Avalanche Forecast

Issued: Mar 3rd, 2018 5:16PM

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

ghelgeson, Avalanche Canada

South Coast Inland.

Up to 40 cm of fresh snow in the south of the region is hiding wind slabs that may still be sensitive to human triggering. Overcast skies and isolated flurries are expected to limit the effects of the strong late-winter sun on Sunday.

Summary

Confidence

Moderate - Timing or intensity of solar radiation is uncertain on Sunday

Weather Forecast

The forecast has changed since yesterday. Sunday looks to be cloudy with a chance of flurries for the South Coast Inland. Monday also looks cloudy, but clouds may give way to clear skies on Tuesday. SUNDAY: Overcast, freezing level rising to around 500 m, moderate west/southwest wind, 1 to 5 cm of snow possible.MONDAY: Scattered cloud cover in the morning, increasing cloud throughout the day, freezing level rising to around 800 m, light to moderate west/southwest wind, no snow expected.TUESDAY: Clear skies, freezing level rising to around 1200 m, light variable wind, no snow expected.

Avalanche Summary

Wind slabs were sensitive to skier triggering to size 2 on Friday on north and northeast facing slopes around 2000 m. These slabs were 10 to 25 m wide with crowns averaging 40 cm in depth. On Thursday wind loaded features produced natural avalanches to size 2.5. Several natural wind slab avalanches to size 2 were observed on steep north facing alpine terrain. Control work produced avalanches to size 2 in steep unsupported terrain.On Wednesday a natural size 1 wind slab was reported from an east facing feature at 1950 m. Isolated soft wind slabs were also being observed on steep convexities.

Snowpack Summary

The Coquihalla picked up a surprise 35 to 45 cm of snow Friday and Friday night with light easterly winds which is now hiding previously formed wind slabs. Mainly southerly winds formed these wind slabs as they interacted with up to 120 cm of storm snow that has fallen in the last week. All of the new snow rests on the February 23 weak layer. The February 23 weak layer is down 80 to 120 cm below the surface. This interface consists of wind hardened snow, facets, a sun crust on solar aspects and surface hoar that is present at and below treeline. Compression tests preformed Friday continue to show planar results at this interface. The mid and lower snowpack are well settled and strong.Variable winds in the past month have created cornices on many alpine ridgelines. They will become touchier as they grow in size, as temperatures rise, and as the strong late-winter sun shines down upon them on clear days.

Problems

Wind Slabs

The south of the region picked up 40 cm of new snow Friday with light easterly winds. Up to 120 cm of snow has fallen in the last week, and it all rests on a weak layer which may still be susceptible to human triggering.

Brief periods of sun could quickly initiate natural avalanche activity.The recent snow is now hiding wind slabs that were recently sensitive to human triggering.Avoid wind loaded terrain features, especially near ridge crests and roll-overs.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2.5

Cornices

Continued snowfall and strong wind from around the clock has formed large cornices on many ridgelines. Cornices are inherently unstable, unpredictable, and demand respect, especially when the sun is out.

Give cornices a wide berth when travelling on or below ridges.Watch out for overhead hazards, such as cornices, which could trigger slabs on slopes below.Avoid slopes when the solar radiation is strong, especially if they have large cornices overhead.

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 3

Valid until: Mar 4th, 2018 2:00PM