Avalanche Forecast

Issued: Mar 31st, 2013 9:29AM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is low. Known problems include Cornices, Loose Wet and Persistent Slabs.

mpeter, Avalanche Canada

Purcells.

Danger could INCREASE TO CONSIDERABLE with intense radiation on south and west aspects, especially at treeline and below. Be aware of how the warm weather is changing the snowpack.

Summary

Confidence

Good

Weather Forecast

Monday: One more warm day! Expect clear, sunny skies, light northwesterly winds and alpine temperatures to reach 2 with freezing levels at 2600.Tuesday/Wednesday: The ridge should begin to break down. Light/thin clouds are possible with temperatures slowly falling to more seasonal values. Expect light to moderate westerly winds. There is a slight chance of isolated flurries developing late on Wednesday.

Avalanche Summary

Numerous natural loose wet avalanches up to size 1.5 have been observed as well as one natural cornice fall size 2.5 that did not pulling a slab on the slope below.

Snowpack Summary

Surface faceting and surface hoar growth (up to 20 mm) has been prevalent on high, shady aspects, while the surface snow on sun-exposed slopes and at lower elevations (below 2000m) has been subject to daily melt-freeze cycles.Cornices are large and weak. Pockets of wind slab can be found on lee slopes and are possible to trigger under your skis or sled.A layer of buried surface hoar sitting on a crust down around 70-120cm, and has been producing variable results in snowpack tests. This persistent weakness remains a concern because of the potential for very large avalanches particularly with heavy triggers such as cornice falls. Old deep persistent weaknesses, including basal depth hoar, are a concern in shallow snowpack areas.

Problems

Cornices

Natural cornice falls are a concern during daytime warming. Cornices may also be triggered easily by traveling near them. Slopes with corniced entrances, or exposed to cornice falls should be avoided with these conditions.

Stay well back from cornices.>Be cautious of slopes that are exposed to cornices overhead.>

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 5

Loose Wet

Expect to see wet loose snow avalanches out of steep rocky sun-exposed slopes. Natural avalanche activity. snowballing, moist and wet snow surfaces are all initial indications of the upper snowpack deteriorating.

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

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

Elevations: All elevations.

Likelihood

Very Likely

Expected Size

1 - 4

Persistent Slabs

Small solar triggered slides, cornice fall, or thin-spot triggering may overload a persistent weakness buried 100 cm deep. This could lead to surprisingly large avalanches.

Be aware of thin areas that may propagate to deeper instabilites.>Carefully evaluate big terrain features by digging and testing on adjacent, safe slopes.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 6

Valid until: Apr 1st, 2013 2:00PM