Avalanche Forecast

Issued: Feb 26th, 2013 9:55AM

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.

ccampbell, Avalanche Canada

Sea To Sky.

Summary

Confidence

Fair - Timing of incoming weather is uncertain on Thursday

Weather Forecast

Wednesday: Another 10-15 cm is expected overnight Tuesday, before things start dry out for Wednesday, but expect continued cloud cover with another 3-5cm throughout the day. Winds are expected to ease off to light southwesterlies and freezing levels could reach 1000m late in the afternoon. Thursday: A relatively dry, cool and calm morning before a warm and wet frontal system makes landfall sometime in the afternoon. Friday: Heavy snowfall, strong southerly winds and freezing levels as high as 1800m.

Avalanche Summary

Reports from yesterday include several human triggered slab avalanches up to Size 2.0, involving wind slabs, recent storm snow weaknesses, as well as the persistent weakness buried early last weak. Some of the avalanches involving the persistent weakness were remotely triggered from as far as 50m away. A size 2.5 avalanche was triggered by a party of sledders on Sunday in the Brohm Ridge area, and left a man buried 1.8 metres below the surface. The man was successfully rescued. Check out the Forecaster blog for the full story.

Snowpack Summary

Surface hoar, facets, and/or crust buried early last week are now 60-100cm deep, depending on the area, and remain touchy. Fresh wind slabs, buried wind slabs, and recent storm snow weaknesses in the upper snowpack are highly reactive to human triggers and have the potential to step down to this persistent weakness, or deeper to another persistent weaknesses buried earlier in the month. Cornices are also large and unstable.

Problems

Storm Slabs

New and recent storm snow is expected to become very touchy with continuous loading throughout the forecast period, especially where wind-loaded. Thinner slabs failing within the recent storm snow may step down to old snow surfaces from last week.

Choose well supported terrain without convexities.>Be cautious as you transition into wind affected terrain.>Avoid freshly wind loaded features.>Give cornices a wide berth when travelling on or below ridges.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 4

Persistent Slabs

An assortment of persistent weaknesses lurk in the top 100cm. Most notably is surface hoar buried early last week, which is most concerning in sheltered treeline areas.

Remote triggering is a concern, watch out for adjacent slopes.>Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 5

Valid until: Feb 27th, 2013 2:00PM