Avalanche forecast

Sea To Sky

Dec 25 – 26, 2018Avalanche Canada
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Avalanche danger

Thu
Fri
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Highlights

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

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2
    Snowfall on Wednesday with strong southwest winds may produce small but touchy wind slabs. These may sit on lingering slabs from the weekend. Below about 1800 m, the weekend's snow may not be bonding well to a crust.

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.

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