Avalanche Forecast

Issued: Apr 3rd, 2013 10:01AM

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

mbender, Avalanche Canada

Purcells.

Be alert to conditions that change with daytime warming. Danger ratings are likely to exceed posted levels if solar radiation is strong, especially at treeline and below.

Summary

Confidence

Fair - Freezing levels are uncertain for the entire period

Weather Forecast

Thursday: A weak high pressure system builds promoting clear and dry conditions with light westerly winds and 2000m freezing levels.Friday: An upper trough of low pressure will move over the Interior late Thursday through Friday bringing moderate to locally heavy precipitation. Freezing levels will be around 1900m. Winds light to moderate from the west.Saturday: Overcast with light precipitation possible. Winds light from the south.

Avalanche Summary

Numerous natural loose wet avalanches up to size 2.5 and one natural cornice fall size 2.5.

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. 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

Loose Wet

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

Avoid travelling on slopes which are becoming wet due to rain, warm temperatures, or sun.>Be alert to conditions that change with elevation.>

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

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 4

Cornices

Natural cornice falls are a concern during daytime warming. Cornices may also be triggered easily by traveling near them.

Extra caution needed around cornices with current conditions.>Pay attention to overhead hazards like cornices.>

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 5

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.>

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

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 6

Valid until: Apr 4th, 2013 2:00PM