April 4, 2003 SOUTH COAST REGION WEATHER: Unsettled weather continues to predominate on the Coast with flurries, including moderate southwest winds and temperatures remaining relatively cool, with highs of only ^Ö5 at treeline elevations. Although we^Òll see a few more sunny breaks over the weekend, we can still expect occasional flurries and gusty winds. SNOWPACK: The March 31 rain crust that formed below 2000m now lies under 15-50cm of snow. The storm snow is generally bonding well to the crust but soft windslabs can be found near ridge crests in the alpine and at treeline. Daytime heating in the form of solar radiation is causing the new snow and windslabs to weaken and surface instabilities can be expected as a result, especially on sunny aspects. The March 8 facet layer have been reactive to moderate shovel tests in the north. Cornices are large and overhanging in all areas. AVALANCHES: Most activity has been limited to size 1 surface slabs and loose snow slides, triggered by daytime warming. The exceptions were the 2 size 3^Òs noted above, reported in the Bridge River area. Solar radiation is suspected to be the cause of these deep slab failures in northern areas, with a slab failing right on glacier ice in steep terrain and another thick slab failing on an unknown deep layer. FORECAST OF AVALANCHE DANGER UP TO MONDAY EVENING (APRIL 7) ALPINE ^Ö Moderate, deteriorating to Considerable with daytime warming TREELINE - Moderate BELOW TREELINE - Moderate TRAVEL ADVISORY: It^Òs all about temperatures at this time of year. Keep a careful eye on how the sun is affecting the surface layers. When they start to get wet and weak it^Òs time to modify your terrain choices and stay away from steep, sunny aspects. NORTH COLUMBIA REGION WEATHER: Unsettled spring flurry activity has continued, with 10-30cm falling over the past few days. Winds have been light and temperatures have remained just on the cold side of the freezing mark. Although a weak ridge will build into the weekend expect unsettled conditions to prevail, including convective flurry activity. Temperatures will warm with the advance of the next system on Monday. SNOWPACK: Temperatures have cooled enough and for long enough to have created supportive crusts at the March 31 interface at elevations below 2200m. These crusts are now buried by up to 50cm of storm snow (less at lower elevations). In the alpine and at treeline some soft windslabs can be found near ridge crests. Solar radiation causing the storm snow layers to weaken is the primary consideration at the moment, but several deeply buried persistent weaknesses remain a significant danger as well. A smaller surface avalanche or a cornice fall could trigger such a weakness and cause a very large avalanche to run to valley bottom. AVALANCHES: Solar radiation has caused numerous size 1-2 surface slab and loose snow avalanches to run the past few days. Some areas have seen larger avalanches up to size 3 failing in storm snow layers. FORECAST OF AVALANCHE DANGER UP TO MONDAY EVENING (APRIL 7) ALPINE ^Ö Considerable, deteriorating to High with daytime warming TREELINE ^Ö Moderate, deteriorating to High with daytime warming BELOW TREELINE ^Ö Moderate, deteriorating to Considerable with daytime warming TRAVEL ADVISORY: Temperatures are the issue right now and it^Òs important to monitor how daytime warming is causing the snow to weaken. Keep looking above you to ensure that slopes and cornices above are not being cooked by the sun more than you are in the valley bottom shade. SOUTH COLUMBIA REGION WEATHER: Spring flurries continue to be the story, with 20-40cm of snow accumulating over the past 5 days. Winds have been light and freezing levels are just above valley bottoms. A slight drying trend is expected over the weekend but occasional cloudy periods and flurries will continue regardless. With the advent of a southwest flow on Monday temperatures will become warmer. SNOWPACK: Below 2200m supporting crusts have formed where the previous surface had been rain-soaked. The new snow layers are bonding well to these crusts when temperatures are cool. As the day warms this bond breaks down. In the alpine and at treeline there are some soft windslabs near ridge crests. Daytime warming has caused surface instabilities in the alpine as well, especially on solar aspects. In all areas there continues to be a concern that deeply buried weak layers will fail with significant warming or with the weight of a surface avalanche or cornice drop. AVALANCHES: After several large avalanches earlier in the week, activity has been limited to surface instabilities triggered by daytime warming, generally size 1, for the latter part of the week. FORECAST OF AVALANCHE DANGER UP TO MONDAY EVENING (APRIL 7) ALPINE ^Ö Considerable, deteriorating to High with daytime warming TREELINE ^Ö Moderate, deteriorating to High with daytime warming BELOW TREELINE - Moderate, deteriorating to Considerable with daytime warming TRAVEL ADVISORY: Although air temperatures have remained relatively cool, daytime warming continues to be a concern in the form of solar radiation. This type of warming affects steep southerly slopes and rocky areas most. Stay vigilant when in and beneath this sort of terrain. KOOTENAY BOUNDARY REGION WEATHER: Winds have been light and temperatures have been remaining cool. Variable snow amounts continue to accumulate with unstable flurry activity. A weak ridge will build over the weekend but occasional convective flurries will continue. Temperatures will warm on Monday with the advent of a southwest flow. SNOWPACK: Soft windslabs can be found in the alpine and at treeline in the lee of ridges. Daytime warming is causing the surface snow to weaken at these elevations, especially on steep southerly slopes. Below treeline a series of crusts are holding the snowpack together and temperatures have not been warm enough to break these crusts down significantly. Cornices are large and fragile. AVALANCHES: Size 1 sluffing has been reported on steep south aspects. FORECAST OF AVALANCHE DANGER UP TO MONDAY EVENING (APRIL 7) ALPINE ^Ö Considerable, deteriorating to High with daytime warming TREELINE ^Ö Moderate, deteriorating to Considerable with daytime warming BELOW TREELINE ^Ö Low, deteriorating to Considerable with daytime warming TRAVEL ADVISORY: Solar radiation is the destabilizing factor right now. Even with cool air temperatures, steep southerly slopes can gain a lot of heat during the day. Surface snow layers and cornices can be significantly weakened with this warming and create a hazard on an otherwise cool day. Watch for the snow surface to become wet and heavy and keep a look out for the same happening on slopes above you, as this will signal rising danger. SOUTH ROCKIES REGION WEATHER: Unstable spring flurry activity continues, leaving 20-30cm of fresh snow amid moderate southwest winds and reasonably cool temperatures hovering around the freezing mark at valley bottom. We can expect much of the same until Monday when more sun and warming temperatures are forecast. SNOWPACK: Cooling has finally come to Fernie and this has allowed supportive crusts to form below 2000m at the March 31 interface, where the old surface had been saturated by the rain last weekend. The new snow now overlies these crusts and is generally bonding well until the afternoons, when daytime heating is causing some instabilities to develop. Isolated soft windslabs can be found in lee areas above 2000m. Deeply buried weak layers remain a concern, especially on the BC side of the divide. Cornice falls or surface snow avalanches could trigger a deep instability, particularly on a warm day. AVALANCHES: Warm temperatures and human activity mid week have triggered loose, wet surface avalanches and some soft windslabs. They have generally been size 1. FORECAST OF AVALANCHE DANGER UP TO MONDAY EVENING (APRIL 7) ALPINE ^Ö Considerable, deteriorating to High with daytime warming TREELINE ^Ö Moderate, deteriorating to High with daytime warming BELOW TREELINE ^Ö Moderate, deteriorating to Considerable with daytime warming TRAVEL ADVISORY: Temperatures are the key right now. When solar radiation affects southerly slopes expect the surface layers to weaken and begin to avalanche naturally in the form of sluffs or slabs. Cornices can also be weakened and fall off. Watch for this warming to affect the snowpack even on a cloudy day next week with higher freezing levels caused by a warmer airmass. Temperatures remaining above zero overnight will signal rising snowpack temperatures, leading to increased danger levels.