Avalanche Forecast
Issued: Mar 8th, 2020 5:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Persistent Slabs.
MBender,
Avalanche Canada
A stable weather pattern with little precipitation is expected on Monday. Should the sun pop out, it could destabilize sun-exposed slopes and weaken cornices.
Summary
Confidence
High - Confidence is due to a stable weather pattern with little change expected.
Weather Forecast
SUNDAY Night: Clear periods, light southwest wind, alpine temperature -8 C.
MONDAY: Mix of sun and cloud, light west wind, alpine temperature -7 C, freezing level 900 m.
TUESDAY: Cloudy with snowfall, accumulation 5 to 10 cm, moderate southwest wind, alpine temperature -5 C, freezing level 1000 m.
WEDNESDAY: Mainly cloudy with scattered flurries, light west winds, alpine temperature -5 C, freezing level 1100 m.
Avalanche Summary
Reports on Sunday show two natural cornice failures to size 2 on north aspects in the alpine. On Friday, storm snow was reactive to riders and explosives. Many small to large (size 1 to 2.5) avalanches were triggered, generally 20 to 50 cm deep. There was also a report of a large conrice failure near Whistler, showcased in this MIN.
Snowpack Summary
25 to 35 cm of snow that fell late last week with strong to extreme south to southwest wind, formed wind slabs in lee terrain features at treeline and alpine elevations.
A weak layer of surface hoar crystals and/or faceted grains may be found around 100 cm deep on northerly aspects at treeline and lower alpine elevations. For some of the region, the layer may have been destroyed by strong wind immediately before burial on February 22nd, but it may still exist in sheltered terrain features in parts of the region. 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.
Weak faceted snow and melt-freeze crusts exist near the base of the snowpack in some of the region, particularly the eastern and northern parts. This layer is considered dormant, as it hasn't produced an avalanche since February 20th. This layer may require a very large load, such as a cornice fall, or rapid weather changes to reactivate it.
Terrain and Travel
- Carefully evaluate steep lines for wind slabs.
- Pay attention to cornices and give them a wide berth when traveling on or below ridges.
- Minimize exposure to sun-exposed slopes when the solar radiation is strong.
- Surface hoar distribution is highly variable. Avoid generalizing your observations.
Problems
Wind Slabs
25 to 35 cm of snow from Thursday fell with strong to extreme southeast to southwest wind, forming thick wind slabs in lee (northerly) terrain features. Also note that cornices are large and could fail from the weight of a human.
Aspects: North, North East, East, South East.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
A weak layer of feathery surface hoar may be found around 100 cm deep on northerly aspects around treeline and lower alpine elevations. This layer may be spotty and only found in sheltered terrain features in parts of the region. Although we haven't heard of any reports of avalanche activity on this layer for over a week, the layer has produced results in snowpack tests, where it exists. Assess the layer in the snowpack prior to committing to 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 9th, 2020 5:00PM
