Avalanche Forecast

Issued: Mar 29th, 2013 9:52AM

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 increasing.

Summary

Confidence

Good

Weather Forecast

The region continues to be under a significant high pressure system with a blocking pattern. This pattern will not allow any active weather throughout the forecast period. Sunny skies with few clouds and unseasonable high freezing levels will continue.Saturday: Few clouds. Alpine temperatures near 5.0 and freezing levels rising to 2400 m. Ridgetop winds will blow light from the West.Sunday: Mostly sunny with possible high cloud. Alpine temperatures 5.0 degrees and freezing levels 2500 m. Ridgetop winds will be light from the NW.Monday: Mix of sun and cloud. Alpine temperatures near 2.0 degrees and freezing levels hover around 2200 m. Ridgetop winds blowing light from the West.

Avalanche Summary

Solar aspects have been very active showing loads of natural loose wet avalanches and cornice releases up to size 2.5. I expect natural avalanche activity to continue with freezing levels to the moon 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. Slopes with corniced entrances, or exposed to cornice falls should be avoided with these conditions.

Give cornices a wide berth when travelling on or below ridges.>Cornices become weak with daytime heating, so travel early on exposed slopes and be aware of your overhead hazards.>

Aspects: North, North East, East.

Elevations: Alpine.

Likelihood

Likely

Expected Size

2 - 6

Loose Wet

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

Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.>

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

Elevations: All elevations.

Likelihood

Very Likely

Expected Size

1 - 5

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.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 6

Valid until: Mar 30th, 2013 2:00PM