Avalanche Forecast
Issued: Mar 3rd, 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
Snow and strong wind are forecast for Tuesday night, followed by a mix of sun and cloud. Slabs may be touchy on Wednesday. Treat the danger as HIGH if you find 30+ cm of snow accumulation, which could happen around the Coquihalla.
Summary
Confidence
Weather Forecast
TUESDAY NIGHT: Cloudy with snowfall, accumulation 10 to 15 cm and upward of 25 cm possible around Coquihalla, strong west wind, alpine temperature -10 C, freezing level 1100 m dropping to 500 m.
WEDNESDAY: Mix of sun and cloud, light to moderate west wind, alpine temperature -10 C, freezing level 900 m.
THURSDAY: Cloudy with snowfall, accumulation 5 to 10 cm, moderate to strong southwest wind, alpine temperature -6 C, freezing level 1400 m.
FRIDAY: Mix of sun and cloud with isolated flurries, accumulation 5 cm, light south wind, alpine temperature -10 C, freezing level 900 m.
Avalanche Summary
A few small wind slab avalanches were triggered by humans on Monday. They were small, on northerly aspects, and 10 to 20 cm thick.
Snowpack Summary
The next storm on Tuesday night will drop around 10 to 15 cm of snow for most of the region, though amounts upward of 25 cm are possible around Coquihalla. A mix of sun and cloud is then forecast for Wednesday. The snow may consolidate into a storm slab and it may moisten on sun-exposed slopes but stay dry on shaded slopes. The wind will be strong from the west during the storm, so expect wind slab development in lee terrain features, particularly near ridges.
A weak layer of surface hoar crystals and/or faceted grains may be found around 40 to 80 cm deep on northerly aspects at treeline and lower alpine elevations. The layer may have been destroyed by strong wind immediately before burial on February 22nd, but it may still exist in sheltered terrain features. Where it is found, it has been reactive in snowpack tests. 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.
In the northern part of the region (i.e., Duffey/Hurley/Goldbridge), a deep instability exists at the base of the snowpack. It has not produced an avalanche since February 17th. Rapid warming or heavy loading by new snow/wind/rain events have the potential to re-awaken this layer.
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.
- Avoid exposure to steep, sun exposed slopes, especially when the solar radiation is strong.
- If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
Problems
Storm Slabs
Variable snowfall amounts will accumulate across the region on Tuesday night, with amounts from 10 to 25 cm expected, and the most likely around Coquihalla. Both storm and wind slabs will rapidly develop during periods of intense snowfall and strong west wind. Use added caution if you find more than 25 cm of snow accumulate from the storm. Sunny periods on Wednesday could rapidly destabilize the snow on sun-exposed slopes.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
A weak layer of feathery surface hoar may be found around 40 to 80 cm deep on northerly aspects around treeline and lower alpine elevations. This layer may be spotty and only found in sheltered terrain features. Assess the layer in the snowpack prior to committing to avalanche terrain or adopt a conservative mindset to avoid the problem.
In the north of the region (e.g. Duffey, Hurley, Goldbridge), a deeper weak layer of faceted grains near the ground presents a lingering concern on steep, shallow slopes in the alpine.
Aspects: North, North East, East, West, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Mar 4th, 2020 5:00PM
