Avalanche Forecast

Moderate - Uncertainty is due to the track & intensity of the incoming weather system.

FRIDAY NIGHT- Snow, 10-20 cm / southwest wind, 30-60 km/h / alpine high temperature near -6

SATURDAY - Snow and flurries, 5-10 cm / southwest wind, 25-55 km/h / alpine high temperature near -5 / Freezing level rising to 1000 m

SUNDAY - Snow, 15-30 cm / southwest wind, 20-50 km/h / alpine high temperature near -3 / Freezing level 1500 m

MONDAY - Snow and flurries, 5-15 cm / southwest wind, 20-40 km/h / alpine high temperature near -10

Storm and wind slabs were reactive underfoot/sled on Thursday. Wind slabs to size 2 were observed at upper elevations in lee terrain, with depths 40-60 cm. A size 1.5 storm slab avalanche was reported failing naturally on the early December crust, with good propagation. Explosives triggered avalanches to size 2 along ridgelines, again being reported with good propagation. 

A handful of MIN reports (thank you!!) from the Gorge found a highly reactive snowpack including a remotely triggered avalanche with surprising propagation from about 20 m away (here).

On Wednesday, small storm and wind slabs showed reactivity on predictable, loaded features and failing on the Dec 7 surface hoar/crust. Explosives and skiers triggered size 1-1.5 slab avalanches on leeward aspects above 2000 m. And loose, dry sluffing was easy to initiate in steep terrain. With the most reactivity, a small (size 1) avalanche was triggered remotely by a vehicle traveling along an exposed ridgeline. 

On Tuesday, several small (size 1-1.5) loose dry avalanches were reactive to skier traffic. Storm slab avalanches were triggered by explosives and skier traffic on East, North, and West aspects above 2000 m; average depth 5-25 cm. 

Ongoing flurries and snow has accumulated 20-50 cm fresh snow around the region. This new snow has buried a weak layer of surface hoar in many areas. This new snow combined with southwest winds has formed reactive slabs, especially at higher elevations. 

A weak layer that was buried in early December is now down 40-60 cm. This layer is variable and has been reported to exist as either a crust or surface hoar. In any case, it is a persistent weak layer with a significant load above it now, and it may react easily to human triggers.

Another crust that was buried in early November can be found near the base of the snowpack. There have been no recent avalanches reported on this layer, however it may be possible to trigger it from shallow, rocky terrain.

• Choose conservative terrain and watch for clues of instability.
• Avoid freshly wind loaded terrain features.
• Look for signs of instability: whumphing, hollow sounds, shooting cracks, and recent avalanches.
• As the storm slab problem gets trickier, the easy solution is to choose more conservative terrain.