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Avalanche Forecast

Archived

Nov 25th, 2018–Nov 26th, 2018

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
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.

Regions

North Columbia.

Warm, windy and (hopefully) snowy! The storm has arrived and forecast freezing levels and snowfall amounts are uncertain. Expect the hazard to increase during the day in areas experiencing heavy snowfall, above freezing temperatures or high winds.

Confidence

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

Weather Forecast

Significant snowfall amounts, rising freezing levels and moderate to strong winds are forecast to arrive Sunday night and continue into Tuesday. Forecast snowfall amounts vary throughout the region, with higher amounts predicted for the Monashees.SUNDAY NIGHT - Flurries, 5-10 cm / moderate southerly winds / freezing level 1000mMONDAY - Snow, 5-30 cm / moderate to strong southerly winds / freezing level 1500-2000mTUESDAY - Flurries, 5-20cm / moderate southerly winds / freezing level 1500mWEDNESDAY - Cloudy with sunny periods and isolated flurries, up to 5 cm / light to moderate southerly winds / freezing level 1500m

Avalanche Summary

There have been no new avalanches reported in the North Columbia, however a size 3 human triggered avalanche that likely ran on the October crust was reported on Saturday, November 24 in the South Columbia region. The avalanche reportedly occurred on a northwest aspect, on a lee feature in the alpine. The full report can be found on the Mountain Information network. Click here to read the report

Snowpack Summary

5-10 cm of snow overnight on Sunday night brings the recent storm snow amounts to 20-45 cm. This snow sits on a weak layer of surface hoar (feathery crystals) and sun crust on steep south facing slopes. The surface hoar is reportedly widespread at treeline and below; it is more sporadic in the alpine, however it may be found in wind sheltered areas. New snow, wind and warm temperatures throughout the day will increase the likelihood of triggering this layer. At the base of the snowpack there is a crust that formed in late October. There have been no reports of reactivity on this layer in the North Columbia region, however with strong winds and rising freezing levels, this layer could come into play during this storm. Storm slab avalanches may have the potential to trigger avalanches on this deeper layer.Total snowpack depths vary greatly with elevation. Recent reports show depths of 120-210cm in the alpine, 80-150 cm at treeline and 10-120 cm below treeline.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.