Archived

Avalanche Forecast

Apr 12th, 2013–Apr 13th, 2013

Alpine

3: Considerable

The avalanche danger rating in the alpine will be considerable

Treeline

3: Considerable

The avalanche danger rating at treeline will be considerable

Below Treeline

2: Moderate

The avalanche danger rating below treeline will be moderate

Alpine

2: Moderate

The avalanche danger rating in the alpine will be moderate

Treeline

2: Moderate

The avalanche danger rating at treeline will be moderate

Below Treeline

1: Low

The avalanche danger rating below treeline will be low

Alpine

2: Moderate

The avalanche danger rating in the alpine will be moderate

Treeline

2: Moderate

The avalanche danger rating at treeline will be moderate

Below Treeline

1: Low

The avalanche danger rating below treeline will be low

Regions: Cariboos.

The intensity of Friday night's storm is uncertain. If snowfall amounts are higher than anticipated or if the storm persists throughout Saturday morning, the avalanche danger may be HIGH in the alpine.

Confidence

Fair - Intensity of incoming weather is uncertain on Friday

Weather Forecast

Overnight Friday and Saturday: Moderate snowfall on Friday night tapering to light snowfall on Saturday / Strong southwest winds switching to moderate and northwesterly / Freezing level at 1200mSunday: Trace amounts of snow with overcast skies / Moderate northeast winds / Freezing level at 1200mMonday: Mix of sun and cloud / Calm winds / Freezing level at 1200m

Avalanche Summary

Natural loose dry avalanches to size 2 ran within Wednesday's storm snow, and a size 2 wind slab was ski cut on a northeast alpine slope just below ridge crest. A size 2 natural slab avalanche was observed in a north facing gully feature at 2100m. The early April interface was the suspected culprit. Although recent snow may be gaining strength, I would expect another round of storm slab activity to occur in response to wind and snow forecast for Friday afternoon.

Snowpack Summary

At upper elevations moderate amounts of recent snow have been shifted into deeper windslabs by steady southwest winds. About 40-75cm below the surface you are likely to find a temperature/sun crust from early April's clear weather. At the same interface you may find a layer of spotty surface hoar on shaded alpine slopes above ~2400m. At lower elevations (below 1600m) rain has saturated the snowpack, and surfaces are either moist or refrozen (temperature depending).Recent snowfall combined with wind have made large cornices bigger and more likely to fail.

Avalanche Problems

Storm Slabs

Moderate snowfall and strong winds forecast for Friday night will create new storm/ wind slabs. Storm slabs will be particularly touchy in wind-affected terrain.

Stay off recent wind loaded areas until the slope has had a chance to stabilize.>Choose conservative lines and watch for clues of instability.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely - Very Likely

Expected Size: 1 - 4

Cornices

Ongoing wind and snowfall has added to size and fragility to existing cornices. Cornice falls may be destructive by themselves, and may also trigger large avalanches on the slope below.

Pay attention to overhead hazards like cornices.>

Aspects: North, North East, East, South East.

Elevations: Alpine.

Likelihood: Possible

Expected Size: 1 - 6