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Avalanche Forecast

Archived

Jan 24th, 2020–Jan 25th, 2020

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

Regions

Northwest Coastal.

Continued snowfall with consistently strong southwesterly winds will maintain elevated avalanche danger Saturday. If 24 hour new snow amounts exceed 20 cm, increase the danger to high for exposed treeline and alpine areas.

Confidence

Moderate - Forecast precipitation (either snow or rain) amounts are uncertain.

Weather Forecast

Friday night: 5 -15 cm new snow. Strong southwesterly winds. Freezing level around 1000 m.

Saturday: 5-10 cm near Terrace, 30-40 cm near Kitimat. Strong southwesterly winds. Freezing level around 1000 m.

Sunday: 5-10 cm new snow. Moderate southwesterly winds. Freezing level around 800 m.

Monday: 10-15 cm near Terrace, 20-30 cm near Kitimat. Moderate southwesterly winds. Freezing level around 500 m.

Avalanche Summary

On Thursday, numerous loose wet avalanches to size 1.5 were observed in steep features below 700 m. Several natural and skier triggered storm slab avalanches up to size 1 were reported at treeline elevations. Few alpine observations due to limited visibility, but a few reports of natural wind slab avalanches up to size 2.5.

Reports of deep persistent slab avalanches have been trickling in throughout the month, with the last reported event occurring on Jan 17th. They are associated with a November crust layer near the base of the snowpack which has produced very large avalanches (size 3+) with crown depths of around 2 m. These have typically run in alpine terrain, on lee or cross-loaded slopes. Recent loading has been a good test for this layer and it seems to be trending less reactive.

Snowpack Summary

Around 1 m of recent storm snow is settling rapidly with mild weather, with moist surface snow below 1400 m. In exposed areas above 1400 m, expect southerly winds to build fresh wind slabs on north facing slopes. The new snow rests on extensively wind affected surfaces at upper elevations, and a thick layer of weak facets in sheltered areas treeline and below.

A deep crust from mid November lurks at the base of the snowpack. Although the last reported avalanche on this layer was from Jan 17th, I wouldn't write this layer off. At this time it is most likely to react in response to a large trigger such as a cornice fall, or in response to significant warming.

Terrain and Travel

  • Watch for rapidly changing conditions during periods of heavy loading from new snow, wind, or rain.
  • Storm snow and wind is forming touchy slabs. Use caution in lee areas in the alpine and treeline.
  • Be alert to conditions that change with elevation, aspect and exposure to wind.
  • The more the snow feels like a slurpy, the more likely loose wet avalanches will become.

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.

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.