Avalanche bulletin Info

lulululu · 发表于 2011-5-12 20:45:43

Special Message

This bulletin describes conditions likely to exist in this region for the weekend of May 14 – 15, 2011 and provides general advice for managing risk in these conditions. This information will be updated on Thursday, May 19, 2011. We advise consulting with knowledgeable, local sources to obtain information about current conditions before venturing into the backcountry. Current or recent information may also be found in online forums and if we get photos of recent slides, we’ll post them in our avalanche image galleryavalanche image gallery.

Confidence: Good

We no longer have enough data to produce a regular forecast for this region. This bulletin is based primarily on previous knowledge of snowpack and avalanche conditions, weather observations from automated stations, and the weather forecast. If you have information or observations from this region, please send them to: forecaster@avalanche.ca.

Weather Forecast

Generally clear and dry on Friday before another Pacific frontal system brings moderate to locally heavy rain for the weekend. Expect 15-20mm on Saturday and up to 35mm on Sunday with freezing levels well above mountaintops. Continued unsettled and wet conditions are expected for Monday.

Avalanche Activity

Wet loose or slab avalanches are possible, depending on weather. Spring slides can run farther and gather more mass than expected, often producing large destructive avalanches. Very deep, even full-depth avalanches are possible if extended periods of thawing without overnight refreezes occur and/or if significant rainfall soaks the snowpack. Recent or new avalanche activity is a clear signal that a high degree of caution is required. Learn more about avalanche types and associated risk management by reading the Avalanche Problem Essentials documents found in the Decision Making section of the CAC website.

Travel Advisory

Avalanche danger over the weekend will be closely related to freezing levels and precipitation. Danger is generally lower when and where temperatures are cool and rain is not affecting slopes. Danger increases as temperatures rise, rain intensifies, and surface snow becomes wet or slushy. Be prepared to alter plans, adjust routes to avoid avalanche terrain, or even turn around and go back if you see signs of increasing danger, such as:

Pinwheeling
Snowballing
Or wet loose avalanches

Be vigilant and keep an eye on what's going on above and around you at all times. A sluff, a loose wet slide, or a cornice failure could hit you from above, even if you’re in Simple terrain.

If it snows and especially if new snow is being transported by wind, avalanche danger is generally highest:

During and shortly after storms or squalls.
In lee and cross-loaded terrain.
If more than 30cm of new snow falls.

If there's any doubt about avalanche danger, use travel techniques that minimize risk:

Travel across or down steep slopes one at a time.
Spread out when crossing runout zones.
Regroup in dense timber or on high ground; and travel on ridges whenever possible, but give cornices a wide berth.

A probe, shovel, and avalanche transceiver, are essential when traveling in, through, or under avalanche terrain. The way this season is going this equipment is going to be necessary much longer than normal—perhaps even into early summer. Obtain rescue training before heading out and practice rescue techniques regularly. If you are buried in an avalanche, you will likely not survive if your companions are not able to quickly find you and dig you out. Finally be on the lookout for deep open creeks and sinkholes.

Snowpack

The snowpack at upper elevations is unusually deep creating more and larger open slopes than normal. The surface snow is becoming pretty wet and sloppy with no overnight freezing and surface crust formation. In many areas the entire snowpack is becoming warm and weak, and loosing its ability to cling to steep mountainsides.

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