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Avalanche Forecast

Archived

Jan 23rd, 2020–Jan 24th, 2020

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

Regions

South Coast.

Avalanche conditions will become increasingly dangerous as snow accumulates at lower elevations.

Confidence

Moderate - Uncertainty is due to rapidly fluctuating freezing levels.

Weather Forecast

THURSDAY NIGHT: Rain transitioning to snow as freezing level drops from 2000 to 1400 m, 30 mm of rain or potentially 20 cm of wet snow at treeline, strong wind from the south, treeline temperatures around +1 C.

FRIDAY: 10-20 cm of wet snow above 1000 m, rain below, moderate wind from the southwest, treeline temperatures around 0 C.

SATURDAY: Scattered rain showers and wet snow flurries with 5-15 cm of snow above 1000 m, light wind from the south, treeline temperatures around 0 C. 

SUNDAY: Brief clearing in the morning with treeline temperatures jumping to +3 C before temperatures drop and the next system arrives in the afternoon bringing heavy snow and wind.

Avalanche Summary

As heavy rain transitions to snow overnight expect thick storm slabs to form above treeline and a mix of storm slabs and wet loose avalanches at treeline and below treeline elevations. There is uncertainty about the amount of rain versus snow at each elevation band.

Snowpack Summary

Wet snow will begin to accumulate Friday morning as the freezing level drops. This snow will either create touchy wet loose or storm slab avalanches for the duration of the storm. Rain earlier in the week created a strong and settled snowpack, which is now 250-300 cm deep around the peaks of the North Shore mountains.

Terrain and Travel

  • Minimize exposure during periods of heavy loading from new snow, wind or rain.
  • Avoid terrain traps such as gullies and cliffs where the consequence of any avalanche could be serious.

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.