Avalanche Forecast

Issued: Mar 28th, 2013 11:00AM

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

swerner, Avalanche Canada

South Columbia.

The region will be under the influence of a major warm-up through the weekend. Be aware of snow conditions changing quickly and avalanche danger rising to CONSIDERABLE.

Summary

Confidence

Good

Weather Forecast

Spring-like conditions persist through the weekend with clear, sunny, and very warm temperatures during the day. We should see some cooling at night. Alpine temperatures are expected to reach above zero degrees and little wind is forecast.Friday: Few clouds. Alpine temperatures reaching 4.0 degrees. Freezing levels rising to 2200 m in the afternoon then dropping 700 m overnight. Ridgetop winds will blow light from the West.Saturday: Few clouds. Alpine temperatures reaching 5.0 degrees. Freezing levels rising to 2400 m in the afternoon then dropping to 1000 m overnight. Ridgetop winds blowing light from the West.Sunday: Sunny. Alpine temperatures -3.0. Freezing levels 1600 m and then falling to valley bottom overnight.

Avalanche Summary

Solar aspects have been very active showing loads of natural loose wet, dry and cornice releases. Cornice releases have been reported up to size 3, and not pulling out slab avalanches on the slopes below. Loose wet avalanches have been size 1-2.5 and predominantly from solar aspects at all elevations.I expect avalanche activity to continue with warming temperatures and sunny skies throughout the forecast period.

Snowpack Summary

Surface faceting and surface hoar growth ( up to 20 mm) has been prevalent on shady slopes and at upper elevations, while the surface snow on sun-exposed slopes and at lower elevations has been subject to daily melt-freeze cycles. Cornices are reported to be very large and weakly bonded. Cornice fall has been responsible for triggering some persistent weak layers below and initiating some very large avalanches.The weak layer of buried surface hoar from March 10th is down more than a metre in most places, and is giving variable results in snow profile tests. However, this deep persistent weakness remains a concern and may be triggered by larger loads or hitting the sweet spot in thin, variable snowpack areas. Wind slabs are reported to be strengthening, but may continue to be sensitive to human-triggers.

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.

Do not travel on slopes that are exposed to cornices overhead, especially during the heat of the day.>Extra caution needed around cornices with current conditions.>

Aspects: North, North East, East.

Elevations: Alpine.

Likelihood

Likely - Very Likely

Expected Size

2 - 6

Loose Wet

Periods of strong solar radiation may cause loose moist or wet snow avalanches. Keep an eye on changing conditions: Avalanche activity snowballing, moist and wet surface snow are initial indicators of deterioration and an increase in hazard.

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

Very Likely - Certain

Expected Size

1 - 4

Persistent Slabs

The March 10th weak layer of surface hoar is buried down more than a metre in most places. It may become more stressed with the weekend warm-up. Pockets of wind slab from localized wind, including down-flowing katabatic wind, may be rider triggered.

Be aware of thin areas that may propagate to deeper instabilites.>Dig down to find and test weak layers before committing to a line.>Plan escape routes and identify safe zones before committing to your line.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 6

Valid until: Mar 29th, 2013 2:00PM