below cornices.
Problems
Storm Slabs
Around 20 to 30 cm of recent snow has likely started to consolidate into a storm slab in sheltered terrain. In exposed terrain at higher elevations, the snow fell with strong south to west wind, forming wind slabs in lee terrain features. These slabs may remain touchy to human traffic on Friday. Sun-exposed slopes should be treated as suspect during periods of intense sun. Cornices have also likely grown large and could fail during sunny conditions or from the weight of a human.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
A weak layer of feathery surface hoar may be found around 50 to 80 cm deep on northerly aspects around treeline and lower alpine elevations. Although we haven't heard of recent avalanches on this layer, we have reports of the layer still standing out and releasing in snowpack tests. Assess the layer in the snowpack prior to entering committing avalanche terrain or adopt a conservative mindset to avoid the problem.
Aspects: North, North East, East, West, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Mar 6th, 2020 5:00PM
