Archived

Avalanche Forecast

Nov 23rd, 2013–Nov 24th, 2013

Alpine

3: Considerable

The avalanche danger rating in the alpine will be considerable

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

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: Purcells.

Forecasts are based on limited observations. Dig down, test weak layers and keep an eye on rising temperatures.

Confidence

Fair - Due to the number of field observations

Weather Forecast

High pressure will strengthen though the forecast period bringing strong inversions (warmer temperatures) at upper elevations. No precipitation expected.Sunday/ Monday: A mix of sun and cloud. Alpine temperatures 0 degrees. Freezing levels near 2500 m. Ridgetop winds from the NW. Tuesday: Mainly sunny. Alpine temperatures below 0 degrees. Freezing levels falling to 1300 m. Ridgetop winds will be light from the NW.

Avalanche Summary

No recent avalanches reported. Earlier in the week a widespread cycle up to size 3 occurred throughout the region. Many of these avalanches ran on the October crust/ facet combo near the base of the snowpack.

Snowpack Summary

The average snowpack depths at upper elevations are near a metre or more. Wind slab problems likely exist on lee slopes.A bigger concern deeper in the snowpack is a melt-freeze / rain crust that formed early October. This is generally found from 70-120 cm down, with facetted (sugary) crystals above and below that are bonded poorly. The crust/ facet combo may be more predominant on Northerly aspects and allow for wider propagations, especially in places that have smooth ground cover (glacier ice, grassy slopes, rock slabs etc.).Snowpack conditions may change and deteriorate as temperatures rise in the alpine.

Avalanche Problems

Wind Slabs

Recent winds have dominated alpine and treeline areas. Touchy wind slabs are likely found lee of terrain features.

Assess start zones carefully and use safe travel techniques.>Use caution in lee areas in the alpine and at treeline. Recent wind loading has created wind slabs.>

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

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 3

Persistent Slabs

Rider triggered slab avalanches are failing on a crust that sits 60-120 cm below the surface.

Dig down to find and test weak layers before committing to a line.>Be aware of the potential for large, avalanches due to the presence of buried crust/facet combo.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 2 - 4

Loose Wet

Surface snow may become moist and weak with warm alpine temperatures and sunshine. Small loose wet avalanches could trigger the persistent weak layer buried deeper in the snowpack.

Minimize exposure to sun exposed slopes when things warm up. Indicators are moist surface snow, sluffing from trees, cliffs and steep southerly slopes.>

Aspects: North, North East, East.

Elevations: Alpine.

Likelihood: Possible - Likely

Expected Size: 1 - 3