Vancouver Island Avalanche Bulletin

Vancouver Island Avalanche Bulletin

Date Issued: Thursday 17 December, 2009

Valid Until: Sunday 20 December, 2009

Bulletin Area: This bulletin covers the mountainous region of Vancouver Island from the Mt. Cain Ski Area in the North to the Beaufort range to the South including the mountains of Strathcona Provincial Park.

DANGER RATINGS

Confidence:

Fair - Field observations are still limited especially in the high alpine. Also models disagree on the timing and amounts of precipitation for Sunday.

Weather:

The island mountains have seen plenty of precipitation since later Monday with 66mm of precipitation on the east coast of the island, around 80mm in the mountains mid island and up to 123mm on the west coast. The bulk of this came late Tuesday and into Wednesday. Freezing levels did not shoot up quite as high as predicted in our last forecast meaning that most of this precipitation came as snow at the elevations of interest to mountain recraeationists. The passage of a warm front at the time of writing will be followed by a trailing cold front which will see precipitation trailing off Friday. A ridge of high pressure will bring mostly sunny skies on Saturday with another frontal system bringing snow again by Sunday.

Avalanche Activity:

Natural avalanche activity to size 1.5 has been reported at and below tree line on Wednesday. Explosives and ski cutting produced avalanches of size 1 to 1.5 on Tuesday and of up to size 2 on Mount Washington on Wednesday. There are no observations from the high alpine but it is very likely that a natural avalanche cycle took place there on Wednesday. Most reported activity was sliding on facets on the old snow surface.

Snow Pack:

All reported avalanche activity from this past cycle slid either within new snow and more often at the new snow/old snow interface on faceted crystals. While it is imagined that this cycle will have “cleaned out” much of this hazard it is also possible that places remain where this has not been triggered and may still be susceptible to human triggers. There is also an unknown in the high alpine trigger zones in the form of faceting below crust layers near the surface. These may well have triggered as natural avalanches on Wednesday but may also remain ready for human to help them reach critical load. Generally speaking there is a lot of windslab around at tree line and in the alpine.

Outlook:

Continued precipitation Thursday night bringing another 8-12mm of water with freezing levels above tree line. Precipitation will trail off Friday morning and freezing levels will drop to 1000m and below. Saturday will be mostly sunny with Freezing levels dropping further to 500-700m. Sunday will see increasing cloud and a rise in freezing levels with models disagreeing on the timing and quantity of precipitation that may come later in the day. Winds will be light to moderate from the S on Friday shifting to N on Saturday and then E later Saturday and Sunday.

Are you traveling in the island back country?

Send our forecasters your observations. We are particularly interested in hearing if you have observed avalanche activity or If you or a member of your party has been involved in an avalanche. Email your observations to the Island Avalanche Bulletin forecasters at info@islandalpineguides.com

Important Notice: This is a regional forecast and significant variation may exist within the forecast area. The information and danger ratings are intended as a trip planning aid for recreational, backcountry users of avalanche terrain; they are not meant to be used as the sole factor in determining the avalanche danger presented by a specific slope. Always include local weather, snowpack and avalanche observations in your decision to travel in avalanche terrain. Observations and experience may lead to different conclusions from what is reported or recommended. See disclaimer for further details. The technical data used to produce these bulletins is obtained from a variety of sources, including local ski areas and remote weather resources.