Avalanche Forecast

Archived

Dec 24th, 2018–Dec 25th, 2018

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

Jasper.

Play safe and give yourselves lots of time to return home early for some Christmas cheer. Merry Christmas one and all. (TT)

Weather Forecast

Little change expected in over the holidays, forecasted winds will tamper Sunday night as a SW flow will settle in for the next few days. Temperatures will remain cool with daytime alpine highs of -10. Inversions can be expected with slightly warmer temps in the alpine.A detailed mountain weather forecast is available from Avalanche Canada.

Snowpack Summary

Moderate to strong south west winds continue to load lee slopes at tree line and above. The Dec. 11th persistent weak layer has been buried 50 to 100cm and is ripe for human triggering. The deep persistent weakness lingers near the ground in the depth hoar and facets.

Avalanche Summary

Recent avalanche control (Dec 21) produced consistent size 2-2.5 avalanches running to roadside. Previous to the control work, a large natural avalanche cycle occurred primarily failing on the Dec 11 weak layer. Most notably is a large, possibly cornice triggered size 3.5, which ran nearly full run out, on the Churchill (north and south) paths.

Confidence

Due to the number of field observations

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.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

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.