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Avalanche Forecast

Archived

Jan 19th, 2020–Jan 20th, 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 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 unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

Sea To Sky.

Observe the depth of new snow to determine the scale of the storm slab hazard in your area on Monday, but be conscious of very different conditions in overhead terrain. Significantly more new snow exists in the alpine and in areas closest to the coast.

Confidence

Moderate - Forecast snowfall amounts are uncertain.

Weather Forecast

Sunday night: Cloudy with continuing snowfall bringing 5-20 cm of new snow to treeline and alpine, increasing with elevation and proximity to the coast. Light rain below about 1700 metres. Strong southwest winds. Freezing level peaking at 2000 metres and descending again through the morning.

Monday: Cloudy with continuing snowfall bringing about 10-25 cm of new snow, increasing with elevation and proximity to the coast. Light to moderate south winds. Alpine high temperatures around -3 with freezing levels to 1400 metres.

Tuesday: Cloudy with increasing snowfall bringing 10-30 cm of new snow, increasing with elevation and proximity to the coast. Moderate to strong south winds. Alpine high temperatures around -5 with freezing levels to 1200 metres.

Wednesday: Cloudy with isolated flurries. Light southeast winds. Alpine high temperatures around -5 with freezing levels to 1200 metres.

Avalanche Summary

Observations from the weekend storm are still limited, but initial reports from Saturday described touchy new slabs reacting easily to ski cuts on steeper features up to treeline on all aspects. Alpine elevations were largely avoided with visibility obscured. Fracture depths of up to 30 cm were observed.

Looking forward, continuing snowfall is expected to maintain similar conditions on Monday, with new snow and associated avalanche hazards increasing with elevation.

Snowpack Summary

5-20 cm of new snow, increasing with elevation, is expected to fall in the region by the end of the day Monday. This will cover rain-wetted surfaces below about 1700 metres and add to roughly 15-70 cm of snow from the weekend storm, again increasing with elevation and with proximity to the coast.

The storm buried recent wind slabs and wind-affected surfaces in exposed areas at all elevations and soft, low density snow in sheltered areas. It adds to just over a meter of storm snow that has fallen in the last week.

A pair of weak surface hoar layers from mid and late December existed about 70 to 160 cm below the surface in advance of the storm. These layers were given a good loading test at most elevations by the storm, but still warrant caution around steep, sheltered slopes and shallow rocky areas. 

A layer of sugary faceted grains and hard melt-freeze crust exists near the base of the snowpack in inland parts of the region, such as the Spearhead Range. This layer also received a good loading test by the storm, but continues to warrant avoidance of shallow rocky start zones in the alpine and upper treeline.

Terrain and Travel

  • Storm snow and wind is forming touchy slabs. Use caution in lee areas in the alpine and treeline.
  • Watch for unstable snow on specific terrain features, especially when the snow is moist or wet.
  • Remember that the snowpack will be significantly different at higher elevations than lower down.

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.

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.