Avalanche Forecast

Issued: Mar 17th, 2015 9:09AM

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

swerner, Avalanche Canada

South Columbia.

Recently formed slabs remain sensitive to human triggering at higher elevations. Solar radiation and its destabilizing effect on the snowpack remains possible even if skies are cloudy.

Summary

Confidence

Fair - Timing or intensity of solar radiation is uncertain on Wednesday

Weather Forecast

The dry conditions and sunny skies are coming to an end as a series of pacific frontal systems hit the coast and bring cloudy skies and precipitation though the weekend. Wednesday will be fairly dry with a mix of sun and cloud. Ridgetop winds will be light-moderate from the West and freezing levels hover around 1800 m. Thursday will bring light snow amounts near 10 cm. Ridgetop winds will blow strong from the SW and freezing levels 1600-1800 m. Friday will remain cloudy with light precipitation 5-10 mm, and freezing levels rising to 2100 m.

Avalanche Summary

On Monday, reports of numerous size 1-2.5 natural slab avalanches and skier triggered avalanches have been observed. These avalanches have occurred on a variety of aspects with northerly aspects being most reactive. These have initiated from 2000-2600 m in elevation. A couple of these slab avalanches were triggered remotely from 50 m away an there is a still a concern for avalanches to step down to deeply buried weak layers resulting in larger persistent slab avalanches.

Snowpack Summary

At higher elevations, up to 20 cm of new snow sits over a plethora of surfaces including moist snow, crusts, wind affected surfaces, and/or old wind slabs which may still be reactive to rider triggering. Rain has soaked the upper snowpack to around treeline elevation forming a spring-like, melt-freeze crust. In the alpine, strong winds have redistributed the new snow into wind slabs in leeward terrain features. Prior to the storm, 10-30 cm of snow was sitting over a weak facet/crust layer that was buried in mid-February. This interface has not been as reactive in the South like it has in the North; however, it still exists and should remain on your radar. The late-Jan crust/surface hoar layer (around 1m deep) and the mid-January surface hoar (around 1.5m deep) have been dormant for several weeks.

Problems

Storm Slabs

A new storm slab sits over a weakness from mid-February and is reactive to human-triggering. Thicker, touchy wind slabs can be found in leeward terrain features in wind exposed terrain.

Use conservative route selection, stick to moderate angled terrain with low consequence, storm slabs may take several days to stabilize.>Avoid freshly wind loaded features.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 4

Loose Wet

Solar radiation will likely deteriorate the upper snowpack initiating loose wet avalanches. Overhead hazards like cornices could also fail and trigger avalanches on the slopes below.

Pay attention to overhead hazards like cornices.>Watch changing conditions throughout the day in regards to aspect, elevation and timing of solar radiation, even if skies are a mix of cloud and sun.>Avoid sunny slopes when the solar radiation is strong, especially if snow is moist or wet.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 3

Valid until: Mar 18th, 2015 2:00PM