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Avalanche Forecast

Archived

Nov 26th, 2018–Nov 27th, 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

South Columbia.

Avalanche hazard will increase through the storm. If snowfall amounts exceed 25 cm, avalanche hazard will be higher than indicated.

Confidence

Low - Forecast snowfall amounts are uncertain

Weather Forecast

Snow forecasts identify the largest snowfall amounts occurring in the north and east of the South Columbia forecast region.MONDAY NIGHT: Flurries / Accumulation: 5-15 cm / Alpine temperature: High 0C / Moderate southwest ridge wind / Freezing level 1600mTUESDAY: Periods of snow / Accumulation: 5-20 cm / Alpine temperature: High -1C / Moderate southwest ridge wind / Freezing level 1500mWEDNESDAY: Cloudy with flurries / Accumulation: up to 10 cm / Alpine temperature: High -2C / Light to moderate southwest ridge wind / Freezing level 1400mTHURSDAY: Mainly cloudy with isolated flurries / Accumulation up to 5 cm / Alpine temperature: High -4C / Light southwest wind / Freezing level 1200m

Avalanche Summary

On Saturday, a large human triggered avalanche was reported on Meadow Mountain. The size 3 avalanche occurred on a steep, north aspect in the alpine and failed to ground, likely on a crust buried in October. Find the MIN report here.Earlier in the month, a natural avalanche cycle took place over the late October crust/facet combination. Be aware of the continued possibility for smaller avalanches to 'step down' or even initiate at this deeper layer. It exists primarily in the alpine.

Snowpack Summary

Snowfall through Monday afternoon has deposited 5-15 cm new snow around the region. Two layers, both consisting of a crust and weak surface hoar, are now buried down 30-40 cm and 45-60 cm respectively. Near the ground, sugary, faceted snow and crust buried late October supports the snowpack. The total snowpack depth varies from 110-160 cm in the alpine, with snowpack depth decreasing quickly with decreasing elevation.

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.

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.