CANADIAN AVALANCHE ASSOCIATION BACKCOUNTRY BULLETIN _JANUARY 13, 1997_ _SOUTH COAST & VANCOUVER ISLAND_ _WEATHER:_ A high pressure ridge has been slowly building for the last few days, and will remain stationary over most of BC for the week. There is little chance of significant precipitation, and daytime temperatures are going to be very pleasant. _SNOWPACK:_ The new snow of last week is gaining strength rapidly. The entire snowpack is settling, so stability is improving. The snowpack may become isothermal wherever it is shallow on south and west facing slopes by mid afternoon, particularly in areas around rocks and clumps of trees. The North Coast snowpack still contains a weakness on the crust/facet interface laid down in mid November and now deeply buried. _AVALANCHES:_ There are a few reports of small activity in the upper snowpack, mostly from the North Coast. Very little natural activity now, although smaller isothermal avalanches are likely to begin in the afternoon from solar radiation. _DANGER:_ _Moderate_. _TRAVEL ADVISORY:_ Certainly not the time to completely throw caution to the wind, but the week has all the makings of an excellent time for a tour. What little natural activity which was being reported was occurring on very steep slopes, so use caution if you are on the steeps. _NORTH COLUMBIA_ _WEATHER:_ The powerful high which has established itself over the west is bringing good weather to the North Columbias also. Some cold air has flowed into the region from the arctic outbreak on the Prairies, giving colder overnight lows and some inversion conditions. Clear skies, cold nights, and comfortably warm days. _SNOWPACK:_ The deep instability continues to produce large avalanches. The problem layer, laid down in mid November, is now part of the lower snowpack. It consists of a thick ice crust, with very weak facets overlying. The layer often is poorly supported below as well. Above the whole thing is one to two metres of denser snow. This snow has enough weight, the problem layer is active throughout the region. _AVALANCHES:_ Reports of natural, skier triggered and explosive released avalanches to size 4 abound, most on skiable inclines. Avalanches are triggering remotely; one party felt a settlement and saw a large avalanche begin 800 metres away. One avalanche often triggers several others in sympathy, so when something moves, it usually propagates widely. One helicopter bombing crew around Revelstoke saw an explosive charge thrown into one path release an avalanche over a ridge top in the next basin. _DANGER:_ _High_. _TRAVEL ADVISORY:_ The upper snowpack feels dense and safe, but the instability is deep and can only be investigated with a pit. The weather will be pleasant during the days, but don't let this take your mind off careful choice of terrain if you are out. _SOUTH COLUMBIA_ Clear skies will predominate here for the week. The inversion conditions will be present in the South Columbias as well, but the warm air up high will not get much above zero. _SNOWPACK:_ Some variability within the region. On the east side of the South Columbias, where the snowpack is shallower, the ice crust/facet interface developed in November and can still be found. Where the snowpack is deeper on the west side of the range, the layer is not as well developed. In the southern extremes of the entire range, the layer is not found. _AVALANCHES:_ The only consistent reports of natural activity are coming from the Invermere, Bugaboos area. These areas have reported a few natural avalanches to size 2.5, and the common factor seems to be they are occurring in areas of shallow snow. No reports of activity in the south, the upper snowpack has settled out and ski penetration is light now. _DANGER:_ _Moderate_ in the south and along the west side of the range. _Considerable_ along the east, with increasing potential as you move north. _TRAVEL ADVISORY:_ With the North Columbias still locked in the full scale cycle of large, deep avalanches, the South Columbias are certainly an attractive destination. Keep in mind the variation in conditions discussed above. A great week for a trip. _ROCKIES_ _WEATHER:_ The Rockies are still being influenced by the Arctic air which flowed into the region over the weekend. Overnight lows are only getting down to the -25 range, so the mountains are definitely warmer than Calgary and Edmonton. Daytime solar radiation is bringing the temperature up to a very pleasant level, approaching zero on sheltered south facing slopes. _SNOWPACK:_ Overall, the warm days are promoting a slow trend of stabilisation. The mid snowpack in the north part of the Rockies is weak, and this is more prevalent as you move higher in elevation. In the south, around Fernie/Waterton, this weakness is not being reported. _AVALANCHES:_ A close call at Bow Summit on the weekend, where some people triggered a slide but skied out of danger in time. Naturals to size 2.5 being reported in Jasper and Banff, and highway control operations in the Columbia Icefields area produced explosive triggered slides to class 3. The stations throughout the 4 mountain parks are seeing natural activity in the backcountry. No activity reported from the stations in the South Rockies. _DANGER:_ _Considerable_, particularly at treeline and above. _Moderate_ in the South Rockies. _TRAVEL ADVISORY:_ Expect to see changes throughout the day in the upper pack, with the cold overnight freezing things up, but upper layers weakening throughout the day from solar radiation. The clear skies will make for pleasant days, and with careful attention to route selection, its good touring weather. Have a good look at the mid and lower snowpack before you jump into something, particularly in the 4 Mountain Parks area. Downhill skiing should be excellent after the morning crust warms up. The Bulletins will be issued on Monday and Thursday. THIS BULLETIN SPONSORED BY Edmonton Section, Alpine Club of Canada _________________________________________________________________ Contact numbers for the Avalanche Bulletin are: