Avalanche Danger is expected to quickly drop with cooling over the weekend but there may still be lingering problems. Give the snowpack time to cool down before venturing into complex terrain.
Summary
Confidence
Moderate
Weather Forecast
Increased cloud will develop throughout Sunday with 10cm of new snow expected between Sunday night and Monday morning. Generally overcast skies and light flurries are expected on Monday although an intense frontal system will bring heavy snowfall (over 40cm) to the region on Tuesday. Ridgetop winds should remain moderate from the south west for the forecast period. Freezing levels should sit at 1400m on Sunday, 1500m on Monday and 1200m on Tuesday.
Avalanche Summary
Over the past week, warming has triggered loose wet, cornice and persistent slab avalanches to size 2.5 on a variety of aspects and elevations. Conditions likely improved quickly with Saturday's drop in temperature, but there has been so much heat added to the snowpack over the last few days that some of the deep persistent weak layers may remain reactive for a few days. Once the snow surface develops a widespread supportive crust layer, it will become unlikely to trigger any deep weaknesses. Lingering cornices may remain reactive to human-triggering until there has been substantial cooling.
Snowpack Summary
Over the last couple days, the snow surface has been developing a weak crust overnight which has been quickly breaking down in the morning due to the warm temperatures. With the freezing levels dropping substantially Friday overnight, a more substantial crust has formed and is not expected to fully break down. If the crust remains supportive, it is expected to cap any deeper weaknesses. The warm temperatures and sun over the last week have woken up deeply buried weak layers within the snowpack. This includes a weak crust/surface hoar layer which was buried down 30-40cm in the north of the region, a widespread crust/facet layer buried in early February down around 1m, a lingering surface hoar layer from January down over a meter, and weak basal facets at the bottom of the snowpack. These old weak layers may still have isolated potential to produce large avalanches over the weekend, especially with a large trigger such as a cornice fall. Once the snowpack has seen substantial cooling, these layers are expected become inactive.
jlammers,
Avalanche Canada
