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Avalanche Forecast

Archived

Mar 23rd, 2020–Mar 24th, 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

Northwest Coastal.

There is uncertainty in the forecast due to a lack of data available at this time.

Confidence

Moderate - Uncertainty is due to the limited number of field observations.

Weather Forecast

MONDAY NIGHT: Clear in the north of the region and partly cloudy with isolated flurries in the south of the region, accumulation 1 to 3 cm, light northeast wind, alpine temperature -5 C.

TUESDAY: Mostly clear skies, moderate north wind, alpine temperature -7 C, freezing level 600 m.

WEDNESDAY: Clear skies, light to moderate northwest wind, alpine temperature -3 C, freezing level 1000 m.

THURSDAY: Cloudy with snowfall accumulation 5 to 10 cm, moderate to strong west wind, alpine temperature -5 C, freezing level 800 m.

Avalanche Summary

No new avalanches were observed on Monday from limited reports. Wind slab activity may increase with the new snow and strong wind.

Snowpack Summary

Around 10 to 15 cm of snow fell Sunday night in the south of the region with strong northwest switching to southeast wind, likely forming wind slabs in exposed terrain features. In the northern half of the region, the wind was also howling so new slabs may be found. These slabs likely sit on a melt-freeze crust on sun-exposed slopes and otherwise previously wind-affected snow, so the new slabs may take some time to bond to the snowpack.

A layer of surface hoar crystals is buried around 30 to 60 cm in sheltered areas at and below treeline.

An early-season layer of faceted grains and a melt-freeze crust may linger at the base of the snowpack. A large load, such as a cornice fall, has the potential of triggering it.

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Approach steep open slopes at and below treeline cautiously, buried surface hoar may exist.
  • Make conservative terrain choices and avoid overhead hazard.

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.