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Avalanche Forecast

Archived

Mar 3rd, 2020–Mar 4th, 2020

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

Regions

South Coast Inland.

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.

Confidence

Moderate - Forecast snowfall amounts are uncertain.

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

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.