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 Banff, Yoho and Kootenay National ParksIssued:Sunday, February 24, 2008 16:00Valid Until:Monday, February 25, 2008 16:00Bulletin Area:This forecast covers the east and west sides of the Continental Divide from the Wapta Icefields area in the north to the Sunshine area in the south. It also includes the Main Range area from Lake Louise to Bow Summit.
Synopsis:A light dusting of flurries fell today under upslope conditions, but with a generally overcast sky and virtually no wind to speak of there were really no new inputs to the snowpack. The sensational, spring like weather over the last week has helped stabilize weaknesses in the upper snowpack, through steady settlement. Shears in the upper snowpack are now generally producing moderate test results.However, given the season , the warm temperatures are really only having an affect for a few hours a day, and only on solar aspects. For the other 20 hours of the day, cooler air temperatures are the reality. With a generally shallow snowpack and a more consolidated upper snowpack, preventing warmer temperatures from penetrating to the basal facets, a faceting temperature gradient still exists. Therefore, little improvement to the overall snow stability is actually occurring. What we are seeing is a greater potential for avalanches that do start, to propagate greater distances, given the consolidated upper snowpack that overlies the weak basal facets. We're still getting moderate compression test results in the basal facets. Monday, should see a return to brilliant sunny skies, as a ridge of high pressure returns to the forecast area. Once again, sunny solar aspects, that have yet to avalanche, should be avoided or steered clear of during the heat of the day. The Danger Rating on Southerly aspects will rise to High, as the sun warms the upper snowpack, causing it to creep down hill and eventually overcome the shear strength it has with the layer below. As we have seen, the resulting avalanches will likely step down to ground, resulting in a destructive, full-depth slide. Steeper, unsupported slopes on more northerly aspects, at treeline and above, remain probable locations for human triggered avalanches. Snow depths at these elevations vary considerably, due to previous wind events this season. Hard turns on the thinner snowpack areas, or large groups in a single location, will certainly overload the bridging strength of the upper snowpack and lead to a failure in the basal facets. Backcounrty users must have the mind-set that this years instabilities are persistent and are not likely to improve until we are well into true spring conditions, where the warmth penetrates to ground and rounds-out the basal facets. Avalanche Activity:No new avalanches reported today.Outlook:Light winds, unseasonably warm temperatures and a potential for a dusting of snow is the weather forecast for the majority of the coming week. With broken skies expected, solar affect should be limited. However, local sun effect could be significantly different from one drainage to the next, so keep an eye on overhead hazards, like cornices or south facing start zones that may be feeling the full affects of the sun for extended periods.Travel Conditions:Shaded, Northeasterly aspects, at and below treeline are the places to be right now for turns. Solar aspects harbor a suncrust of varying thicknesses, none of which consistently support a rider. Hateful conditions were had today in Kootenay NP, on a Southwest face along the Honeymoon Pass trail. Uptracking was good through the burnt trees, hopefully our efforts to track the sun's affects and current state of the developing surface hoar, through barely threshold snow depths and breakable crusts, will be chalked up to good karma. MG
FOR MORE DETAILS:Warden Office: (403) 762-1470 Emergency: 403 762 4506 24 Hours Recorded Message: 1-800-667-1105 Related Link: http://www.avalanche.ca/ Seasonal Archives |
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