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Avalanche Forecast

Archived

Mar 3rd, 2020–Mar 4th, 2020

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

Regions

Sea To Sky.

Snowfall and strong wind Tuesday night, followed by sun and cloud on Wednesday. New slabs may remain touchy on Wednesday. Treat the hazard as HIGH if you find 30+ cm of snow accumulation.

Confidence

Moderate - Forecast snowfall amounts are uncertain.

Weather Forecast

TUESDAY NIGHT: Cloudy with snowfall, accumulation 15 to 30 cm, strong west wind, alpine temperature -10 C, freezing level 1000 m dropping to 500 m.

WEDNESDAY: Mix of sun and cloud, light west wind, alpine temperature -10 C, freezing level 900 m.

THURSDAY: Cloud with snowfall, accumulation 20 to 30 cm, strong southwest wind, alpine temperature -7 C, freezing level 1000 m.

FRIDAY: Morning snowfall then mix of sun and cloud with isolated flurries, accumulation 5 to 10 cm, light south wind, alpine temperature -10 C, freezing level 700 m.

Avalanche Summary

Small wind slabs were reactive to human traffic on Monday. Otherwise, no avalanches were observed.

The last reported avalanche on the surface hoar layer described in the Snowpack Summary was on February 26. However, snowpack tests suggest that this layer remains a concern where it exists in the region.

Snowpack Summary

The next storm on Tuesday night will drop anywhere from 15 to 30 cm of snow across the region, followed by some sunny skies on 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 50 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.

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.

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.
  • 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.

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.