Avalanche Forecast

Issued: Dec 26th, 2019 4:00PM

The alpine rating is considerable, the treeline rating is moderate, and the below treeline rating is moderate.

Avalanche Canada shorton, Avalanche Canada

The snowpack is gradually gaining strength, but it is still possible to trigger very large avalanches. Avoid steep, rocky, wind-affected terrain.

Summary

Confidence

Moderate - Uncertainty is due to the fact that deep persistent slabs are particularly difficult to forecast.

Weather Forecast

THURSDAY NIGHT: Mostly cloudy, 40 km/h wind from the southwest, alpine temperatures drop to -12 C.

FRIDAY: Cloudy with isolated flurries in the morning bringing up to 5 cm of snow then some sunny breaks in the afternoon, 30 km/h wind from the west, alpine high temperatures around -8 C.

SATURDAY: Mix of sun and cloud, 10-20 km/h wind from the west, alpine high temperatures around -10 C.

SUNDAY: Cloudy with some light flurries, 20-30 km/h wind from the north, alpine high temperatures around -8 C.

Avalanche Summary

Avalanche activity is on the decline following the intense storm and avalanche cycle last weekend. During the storm very large (size 3) avalanches occurred naturally and with explosive triggers. On Monday and Tuesday more large avalanches (size 2-2.5) were triggered with explosives, and then on Wednesday and Thursday only small (size 1-1.5) avalanches were reported. Some smaller (size 1) wind slab avalanches have been triggered by riders over the past few days.

While the likelihood of triggering a deep persistent slab avalanche is on the decline, there is still a fair bit of uncertainty about this problem, and the consequences of triggering such a large avalanche are severe.

Snowpack Summary

Fresh wind slabs are forming at higher elevations while sheltered areas have 10-30 cm of low density snow. The loose snow overlies a hard rain crust below 1700 m. Weak snow and decomposing crust layers can be found near the bottom of the snowpack (80-140 cm below the surface). Intense loading from last weekend's storm resulted in very large (size 3) avalanches on these layers. Although the strength of these layers has improved to some degree since then, a complex deep persistent slab avalanche problem persist (check out latest forecaster blog here).

Terrain and Travel

  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
  • Cornice failure may trigger large avalanches.
  • Minimize exposure to overhead avalanche terrain, large avalanches may reach the end of runout zones.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.

Valid until: Dec 27th, 2019 4:00PM