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Avalanche Forecast

Archived

Nov 22nd, 2019–Nov 23rd, 2019

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

Regions

North Columbia.

Considerable alpine danger is based on storm snow totaling 20+ cm by Saturday afternoon which is expected to do two things:

1. Create a touchy storm slab problem.

2. Potentially wake up the persistent slab problem. 

Prepare for rapidly changing conditions and increasing hazard.

Confidence

Low - Forecast snowfall amounts are uncertain. Uncertainty is due to the limited number of field observations.

Weather Forecast

It’s late November and the weather pattern is bringing winter to the door this weekend. The region should get a nice re-fresh from the system.

FRIDAY NIGHT: 5 to 15 cm of snow possible with greater accumulations in the north of the region, freezing level holding around 1200 m, light to moderate southwest wind.

SATURDAY: Storm day, visibility is likely to be poor, freezing level around 1200 m, moderate west/southwest wind, 5 to 15 cm of snow possible, with another 10 to 20 cm possible Saturday night.

SUNDAY: Broken cloud cover, freezing level around 1300 m, moderate west wind, 1 to 5 cm of snow possible.

MONDAY: Broken cloud cover, freezing level near valley bottom, light northwest breeze, no significant snowfall expected.

Avalanche Summary

Very little recent avalanche activity has been reported, but times are changing this weekend. It's worth checking out this MIN report from a skier triggered avalanche in the neighboring Glacier Park Region on Monday. As storm snow totals begin to approach 20+ cm natural avalanche activity is likely.

Snowpack Summary

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.