Avalanche Forecast

Issued: Apr 20th, 2013 10:43AM

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

jlammers, Avalanche Canada

South Coast.

Monday is the last day of the 2012/13 forecast season. As of Tuesday, general spring messaging will be found under the "Forecast Details" tab.

Summary

Confidence

Fair - Due to variable snowpack conditions

Weather Forecast

Saturday night - Sunday: Light to moderate snowfall in the south of the region (Coquihalla/ Allison Pass) on Saturday night. By morning skies are expected to be overcast with clearing in the afternoon / Light and variable winds / Freezing level at about 1500mMonday: Generally clear skies / Light north winds / Freezing level at about 1800m

Avalanche Summary

Throughout the past week, numerous rider triggered and isolated remote/sympathetic events have been reported in high (2300-2700m) north and northeast facing slopes up to size 2.5, all associated with preserved surface hoar. The aseems to be occurring in the north of the region in the Duffey Lake/ Birkenhead areas, through the Hurley and up towards Bralorne/Goldbridge.

Snowpack Summary

Generally light daily snow accumulations have been observed over the last week, with higher accumulations in the Coquihalla/Allison pass areas. Soft wind slabs likely exist on lee terrain. At lower elevations, spring temperatures have created isothermal snowpack conditions.About 30-60 cm below the surface lies the April 5th interface. On solar aspects, the layer is a strong melt-freeze crust, with some faceting observed above and below. On Northwest to Northeast aspects above about 2300m, this interface may be preserved surface hoar (up to 15mm). Where the surface hoar is present we have reports of sudden results in stability tests and have seen rider triggered, sympathetic and remote events up to size 2.5. Although this interface may be gaining some strength, continued reactivity is expected with the potential for large avalanches.Cornices are huge and will continue to grow with the forecasted precipitation.

Problems

Persistent Slabs

The April 5th interface lingers as a persistent problem, especially in the north of the region. Touchy surface hoar continues to be reactive on high, north-facing slopes.

Be aware of the potential for large avalanches due to the presence of buried surface hoar.>Dig down to find and test weak layers before committing to a line.>Be alert to conditions that change with elevation.>

Aspects: North, North East, East.

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 5

Loose Wet

Loose wet avalanche activity will be likely in steep terrain, especially as the sun comes out on Sunday.

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

Possible - Likely

Expected Size

1 - 4

Wind Slabs

New softslabs may continue to form in lee of features with snow forecast for Saturday night. The only significant accumulations are forecast for the south of the region.

Be cautious as you transition into wind affected terrain.>Stay off recent wind loaded areas until the slope has had a chance to stabilize.>

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 4

Valid until: Apr 21st, 2013 2:00PM