Avalanche Forecast
North Columbia
Where there is uncertainty in the snowpack, conservative terrain is the answer.
Check out today's Forecaster's blog for tips on managing the spatial variability associated with our current persistent slab problem. LINK
Avalanche Problem 1: Wind Slabs
What Elevation?
Which Slopes?
Chances of Avalanches?
Expected Size?
Travel and Terrain Advice
- Be aware of areas that have been reverse loaded by winds
- Use ridges or ribs to avoid pockets of wind loaded snow.
Avalanche Problem 2: Persistent Slabs
What Elevation?
Which Slopes?
Chances of Avalanches?
Expected Size?
Reactivity at the buried December 15 interface will likely be greater where the new snow has settled into a cohesive slab above buried surface hoar. Use extra caution in wind affected areas and around steeper, sheltered slopes at treeline and below.
Travel and Terrain Advice
- Use conservative route selection, choose moderate angled and supported terrain with low consequence.
- Watch for whumpfing, shooting cracks, or signs of recent natural avalanches.
Avalanche Summary
Reports from the past few days include several natural storm and wind slab avalanches to size 2.5 in the alpine and tree line. There have also been a few reports of skier accidental and remote (triggered from a distance) avalanches from size 1.5-2 below tree line. These avalanches are failing at the interface between the recent storm snow and the old snow surface.
Slab avalanche activity can be expected to persist or possibly increase as our recent snow consolidates into a slab above the range of weak surfaces present at the December 15 interface. In areas where new snow has not yet consolidated into a slab, expect continued potential for triggering loose dry avalanches in steep terrain.
Snowpack Summary
Stormy weather over the past week has brought 40-60cm of new snow to the region. The new snow lies over a wide variety of old surfaces, including large surface hoar (weak, feather-like crystals), hard crusts formed by sun or wind, and sugary facets. The bond at this old snow interface becomes critical as the overlying snow gradually consolidates into a slab. The most concerning areas areas will be those that have seen previous surface hoar development, such as sheltered areas at and below tree line and sheltered northerly aspects in the alpine. Additionally, any steep solar aspects where surface hoar may be sitting on sun crust should be considered areas where this weak layer may be more likely to trigger.
A crust which was formed by rain in late November is a major feature in the snowpack and is down approximately 80-110cm at tree line elevations. Snowpack tests suggest the snow above is currently bonding well to it.
Snowpack depth decreases rapidly below tree line. Look out for early season hazards such as rocks, stumps, and open creeks.
Weather Forecast
Saturday: A mix of sun and cloud. Light to moderate northwest winds. Alpine temperature of -15.
Sunday: Mainly sunny. Light variable winds. Alpine temperature of -13.
Monday: A mix of sun and cloud. Light variable winds. Alpine temperature of -17.
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Shifting winds since the storm have been redistributing new snow into wind slabs on a variety of aspects. The most recent of these are the result of Friday's north to northeast winds. Keep this reverse loading pattern in mind as you gain elevation.