Vancouver Island Avalanche Bulletin

Valid Until: Monday 2 January, 2012.

Confidence:  Moderate. timing and intensity of precipitation as well as freezing levels are uncertain.

Main Concerns: (Avalanche problems)

Wind Slab - Thick wind slab has been created by winds predominantly from the SW in the lees of ridges and in cross loaded features. These slabs will fail under human loads.

Persistent Slab - Increased load from snow, rain or wind driven snow could bring instabilies deeper in the snowpack on all aspects to the point where they will fail under human loads or even release naturally.

Weather:

The last 48 hours have brought between 25 and 40cm of snow to the island mountains. The snow came with moderate to strong winds mostly from the SW. The outlook is as follows:

Saturday: Light snow with little accumulation. Winds shifting from light NW to light to moderate SW with the approach of the next front. Freezing levels around 700m

Sunday: 10-25mm of precipitation will start as snow but may turn to rain as freezing levels head up toward the tops of the island alps by late in the day. Winds moderate and increasing to strong SE to SW.

Monday: Some clearing earlier in the day to be replaced by clouds, renewed precipitation and moderate SW winds as the day goes on. Accumulations 5-10cm by days end with freezing levels dropping back down to about 1200m.

Snow Pack:

The island snowpack varies quite a bit from the east coast to the west and north island. Snowpack conditions described below may or may not apply exactly to the area that you are in so local investigation is important. In the alpine and at tree line thick wind slabs overlie weak faceted snow at crusts. These slabs are easily triggerable by human loads and render easy, planar test results. With increased load on Sunday these may release naturally or at least become more susceptible to human triggers. Areas below tree line which are sheltered from both wind and sun may have surface hoar lurking below. The mid pack is very strong. The base of the snowpack has faceted crystals which are likely too strong to fail in most places.

Avalanche Activity:

Conditions over the past few days have not been conducive to travel in the alpine so we have limited observations but we have seen evidence of natural avalanche activity at tree line and below indicating that a more widespread natural cycle likely occurred in the alpine.

Travel Advice:

Choose lines that avoid wind affected terrain. Watch for signs of instability such as hollow drum like sounds, cracking and shooting cracks in the snow and whumpfing. Watch precipitation amounts in the system coming Sunday. With increased load weaknesses deeper in the snowpack may be activated. Notice that cornices have been built up in the last while. These are hazards in their own right, are large potential triggers for avalanches and their failure is difficult to predict. Give them a wide berth.

Prepared by Jan Neuspiel