Avalanche forecast

Sea To Sky

Jan 20 – 21, 2016Avalanche Canada
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Avalanche danger

Fri
Sat
Alpine
5 · Extreme
Treeline
5 · Extreme
Below
4 · High
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Highlights

Conditions are ripe for an impressive avalanche cycle. Thursday is a day to wait out the storm from a safe place.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely - Certain
    Size
    2–6
    Buried surface hoar, down 60-100 cm, has been particularly touchy on shady aspects near treeline. Heavy loading will likely cause widespread natural avalanche activity on this interface on Thursday. 

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely - Certain
    Size
    1–5
    Stormy weather on Thursday will cause new storm and wind slabs to form. These may release naturally during the storm and may overload buried persistent weak layers. Expect widespread loose wet activity below treeline.

Confidence

High

Weather Forecast

Tonight and Thursday: 50-90 cm of snow. The freezing level starts near 1000 m and rises to 1600-2000 m late in the day. Winds are strong from the South. Friday: A few flurries and a clearing trend. The freezing level dips slightly to 1500 m. Winds ease to light from the SW. Saturday: Cloudy with sunny breaks. The freezing level is around 1200 m and winds remain light from the W-SW.

Avalanche Summary

All signs point to a snowpack that is primed for a large and widespread avalanche cycle with the incoming "Pineapple Express Light" storm arriving on Wednesday night. Reports from the last few days include numerous natural and rider-triggered slabs up to size 2. Many of these were failing on a surface hoar layer down 40-100 cm deep, and most occurred on Northerly aspects near treeline. Many public observers are also noting signs of instability like whumpfing and cracking.

Snowpack Summary

Approximately 60-100cm of storm snow has accumulated in the last two weeks and is bonding poorly to a widespread layer of surface hoar, facets, and/or sun crust from early January. Recent snowpack tests produced clean and sudden fractures on both these weaknesses with only moderate force. Expect this layer to become very active with intense loading this week! The mid and lower snowpack is generally strong, with the exception of shallower snowpack areas that may be more faceted. At lower treeline elevations recent rains have saturated the upper snowpack. At higher elevations moderate to strong southwest winds have recently loaded lee features at treeline and in the alpine.

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