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Avalanche Forecast

Archived

Mar 8th, 2020–Mar 9th, 2020

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

Sea To Sky.

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.

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

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.