Vancouver Island Avalanche Bulletin

DANGER RATINGS (Make sure you understand the danger level meanings)

Outlook	Monday	Tuesday	Wednesday
Alpine	HIGH	CONSIDERABLE	HIGH
Treeline	CONSIDERABLE	CONSIDERABLE	HIGH
Below Treeline	CONSIDERABLE	CONSIDERABLE	CONSIDERABLE

Confidence:  Moderate. While the pattern is clear, exact timing and intensity can easily vary from what is forecast below.

Ratings above are for areas of highest precipitation. Watch precipitation amounts for the area you are traveling in.

 Main Concerns: (Avalanche problems)

1. Wind Slab - Wind slab has been created on weak layers by winds predominantly from the SW to SE but in fact from all directions at some point. These slabs will continue to form with more new snow and wind in the forecast.
2. Storm Slab - With sufficient quantities of new snow and snow driven by wind, load will increase on weak layers making natural avalanches likely on all aspects in the alpine and possible at tree line and below.

A series of systems crossed the island since Friday leaving a total of between 25 and 90mm of water. Greatest amounts where on the west coast with lesser amounts on the east and north island. Much of this precipitation came as snow to about 1000m and above but it did turn to rain for some time up to tree line. Winds were moderate to strong predominantly from the SE through to SW though during breaks in the systems the winds shifted around to the opposite side of the compass. The forecast is for another series of fronts this week:

Monday: 15-25mm of precipitation (greater amounts west and north island). Moderate to strong SW winds (greater strengths at the highest altitudes), Freezing level around 900m.

Tuesday: 5-10mm of precipitation. Light to moderate SW winds. Freezing levels 300-1000m.

Wednesday: 20-35mm of precipitation (greater amounts west and north island). Moderate to strong SW and W winds. Freezing levels rising to tree line and above.

Snow Pack:

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. Areas below tree line which are sheltered from both wind and sun have surface hoar lurking below which will likely receive sufficient load to trigger with the coming precipitation. The mid pack is very strong. The base of the snowpack has faceted crystals which are likely to strong to fail in most places though with increasing loads some very specific areas (shallow and rocky in the highest alpine only) may warrant attention.

Avalanche Activity:

Wind slabs have been touchy to human triggers and have been ski cut easily. We do not have reports of natural avalanche activity over the week end though we have a forecaster in the field today and will report on his findings.

Travel Advice:

Stay out of avalanche terrain during times of Considerable and High hazard. If you don't know what avalanche terrain is, take an avalanche course to learn to distinguish avalanche terrain. Stick to low angled and well forested slopes and stay away from wind loaded areas near ridge crests and in places which are "cross loaded". Watch for signs of instability in the snow such as natural avalanches, "whumpfing" sounds, cracking, shooting cracks and hollow sounds.

 

 

Prepared by Jan Neuspiel