Avalanche Forecast

Issued: Apr 3rd, 2017 4:19PM

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

triley, Avalanche Canada

South Columbia.

Cornices may become weak and fall off naturally during the heat of the day. Storm slabs in the alpine may continue to be reactive to human triggers.

Summary

Confidence

Moderate - Timing or intensity of solar radiation is uncertain

Weather Forecast

Overnight: Variable cloud with light winds and freezing down to valley bottoms. Tuesday: Mix of sun and cloud with light to moderate southwest winds and daytime freezing up to 1500 metres. Wednesday: Overcast with a few cm of new snow in the afternoon. Moderate southwest winds and daytime freezing up to 1700 metres. Thursday: 3-5 cm of new snow above 1300 metres. Winds becoming light with a chance of sunny breaks in the afternoon.

Avalanche Summary

On Sunday natural cornice falls released up to size 2.5, and one pulled an unsupported slope resulting in a deep slab release. There were also several reports of skier controlled and accidentally triggered storm slabs up to size 1.0.

Snowpack Summary

10-30 cm of recent snow now overlies a crust below about 2100 metres (higher on solar aspects) and moist snow below about 1800 metres. Below the new snow interface, storms over the past week brought 40-60 cm of snow to the region. Several other crusts as well as moist snow are likely to exist within this storm snow, mainly at lower elevations and on solar aspects. Moderate to strong southwest winds during and since the storm formed wind slabs on leeward slopes as well as fragile cornices along ridgelines. 90-130 cm of accumulated snow now overlies a more widespread rain crust below 2000 m and sun crust on solar aspects at higher elevations. At higher elevations, the February weak layers are down 160 cm to over 2 metres and the deep mid-December facet layer and November rain crust both still linger near the bottom of the snowpack. These layers were active during a storm in mid-March and produced some very large avalanches. Occasional deep releases continue to be reported and these deeply buried weaknesses remain a serious concern as solar radiation and warming temperatures begin to penetrate the snowpack at increasingly higher elevations.

Problems

Storm Slabs

Recent snow and wind have formed storm slabs that may remain reactive to human triggering. This problem is more pronounced in wind affected areas at higher elevations, so be vigilant for signs of recent wind loading.

Be especially careful with wind loaded pockets near ridge crests and roll-overs.Minimize your exposure to sun exposed slopes.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

2 - 3

Persistent Slabs

A cornice fall or smaller slab avalanche could trigger large, destructive avalanches on deeply buried weak layers. The likelihood of this happening will increase as solar warming weakens unstable cornices and storm slabs over the course of the day.

Recognize and avoid runout zones.Cornices or smaller slab avalanches could step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 4

Loose Wet

A solid re-freeze is expected overnight down to valley bottoms. The sun is strong at this time of year, and may result in loose wet avalanches at lower elevations and on solar exposed aspects in the afternoon.

Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Apr 4th, 2017 2:00PM