Avalanche forecast

South Coast

Mar 30 – 31, 2016Avalanche Canada
View on map
Archived · expired 11 years ago

Avalanche danger

Fri
Sat
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
Open full map

Highlights

A special warning has been issued for the substantial warming and sun this week. Extra caution is required around and below cornices, and on steep sun exposed slopes during the heat of the day.  Deep persistent avalanches may also become possible.

Avalanche problems

  • Cornices

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    1–5
    Large cornices are expected to get weak with warming and sun exposure, and natural cornice releases are possible in the afternoon. They can be destructive by themselves, and may also become the trigger for a slab avalanche on the slope below.

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely - Very Likely
    Size
    1–4
    Loose wet sluffing is expected on sun exposed slopes during the heat of the afternoon. Very high freezing levels may increase the size and run length of natural sluffing.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely - Possible
    Size
    3–6
    There is concern that buried weak layers may wake-up with the warming this week, especially in the northern half of the region. Pros are tracking a crust down 40cm and a facet layer down 120cm.  Very large avalanche may be possible in isolated areas.

Confidence

Moderate

Weather Forecast

The ridge of high pressure is expected to persist until Saturday morning. Thursday and Friday should be sunny with light alpine wind from the northwest and afternoon freezing levels above 3000m. Increasing cloud cover is expected on Saturday with moderate alpine wind from the southwest and freezing levels dropping below 2000m. Light scattered flurries are possible Saturday afternoon.

Avalanche Summary

On Tuesday, widespread natural loose wet sluffing was reported on solar aspects up to size 2.5 A natural size 2 wind slab avalanche was also reported in large open icefield area caused by down flowing wind. Natural cornice failures up to size 2.5 were also observed. On Monday, skier triggered avalanches up to size 1.5 were reported. The recent storm snow overlying a melt-freeze crust was reactive to triggering in wind affected terrain. Loose sluffing was also reported from steep southerly slopes. On Thursday, continued warming, sun exposure, and limited overnight recovery means natural cornice releases and loose sluffing are expected to continue.  As the warm temperatures continue, deep persistent weak layers have the potential to become reactive and produce very large slab avalanches.

Snowpack Summary

A moist snow surface is reported to be widespread to mountaintops except for shaded true north aspects at the highest elevations. Warm overnight temperatures means there was a limited refreeze of the snow surface. A thin crust may have formed in some areas but is expected to quickly break down in the morning. Wind affected surfaces are reported in exposed alpine terrain in response to recently strong northerly winds. Large cornices are lingering and are expected to become very weak with the sustained warming this week. Below the snow surface, there are two layers of concern in the northern half of the region. Professionals are tracking a melt freeze crust down around 40cm and a thick layer of facets down 120cm. As the snowpack continues to heat up this week, these layers have the potential to wake-up and produce very large avalanches.

Regions covered