February 5, 2001 NOTICE OF UNUSUAL AVALANCHE CONDITIONS: Valid until further notice. This season avalanche professionals between the Inner Coast Mountains and the Rocky Mountains have observed snowpacks that are unusually weak. The combination of below normal snow depth and low temperatures has produced layers of facetted grains and surface hoar with a low strength. These types of weak layers can persist for a long time, and the avalanche danger will increase with every load of new snow onto this weak base. The present snowpack is less stable than in most other years and remarkably different from the snowpack at the same time last winter. Back country users will have to pay much attention to snowpack structure and strength during this winter. Note: Check out the new updated Western Canadian Avalanche Information on the CAA website, at www.avalanche.ca\Bulletin.html. The new page provides quick and easy access to every bulletin available on the web in Western Canada. One stop shopping, including bulletins, weather, satellite imagery, road conditions, and coming soon, interactive discussion boards on regional conditions! SOUTH COAST REGION WEATHER: After an extremely windy start to the weekend, the wind calmed down on Sunday along with an additional 20 cm of light and fluffy snow. Total accumulations over the last week reached up to 100 cm in some places. A slight cooling trend began on Sunday, with temps dipping down to almost ^Ö15 on the lee side of the range. Expect the cooling trend to continue through the week as a NW flow develops. Intermittent snow flurries are possible through the week with light accumulations. SNOWPACK: The wind hammered just about everything it could find, stripping windward slopes and creating big loads on the lee slopes. These instabilities seem to have bonded for the most part, leaving 20 cm of light snow on the surface. On the east side of the range, areas of buried surface hoar exist under the recent storm snow and are most obvious at treeline. Concern with a facetted base remains on the east side of the range, with shallow areas particularly suspect. The most consolidated snowpack appears to be in the Whistler area. AVALANCHES: Little avalanche activity was observed in the Whistler area. East side areas (Coquihalla/Gold Bridge) continue to see avalanches triggered, mainly within or just below the storm snow layers. FORECAST OF AVALANCHE DANGER UP TO THURSDAY EVENING (FEB 8) ALPINE ^Ö Moderate (Considerable on the east side of the range) TREELINE ^Ö Moderate (Considerable on the east side of the range) BELOW TREELINE ^Ö Moderate TRAVEL ADVISORY: As the deeper snowpack becomes better consolidated, it^Òs important not to forget about the facets that were such a concern just a short time ago. These crystals still exist; it^Òs just that they have become stronger. It is likely still possible to trigger them if you hit the sweet spot on a shallow slope. Treeline and moraine areas are spots to watch out for and exercise good route selection. NORTH COLUMBIA REGION WEATHER: Snowfall continued throughout the region over the weekend with accumulations ranging from 75^Ö100 cm at higher elevations. Variations in wind intensity and temperatures were observed each day, but generally speaking, moderate westerly winds and temps ranging from 0 to ^Ö10 were observed. Weather forecasts are predicting a drying and cooling trend as a NW flow develops over the province, but don^Òt be surprised if snow flurries are affecting your area. SNOWPACK: With the recent accumulation of storm snow, instabilities have been observed at various levels in the snowpack. In the top meter of snow instabilities exist with the storm snow itself; and lurking anywhere from 75-125 cm down is a layer of surface hoar buried early last week. Both of these interfaces are of serious concern as skiers or snowmobilers could easily trigger layers buried at this depth. A persistent layer of weak facets remains near the ground as well. Although this layer appears to be gaining some strength, it continues to regularly produce large avalanches. AVALANCHES: Widespread natural, human and explosive triggered avalanches were observed over the weekend. Most of these avalanches have been occurring in the upper half of the snowpack, with last weeks buried surface hoar the main culprit. In Glacier Park, explosive control produced a healthy size 3.5 avalanche which failed on the facetted layer near the ground. FORECAST OF AVALANCHE DANGER UP TO THURSDAY EVENING (FEB 8) ALPINE ^Ö High ^Ö improving trend TREELINE ^Ö High ^Ö improving trend BELOW TREELINE ^Ö Considerable TRAVEL ADVISORY: With at least three separate instabilities to keep track of in the snowpack, accurately predicting avalanche hazard on specific terrain has become quite complicated. Digging down and looking for surface hoar yourself is essential, and the rutchblock test is well suited for these sorts of conditions. No snowpack tests will accurately evaluate the facetted base, so your best option is to avoid any large, avalanche prone features. SOUTH COLUMBIA REGION WEATHER: Storm snow accumulations over the past days have reached 50-80 cm, and were accompanied late in the weekend by a slight cooling trend. Expect this cooling trend to continue into the week as a NW flow dominates this week^Òs weather pattern. The strong winds of late last week abated over the weekend, allowing light to moderate westerly winds to effect exposed areas at and above treeline. SNOWPACK: Although instabilities are present within the recent storm snow itself, a layer of surface hoar buried by this storm is a prime concern and can be found 50-75 cm down from the surface. In some locations, the surface hoar is combined with a buried sun crust to exaggerate the problem. A serious concern continues to exist with the November facets and depth hoar which prevail near the base of the snowpack. This extremely weak layer continues to be triggered and predicting its behavior is difficult at best. AVALANCHES: Avalanches continued to be triggered by humans and explosives, failing mainly on the buried surface hoar, but several large avalanches were also released on the facets near the base. Some natural avalanches were also observed, mainly at treeline areas. FORECAST OF AVALANCHE DANGER UP TO THURSDAY EVENING (FEB 8) ALPINE ^Ö High ^Ö improving trend TREELINE ^Ö High ^Ö improving trend BELOW TREELINE ^Ö Considerable TRAVEL ADVISORY: Conditions are ripe for a major avalanche cycle in this region. The only thing preventing widespread avalanching is the properties of the snow near the surface. Slight changes such as increased wind, sun exposure or rising air temperatures have the potential to create slabs near the surface which will react on the buried surface hoar. With respect to the facetted base ^Ö not too many options exist for dealing with this layer except avoidance of large, avalanche prone features. ROCKIES REGION WEATHER: Light snowfalls continued to dribble into the Rockies over the weekend, with total storm accumulations of 20-40 cm depending on location. Moderate westerly winds and slightly cooler temperatures in the ^Ö5 to ^Ö15 range prevailed. Forecasts for the coming week show the pattern shifting to a NW flow, which should bring temperatures down to the ^Ö20^Òs, and the possibility of light snow. SNOWPACK: Moderate to strong westerly winds combined with the recent storm snow to create windslabs at treeline and above, which are likely reacting to light triggers. In most locations, this recent storm snow buried a layer of surface hoar and snowpack tests now indicate a poor bond between the layers. However, the dominant feature of the Rockies snowpack continues to be the extremely weak layers of facets and depth hoar at the base of the snowpack. Completely unpredictable at best, this weak base can be triggered very easily by humans. AVALANCHES: Numerous small avalanches have been triggered by skiers and explosives, failing either just under the recent storm snow or in the facets at the base of the snowpack. The exception to this is in the Fernie area, where greater volumes of snow have meant larger avalanches being triggered under similar conditions. FORECAST OF AVALANCHE DANGER UP TO THURSDAY EVENING (FEB 8) ALPINE - Considerable TREELINE ^Ö Considerable BELOW TREELINE ^Ö Moderate TRAVEL ADVISORY: A number of observers indicated significant cornice growth over the weekend, indicating that much wind transported snow has been moving around. This is an obvious indication that windslabs will be forming on leeward and cross loaded features. Cross loaded features can be particularly tricky as weakness^Ò on the shallow side of the slope can propagate across to deeper areas, creating large volume avalanches.