Avalanche Forecast

Issued: Nov 25th, 2018 4:45PM

The alpine rating is considerable, the treeline rating is moderate, and the below treeline rating is low. Known problems include Storm Slabs and Deep Persistent Slabs.

kdevine, Avalanche Canada

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.

Summary

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

20-45 cm sits on a weak layer of surface hoar (feathery crystals) and sun crust. The likelihood of triggering this layer will increase with heavy snowfall, rising freezing levels and wind.

Be careful with wind loaded pockets, especially near ridge crests and roll-overs.Watch for signs of instability such as whumpfing, cracking, and recent avalanchesIf triggered, the storm slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 2

Deep Persistent Slabs

A crust at the base of the snowpack will result in large avalanches if triggered. Storm slab avalanches may have the potential to step down to this layer.

Pay attention to overhead hazards like cornices which could trigger the deep persistent slab.Minimize overhead exposure during periods of heavy loading from new snow, wind.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

2 - 3

Valid until: Nov 26th, 2018 2:00PM