A special warning has been issued for the substantial warming and sun this week. Deeply buried weaknesses within the snowpack are expected to wake-up and produce very large avalanches. It is best to avoid avalanche terrain during the heat of the day.
Summary
Confidence
Moderate
Weather Forecast
The ridge of high pressure is expected to break down on Friday as a weak frontal system reaches the coast. Friday should be sunny with alpine winds progressively becoming strong from the southwest and freezing levels progressively falling below 2000m. Cloudy conditions are expected for Saturday with moderate to strong southwest winds in the alpine and freezing levels dropping below 1500m. Light scattered flurries are possible on Saturday. A mix of sun and cloud is expected for Sunday with light to moderate southerly winds in the alpine and afternoon freezing levels around 1400m. A more substantial storm system is currently expected to arrive Sunday night.
Avalanche Summary
On Wednesday, numerous slabs up to size 2.5 were reported on solar aspects in the far north of the region. Some of these releases were over 2m deep on old weak layers. In the south, the activity consisted of loose wet avalanches up to size 2.5 and cornice releases up to size 2.5. THe cornice releases were not triggering slabs in the southern part of the region. On Tuesday, a skier triggered a size 1.5 wet slab avalanche on a steep roll on an east aspect at 1400m elevation. The slab was 10-30cm thick and slide on a crust. A natural size 3.5 was reported north of Stewart on a north aspect at 2200m. This was 3-4m thick and failed on the ground on a steep glaciated feature. Numerous natural cornice failures and loose wet avalanches were reported up to size 2. The continued warming, sun exposure, and limited overnight recovery means natural cornice releases, deep persistent slab releases, and loose sluffing are expected to continue on Friday. Very large avalanches will remain a serious concern until the region gets some sustained periods of cooling,
Snowpack Summary
A supportive crust was reported on on all aspects to mountaintop in the south of the region on Thursday morning. This crust is expected to have quickly broken down during the day. In the north of the region, no surface crust formed overnight. On Wednesday, moist surface snow was being reported to mountain tops on all aspects with wet surface snow below 1500m. A weak crust/surface hoar layer which was buried over a week ago is down 30-40cm in the north of the region. A widespread crust/facet layer buried in early February and a lingering surface hoar layer from January can now be found down over a meter. These old weak layers still have the potential to produce large avalanches, especially with a large trigger such as a cornice fall. Extra caution is required during this period of substantial warming and intense solar radiation, as this is when these layers have the biggest potential to wake up.
rbuhler,
Avalanche Canada
