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Avalanche Forecast

Archived

Mar 7th, 2022–Mar 8th, 2022

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 persistent slab problem requires diligence and a conservative mindset.

Confidence

High - Confidence is due to a stable weather pattern; little change is expected for several days.

Weather Forecast

MONDAY NIGHT: Cloudy with isolated flurries, trace accumulation, 10 km/h north wind, alpine temperature -4 C, freezing level 1300 m.

TUESDAY: Clear skies with no precipitation, 20 km/h north wind, alpine temperature -9 C.

WEDNESDAY: Clear skies with no precipitation, 10 km/h northeast wind, alpine temperature -13 C.

THURSDAY: Mix of sun and cloud with no precipitation, 10 km/h west wind, alpine temperature -8 C.

Avalanche Summary

The weekend saw various avalanche types, including some wind slabs at high elevations, many small wet loose avalanches, and a few persistent slab avalanches. The most concerning avalanches are the persistent slabs, which released on the weak layer described in the Snowpack Summary. The avalanches occurred on north to northeast aspects in alpine terrain. They avalanches propagated far, around 200 to 300 m.

Looking forward, it remains possible that persistent slab and wind slab avalanches could be triggered. Naturally-triggered avalanches may be on the decrease as the weather cools, but human triggering is possible.

Snowpack Summary

A dusting of snow sits on a surface melt-freeze crust on all aspects below around 1500 m and on sun-exposed slopes into the alpine. Dry snow remains on shaded slopes above around 1500 m. Recent northerly wind may form wind slabs in lee terrain features at higher elevations, which may rest on the crust.

Around 30 to 60 cm deep, a weak layer of sugary faceted grains may be found above a melt-freeze crust that formed in February. This layer has produced various human-triggered and natural avalanches over the past week. Activity has been most prevalent on northeast to northwest aspects at treeline and alpine elevations. Check out this forecaster blog for more info.

There are no deeper concerns at this time.

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Be aware of the potential for large avalanches due to the presence of a persistent slab.
  • Be aware of the potential for wide propagation.
  • Look for signs of instability: whumphing, hollow sounds, shooting cracks, and recent avalanches.

Problems

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.

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.