Avalanche Forecast

Archived

Nov 26th, 2015–Nov 27th, 2015

Alpine

Below Threshold.

Treeline

Below Threshold.

Below Treeline

Below Threshold.

Alpine

Below Threshold.

Treeline

Below Threshold.

Below Treeline

Below Threshold.

Alpine

Below Threshold.

Treeline

Below Threshold.

Below Treeline

Below Threshold.

Regions

Purcells.

Rising alpine temperatures up to +5c are in the forecast for the next few days. Use care venturing into big terrain at treeline and above. Consider sharing your observations through the Mountain Information Network MIN

Weather Forecast

An arctic high persists in the forecast region with no precipitation in the forecast for the next 4 days. An above freezing layer (AFL) is forecast to move into the region Friday with temperatures up to +5c between 1500 and 3000m. Skies should be sunny and clear at upper elevations with valley temperatures below freezing and the possibility of valley fog in the mornings dissipating in the afternoon.

Avalanche Summary

Reports from operators speak of low density size 1's failing on the Nov.23rd surface hoar layer now buried by 10 to 20cm of storm snow

Snowpack Summary

Monday's storm snow fell on a variety of old surfaces including crust, surface hoar and old settled snow. Arctic air moving into the region has resulted in northerly winds forming small wind slabs on south facing features near ridge top and t tree line. Warm temps and strong solar input formed a crust on south facing features which can be found underneath Monday's storm snow. There are at least three surface hoar layers in the snowpack buried on: Nov. 5th, Nov. 11th and Nov. 23rd. The first two have been largely unreactive. Facets may exist just above the ground on shaded slopes in the alpine. Rapid rising temperatures forecast for the next few days may change the snowpack dramatically.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.