Avalanche Forecast

Issued: Apr 21st, 2014 9:26AM

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.

esharp, Avalanche Canada

South Columbia.

Avalanche danger will be greatest in the band at and above treeline where rain falls on previously dry snow which may lie above an older crust.

Summary

Confidence

Poor - Due to the number of field observations

Weather Forecast

Synopsis: A southerly flow will generate widespread precipitation over the southern interior Tuesday and Wednesday before a weak ridge ushers in drier conditions on Thursday. Temperatures will remain warm through the first part of the forecast period.Tonight and Tuesday: Moderate precipitation - up to 15 cm of snow at upper elevations / Moderate southerly winds / Freezing levels between 2000 and 2400m.Wednesday: Light precipitation - 5-10 cm of snow / Moderate westerly winds / Freezing levels falling to between 1500 and 1600mThursday: Sunny with cloudy periods and a chance of flurries / Light southwesterly winds / Freeing levels around 1800m

Avalanche Summary

Small slabs have been recently triggered naturally and by skiers in areas where the upper snow is moist and sits above a crust. At lower elevations and on solar aspects small to large loose wet avalanche continue to be triggered on steep slopes. Cornices collapses have been reported during periods of daytime warming. Occasionally these heavy triggers have caused large deep slab avalanches on the slopes below.

Snowpack Summary

Moist snow or a fresh crust may be found on the surface on slopes that have seen recent sun. Between 20 to 40cm of snow overlies several widespread melt-freeze crusts on all but high elevation North aspects. Wind slabs can be found in lee features on N and E aspects in the Alpine.Several persistent weak layers exist in the highly variable snowpack of the South Columbia region:- The mid-March sun crust/surface hoar layer down 50-80cm and the early-March crust/facet/surface hoar layer down around 80-120cm seem to be inactive.- The mid-February crust/facet/surface hoar combo is typically down 150 - 200cm. Human triggered avalanches on this layer are unlikely. Larger triggers such as cornice fall, a smaller avalanche in motion or prolonged warming could wake this layer up, resulting in very large and destructive avalanche.

Problems

Storm Slabs

Expect to see an increase in avalanche activity where rain affects previously dry snow. At higher elevations expect winds slabs will form on north aspects.

Be careful with wind loaded pockets, especially near ridge crests and roll-overs.>Avoid avalanche terrain during periods of rain.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 3

Loose Wet

Expect to see an increase in loose avalanche activity were the forecast rain saturates the upper snowpack.

Avoid slopes with glide cracks.>Avoid steep, open glades in the forest.>