Avalanche forecast

South Coast

Mar 12 – 13, 2017Avalanche Canada
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Avalanche danger

Tue
Wed
Alpine
4 · High
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

A warm storm will bring rain, snow, and a range of avalanche hazards on Monday. Be aware of hazards changing and increasing as you gain elevation.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely - Possible
    Size
    2–4
    Storm snow from the past week sits over a buried persistent weak layer and very large avalanches may still be possible in isolated alpine terrain. A supportive crust is likely to prevent human triggering this layer at lower elevations.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely
    Size
    1–2
    Another pulse of snow and wind over Sunday night and Monday will leave fresh storm slabs on the surface at higher elevations. Expect stability to deteriorate as you gain elevation and as snow continues to fall.

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    1–2
    A natural loose wet avalanche cycle has already occurred, but up to 50 mm of rain in the forecast will reawaken the potential for further loose wet avalanche activity at lower elevations on Monday.

Confidence

Moderate - Freezing levels are uncertain

Weather Forecast

Sunday night: Periods of snow bringing 20 cm of new snow to higher elevations. Rain below about 1000 metres. Moderate to strong southwest winds. Monday: Continuing snowfall with 30 cm accumulating at higher elevations. Rain below about 1300 metres. Moderate southwest winds. Freezing level rising to 1700 metres by afternoon. Alpine temperatures around 0. Tuesday: Flurries bringing 5 cm of new snow to alpine elevations and intensifying overnight. Rain below about 1400 metres. Light to moderate south winds increasing over the day. Freezing level to 1800 metres and rising overnight. Alpine temperatures around 0 to +1. Wednesday: Continuing flurries bringing up to 10 cm of new snow. Moderate to strong southwest wind. Freezing level dropping from 2000 metres to 700 metres over the day. Alpine temperatures around 0 to -1.

Avalanche Summary

No new avalanches have been reported, but it should be noted that stormy weather has been discouraging some backcountry travel and obscuring visibility into alpine terrain.Looking forward, expect a change in avalanche hazards as you transition to higher elevations. Thick, reactive storm slabs can be expected at higher elevations, which increases the need for awareness of overhead hazards. Heavy rain will increase danger from loose wet avalanches at lower elevations. Large persistent slab avalanches may also remain sensitive to human triggering or to smaller avalanches in isolated areas of the alpine.

Snowpack Summary

Up to 50 cm of new snow can be expected to accumulate into touchy storm slabs on the surface at higher elevations by Monday afternoon. Below the surface, last week's stormy weather brought 130-200 cm of recent snow to the South Coast mountains. Below all the recent storm snow, you'll find the late-February interface. This layer is composed of a sun crust on southerly aspects and surface hoar on shaded aspects. Our supportive surface crust is likely to prevent triggering this layer at treeline and below, but this interface may remain reactive at alpine elevations. Although triggering this layer may be unlikely, doing so would produce a very large and destructive avalanche. Substantial snowfall and warming in the forecast are two factors that may promote reactivity at this interface on Monday. Below this interface, the mid and lower snowpack appear to be well settled and strong.

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