Avalanche Forecast

Fair - Timing, track, or intensity of incoming weather system is uncertain

A warm storm hits the region on Saturday. Models are currently showing 15-30mm of precipitation but freezing levels are forecast to stay around 2000m during the day so much of it will fall as rain. Freezing levels are forecast to drop down to below 1000m by Sunday morning so the rain may switch to snow at the end of the storm. Alpine winds are forecast to be strong during the storm and ease by Sunday morning. On Sunday, a mix of sun and cloud is expected with freezing levels around 1000-1500m and light alpine winds. There is currently uncertainty regarding Sunday night and Monday. A second storm pulse may affect the region but it also has the potential to track too far to the south and completely miss the region.

On Tuesday through Thursday, several natural avalanches were reported to have released on the ground. These were on solar aspects and the largest were size 3. Natural and skier triggered wet sluffing was also reported up to size 2. On Thursday, several small wind slabs were triggered by skiers.  Saturday's storm is expected to quickly build touchy new wind slabs where the precipitation falls as snow.  At lower elevations where the precipitation falls as rain, loose wet avalanches can be expected.  The major question and my biggest concern is whether deeply buried persistent weaknesses will wake-up with the new loading. These persistent weak layers could have the potential to result in some very large persistent slab avalanches. However, this is probably a low probability, high consequence type of problem.

A moist snow surface has been reported to around 2500m on solar aspects and to around 2000m on north aspects. The mid-February crust is buried down 10-30 cm and there is a weak layer of facets and/or surface hoar in the sandwich above the crust. The mid pack is well settled with a couple of persistent weak layers that continue to give hard or very hard results in snow profile tests. The late-Jan crust/surface hoar layer (up to 100 cm deep) and the mid-January surface hoar (80-120 cm deep) have gained significant strength and have been dormant for several weeks but now have the potential to wake-up with the current warm temperatures and new loading. A basal weakness has recently become active with the warm conditions and several avalanches have released to the ground.