Avalanche Forecast

Issued: Dec 14th, 2013 8:25AM

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

jlammers, Avalanche Canada

South Columbia.

Summary

Confidence

Fair - Intensity of incoming weather systems is uncertain

Weather Forecast

Overnight Saturday and Sunday: Moderate snowfall becoming light on Sunday / Strong to extreme westerly winds / Freezing level at 1100mMonday: Flurries / Moderate to strong Westerly winds / Freezing level at 600mTuesday: Heavy snowfall / Moderate southerly winds with extreme gusts / Freezing level at 1200m

Avalanche Summary

Several natural slab avalanches to size 2.5 occurred in the Selkirks on Friday. These avalanches occurred on various aspects in wind-affected terrain.I would expect more slab avalanche activity in the wake of snow, wind and moderate temperatures on Saturday.

Snowpack Summary

Since last week's cold snap daily snowfall amounts have generally been in the moderate range. Although accumulations have been variable, roughly 60cm of snow now overlies the weak faceted crystals or small surface hoar which formed during the cold weather. On lower elevation slopes rising temperatures are expected to have enhanced the slab properties creating a more reactive "upside-down" snowpack. Moderate to strong southwest winds have created wind slabs in exposed high elevation terrain.As of late there has been no reported activity on the late-November interface which consists of sun crusts on steep south facing slopes and surface hoar in sheltered areas. This layer, buried between 60-80cm below the surface, is generally considered to be "stubborn" to trigger; however, avalanches at this interface could have nasty consequences.Weaknesses towards the base of the snowpack are mostly thought to be dormant at this time.

Problems

Storm Slabs

Ongoing snowfall, wind and moderate temperatures will add to a developing storm slab problem. Watch for increased reactivity in wind-affected terrain or at elevations where the upper snowpack has been affected by warming.

Be alert to conditions that change with elevation.>Be cautious as you transition into wind affected terrain.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 4

Persistent Slabs

Moderate temperatures may increase the reactivity of an assortment of persistent weaknesses buried in the mid and upper snowpack. Triggering a persistent slab may have nasty consequences.

Dig down to find and test weak layers before committing to a line.>Caution around convexities or large, unsupported slopes.>Make observations and assess conditions continually as you travel.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

3 - 5

Valid until: Dec 15th, 2013 2:00PM