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Backcountry advisory

January 30, 2008

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Alpine: Considerable

Treeline: Moderate

Below Treeline: Moderate

Travel Advisory: 28 cm of cold, low density snow has fallen since Saturday, 10 cm of which arrived during the past 24 hours. Moderate winds accompanied the most recent snowfall, initially from the southeast, switching to the southwest yesterday afternoon. The low density surface layers of snow have been readily transported by the wind, resulting in soft slab formation to the lee of ridge-tops and any terrain features in the high alpine. In some areas the wind pressed surfaces from last week’s outflow winds are still very much in evidence. Keep in mind that large unpredictable avalanches are still very much a possibility, particularly if a cornice fall is involved.

Avalanche Activity: Ski testing carried out yesterday morning and some explosive testing this morning produced some size one soft slabs from 10 to 25cm in depth, with some isolated pockets up to 40 cm deep with moderate propagation. The most recent activity on the Dec 4 Crust and facet layer was on January 21st and was initiated by a large cornice fall.

Snowpack: The snow that fell overnight and on Saturday was overlying a variety of old hard surfaces that were created by last week’s strong northeast winds and sun. Surface hoar up to 10 mm in size formed last week at treeline and below on top of a layer of faceted snow. These layers are now buried by up to 30 cm of loose and unconsolidated storm snow, and up to 50 cm deep in the Powder Mountain region. In some locations in the vicinity of any creek beds these crystals are much larger and could provide a failure plane for future avalanche activity with additional loading. The Dec. 4 raincrust and facet crystal weakness is well buried in most areas, and although it has gradually been gaining strength, it has continued to pop up sporadically. Its unpredictable and persistent nature has been problematic and backcountry travelers should continue to be cautious. The deep slab releases have generally appeared to initially fail in a shallow part of the slab in rocky start zones, propagating into the deeper areas.

Weather: Snow flurries Wednesday will become steady snowfall this afternoon as this next system arrives onshore, with strong mountaintop winds expected to develop overnight tonight. Steady snowfall tonight will taper off to flurries tomorrow afternoon with the passage of the front. A continued cool and unstable northwesterly flow will bring scattered flurries on Friday and Saturday, with the next organized system expected to arrive onshore on Sunday.

Conditions may vary and can change rapidly. Check for the most current conditions before heading out into the backcountry. Daily updates for the areas adjacent to Whistler/Blackcomb are available at 938-7676, or surf to www.whistler-blackcomb.com/weather where there is also a link to the CAA public avalanche bulletin, or call 1-800-667-1105

Whistler Mtn. Snow Safety

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