Avalanche Forecast

Issued: Mar 27th, 2013 9:54AM

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 on Thursday

Weather Forecast

An upper low pressure system will be responsible for light precipitation and extended cloud cover on Thursday. Thunderstorms are possible in the afternoon.Thursday: Mostly cloudy with some sunny breaks. Alpine temperatures near -1.0 degree. Freezing levels up to 2300 m in the afternoon then falling to 1300 m overnight. Ridgetop winds will blow light from the West.Friday: Few clouds. Alpine temperatures near 2.0. Freezing levels 2500 m and ridgetop winds light from the West.Saturday:Â Clear skies. Alpine temperatures -2.0 and freezing levels rising to 2200 m. Ridgetop winds light from the West.

Avalanche Summary

Numerous small, loose wet avalanches occurred on steep solar aspects.

Snowpack Summary

Cornices are large and will likely become weak due to strong solar radiation and warming temperatures. Recent wind slabs exist in the immediate lee of ridge lines and terrain features. The surface snow has become moist or wet up to 2200 m, especially on solar aspects. Melt-freeze conditions exist. Surface hoar and surface facetting is forming on sheltered, northerly aspects, especially at higher elevations.Â 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.>

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. There is still a chance a small wind slab avalanche could step down to the March 16th rain crust.

Whumpfing is direct evidence of a buried instability.>Extra caution required on lee and cross-loaded terrain near ridge crests.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 4

Valid until: Mar 28th, 2013 2:00PM