Avalanche Forecast

Issued: Mar 28th, 2013 10:18AM

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

swerner, Avalanche Canada

South Rockies.

Summary

Confidence

Fair - Timing or intensity of solar radiation is uncertain

Weather Forecast

The region will be under a fairly dry NW flow. A mix of sun and cloud with possible light precipitation amounts Friday afternoon. Spring-like conditions persist through the weekend with clear, sunny, warm temperatures during the day and slight cooling overnight. Alpine temperatures are expected to reach around zero degrees and little wind is forecast.Friday: Scattered cloud. Alpine temperatures reaching 0.0 degrees. Freezing levels rising to 2500 m in the afternoon then dropping 1300 m overnight. Ridgetop winds will blow light from the West.Saturday: Few clouds. Alpine temperatures reaching 0.0 degrees. Freezing levels rising to 2600 m in the afternoon then dropping to 1500 m overnight. Ridgetop winds blowing light from the West.Sunday: Mostly sunny. Alpine temperatures -6.0. Freezing levels 1700 m and then falling to valley bottom overnight.

Avalanche Summary

On Thursday, several loose wet avalanches size 1 initiated from steep Southerly terrain.

Snowpack Summary

Cornices are large and will likely become weak due to strong solar radiation and warming temperatures. The surface snow has become moist or wet up to 2200 m, especially on solar aspects. Melt-freeze conditions exist. Wind slabs exist in the immediate lee of ridge lines and terrain features. Surface hoar and surface facetting is forming on sheltered, northerly aspects, especially at higher elevations. Approximately 40-70 cm of settling storm snow sits on top of a buried rain crust down 50 cm and exists up to around 2100 m. The bond of this snow to the crust has shown variability though the region. It is important to dig down and test weak layers before dropping into your line. A large trigger such as a cornice fall or a skier/sledder hitting the sweet spot, could potentially trigger a large avalanche on this layer.

Problems

Cornices

Large looming cornices exist on most ridgelines. Cornices may become weak under the influence of the sun. They are a hazard in themselves and they could trigger slopes below.

Give cornices a wide berth when travelling on or below ridges.>Avoid areas with overhead hazard.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 5

Loose Wet

Warmer afternoon temperatures and sunshine may promote deterioration within the upper snowpack. If surface snow becomes moist or wet, loose wet avalanches are likely. Watch solar aspects.

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 - 4

Wind Slabs

Wind loaded and cross-loaded slopes can still be found at treeline and alpine elevations. A small wind slab avalanche could step down to the March 16th rain crust. Wind slabs may be triggered under the weight of a skier, rider or cornice fall.

Whumpfing is direct evidence of a buried instability.>Use extra caution if planning to ride lee and cross-loaded terrain near ridge crests.>Plan escape routes and identify safe zones before committing to your line.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 4

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