March 18, 2002 Canadian Avalanche Association Bulletin NORTH COLUMBIA REGION WEATHER: It's still wintery in the North Columbias with lows in the -20's and highs around -10 at treeline, although warm temperatures have been noted at very low elevations. Light to moderate northerly winds accompanied snowfalls of up to 30cm over the weekend. For this week we can expect flurries with some wind to continue as weak troughs move over the region, with more snow forecast the further south we go. There is potential for a warming trend starting Wednesday or Thursday. SNOWPACK: The main features now are windslabs, which have formed at treeline and in the alpine within the most recent storm snow. All areas are reporting this although they are most prevalent and reactive in the northernmost Cariboos such as the McBride area. These slabs have been formed by northerly winds and have loaded areas that are normally thinner and perhaps facetted or have suncrusts. The buried suncrusts, up to a meter down, have produced the largest avalanches of the past few days. We can also expect more recent suncrusts to have formed below 1200 meters that will be buried by the coming light snowfalls. AVALANCHES: Numerous natural and human-triggered windslabs were reported over the weekend at and above treeline, mostly size 1 with a few size 2 to 3. The largest ones ran on suncrusts on solar aspects. FORECAST OF AVALANCHE DANGER UP TO THURSDAY EVENING (MARCH 21) ALPINE - Considerable. TREELINE - Considerable. BELOW TREELINE - Low. TRAVEL ADVISORY: Use caution in lee and crossloaded areas. Remember, windloading may be "backwards" with the northerly winds. Probe and dig to find the buried suncrusts. SOUTH COLUMBIA REGION WEATHER: Spotty precipitation has occurred over the past several days with accumulations up to 30cm in some areas. Winds have been light from the southwest and temperatures warmer than elsewhere in the province (generally -5 to -15). Approaching frontal systems are expected to give more snow to this region than elsewhere, up to 20cm early in the week, and temperatures should rise to normal values mid-week. SNOWPACK: As in other regions, surface windslabs are the main concern. These windslabs are a bit more variable in this region due to less consistent winds. The snowfall amounts have been greater here than in the North Columbia over the past week so the slabs can be expected to be thicker where you do find them. Suncrusts buried by the snow last week are also a concern although again their distribution is variable. Deeper in the snowpack, February surface hoar layers seem to have settled out but a rain crust at low elevations was still giving isolated whumphs and avalanches last week. AVALANCHES: A few windslabs, mostly size 1 with a couple size 2^Òs, were reported over the weekend, triggered by ski cutting and explosives. FORECAST OF AVALANCHE DANGER UP TO THURSDAY EVENING (MARCH 21) ALPINE - Moderate, trending to Considerable with forecast snowfall. TREELINE - Moderate, trending to Considerable with forecast snowfall. BELOW TREELINE - Low. TRAVEL ADVISORY: With the variability we are seeing it's important to gather as much local information as possible by talking to locals and by making your own observations in the field.