Archived

Avalanche Forecast

Mar 30th, 2013–Mar 31st, 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

2: Moderate

The avalanche danger rating below treeline will be moderate

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

Regions: Northwest Coastal.

Be alert to conditions that change with daytime warming. Danger ratings may exceed posted levels when solar radiation is strong.

Confidence

Good

Weather Forecast

Clear skies are expected on Sunday with increased cloud on Monday and a chance of light precipitation on Tuesday. Winds will be mostly light from the southwest increasing to moderate late Monday. Freezing levels may reach 2400m on Sunday, 1800m on Monday and then 1400m on Tuesday.

Avalanche Summary

In the far north of the region a cornice collapse triggered a size 3 slab avalanche which failed down to glacier ice. In recent days, natural slab avalanches up to 2.5 have been reported, likely failing on the March 9th layer. Several loose wet sluffs up to size 2.5 have also been reported. As well, a recent size 2.5 slab avalanche was remotely triggered by a skier in the Hidden Lake area near Shames. Once again, the March 9 surface hoar layer was the culprit. Nobody was caught in the slide. On Friday a skier-triggered size 1 slab occurred on a solar aspect on March 9th surface hoar. This avalanche remotely triggered a 2nd slab (150m away) lower down in a similar terrain feature again on the March 9th layer.

Snowpack Summary

Surface snow has settled with the influence of warm temperatures and surface hoar is growing on shaded slopes. Solar aspects and lower elevation terrain are now well into a daily melt-freeze cycle with sun-exposed slopes becoming very weak with daytime warming.Between 50-75cm below the surface is layer of surface hoar buried on March 9th which is variably reactive. In some areas it is stubborn and requires a significant trigger, while in other areas the layer is well preserved and primed for human triggering with the potential for very large avalanches. Check out the Forecaster's Blog for related discussion.The mid snowpack is generally well settled and strong. Having said that, basal facets may resurface as a concern with spring warming, particularly in the north of the region.Cornices are large and untrustworthy, especially when the sun is out.

Avalanche Problems

Persistent Slabs

In some areas the March 9th layer can be triggered from a distance, propagate across large distances and create surprisingly large avalanches.

Be aware of the potential for large avalanches due to the presence of buried surface hoar.>Avoid areas with overhead hazard.>Choose well supported terrain without convexities.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1 - 6

Loose Wet

Expect loose wet sluffs to fail on sun-exposed slopes.

Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>

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

Elevations: All elevations.

Likelihood: Likely - Very Likely

Expected Size: 1 - 5

Cornices

Large developed cornices loom over slopes. Forecast warming will increase the chances of failure with the potential to initiate large avalanches.

Cornices become weak with daytime heating, so travel early on exposed slopes.>Give cornices a wide berth when travelling on or below ridges.>

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

Elevations: Alpine.

Likelihood: Possible

Expected Size: 1 - 6