Avalanche Forecast

Issued: Mar 16th, 2015 9:19AM

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

swerner, Avalanche Canada

South Columbia.

Strong solar radiation on Tuesday will likely trigger newly formed storm slabs and loose wet avalanches, especially in southern parts of the region. Be conservative in terrain selection and watch for changing conditions throughout the day.

Summary

Confidence

Fair - Timing or intensity of solar radiation is uncertain

Weather Forecast

On Tuesday, conditions will remain sunny and dry. A weak front will move onto the coast bringing generally light precipitation to Interior regions later Tuesday night. Ridgetop winds will blow light-moderate from the E-SE. Freezing levels will range from 1500-1800 m. Wednesday will see mainly cloudy skies with light convective precipitation which will continue through mid-day. Ridgetop winds will be light from the NW and freezing levels near 1700 m. Later Thursday, a strong front will approach the Coast and start to move inland bringing precipitation amounts to the Interior regions anywhere from 2-10 mm. Ridgetop winds will be strong from the SW and freezing levels will hover around 2000 m.

Avalanche Summary

On Sunday, reports of numerous size 1-3 natural slab avalanches and skier remote avalanches have been observed. Many of these larger events started as wind and storm slab avalanches from upper elevations. These avalanches have occurred on a variety of aspects with northerly aspects being most reactive. These have initiated from 2000-2800 m in elevation. With forecast sunshine and solar radiation, touchy slab avalanches are expected in the alpine and loose wet sluffing is possible from steep solar slopes at all elevations. 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, 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. In the alpine, strong winds during the storm are redistributing the new snow into wind slabs in leeward terrain features. Prior to the storm, 10-30cm of snow was sitting over a weak facet/crust layer that was buried in mid-February. 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 but now have the potential to wake-up with the current warm temperatures and new loading. A basal weakness has recently become active with the warm conditions and several avalanches have released to the ground.

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.

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

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 4

Loose Wet

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

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

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 3

Valid until: Mar 17th, 2015 2:00PM