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Avalanche Forecast

Archived

Dec 25th, 2018–Dec 26th, 2018

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.

Variable amounts of snow are forecast for the region on Wednesday. Should enough fall, expect fresh wind slabs in the lees of terrain features.

Confidence

Moderate - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

TUESDAY NIGHT: Mostly cloudy with light snowfall, accumulation up to 5 cm, freezing level below valley bottom.WEDNESDAY: Cloudy with light snowfall, accumulation 5 to 10 cm, moderate southwest winds, alpine temperature -9 C, freezing level 500 m.THURSDAY: Mostly sunny, light northwest winds, treeline temperature -7 C, freezing level below valley bottom.FRIDAY: Increasing clouds over the day, light to moderate southwest winds, alpine temperature -5 C, freezing level below valley bottom.

Avalanche Summary

Cornices were reactive to explosive control on Monday. The cornice chunks did not pull slabs on the slopes below them. Otherwise, there was further evidence of a natural cycle from last weekend's storm.

Snowpack Summary

New snow on Wednesday should fall with strong southwest winds, possibly producing small wind slabs in the immediate lees of terrain features. Below 1800 m, storm snow from last weekend may not be bonding well to an underlying crust. See this MIN report for such an example. Otherwise, reports indicate that the recent snow is bonding well to the snowpack. Also note that the recent storms have grown cornices, which are relatively large for this time of year.A weak layer of facets and surface hoar lies around 150 to 200 cm deep in the snowpack. There hasn't been reports of avalanches on this layer for over a week. That being said, this layer may still exist in isolated areas around treeline in some portions of the region.At the base of the snowpack, weak and sugary facets are found below an early-season melt-freeze crust. This weak layer has been the culprit for sporadic, very large avalanches in alpine terrain in the past few weeks. The avalanches have occurred in areas where the ground roughness is very smooth, for example glaciers, firn, and shale/rock slab slopes. An avalanche could be triggered in this layer with a very large trigger, such as a cornice fall.

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.