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Backcountry Advice

Cornices have grown immensely


As of Wednesday, Feb. 8, 2006

Alpine: MODERATE trending Considerable with exposure to the sun

Treeline:  LOW trending Considerable with exposure to the sun

Below Treeline: LOW

Travel Advisory: 35cm of snow has fallen since last Friday night. Saturday’s snowfall was accompanied by extended periods of strong winds from the E and SE, leaving the high alpine terrain somewhat battered. Most of the reactive windslabs that formed were small, involving only the most recent snowfall layers. We did, however, see some deeper slabs running below a stiff windslab that formed on Jan. 31. These slabs were sizeable and appeared to be triggered around heavily loaded rocky areas on N and NW aspects. Cornices have grown immensely and have been pulling back onto the flats when they break. Stay well away from the edges.

Avalanche Activity: Explosive and ski testing carried out after the storm cycle produced some small windslabs with crowns to about 20 cm in depth. During this period we also saw some isolated deeper releases that seem to be running under a buried windslab that formed on Jan. 31. One slab appeared to initiate in the overnight storm snow and then pulled deeper, producing a crown line that was up to 100 cm in depth. The debris from this avalanche then triggered another 100-130 cm deep slab on a pillow below the Hanging Roll. On Saturday afternoon a skier triggered another deeper release on another similar slope. As mentioned above, these deeper releases all seem to have a rocky start zone and/or trigger point in common. Last week another deep slab was observed to have stepped down to the Jan. 19 surface hoar layer buried 110 cm down on an Eastern aspect at 1950 metres.

Snowpack: The snowpack is extremely variable due to the strong winds that blasted our area on Friday and Saturday. The older storm snow layers have for the most part continued to settle in and gain strength. In some pockets of terrain, the previously mentioned buried windslab is overlying a less dense layer of storm snow. Subsequent snowfall seems to have added enough of a load to stress this interface. The shears that we were seeing over the weekend have continued to tighten-in, but the fresh windslabs that developed through the day on Tuesday and on Tuesday night can be expected to be reactive to the weight of a person in some isolated areas. In some alpine and treeline areas you will find a layer of buried surface hoar crystals lying about 100 cm below the surface. Below the 2000 metre elevation a thin melt-freeze crust can be found under the 4 cm of snow that fell last night, with another thin crust down approx. 15-20 cm. Below about 1600 metres you will feel a thin melt-freeze crust approximately 15-20 cm below the surface at lower elevations below the treeline.

Weather:  The ridge of high pressure will rebuild today bringing sunny skies and mild temperatures on Thursday and Friday. A weak disturbance may penetrate the ridge over the weekend.

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 604-938-7676, or at 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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