Avalanche Forecast
South Columbia
Avalanche danger will increase in the afternoon with strong solar input and warming temperatures. Concern for persistent slab problems is on the rise.
See the Forecaster's Blog for more: http://www.avalanche.ca/blogs/2018-03-09-first-big-warm-up
Avalanche Problem 1: Loose Wet
What Elevation?
Which Slopes?
Chances of Avalanches?
Expected Size?
Travel and Terrain Advice
- Avoid exposure to sunny slopes, especially in the afternoon.
- Be cautious of sluffing in steep terrain, particularly where the debris flows into terrain traps.
Avalanche Problem 2: Wind Slabs
What Elevation?
Which Slopes?
Chances of Avalanches?
Expected Size?
Wind slabs formed on all aspects during the recent storm and they may remain reactive on Monday. Extra caution is needed on solar aspects where sunshine could act as a natural trigger and buried sun crust as a sliding layer.
Travel and Terrain Advice
- Watch for wind loaded pockets near ridge crests and roll-overs.
- Use ridges or ribs to avoid pockets of wind loaded snow.
Avalanche Problem 3: Persistent Slabs
What Elevation?
Which Slopes?
Chances of Avalanches?
Expected Size?
Rising temperatures and strong sunshine are increasing concern for weak layers buried deep in the snowpack. In addition to human triggering in thin spots, solar warming and cornice releases are possible natural triggers for persistent slabs.
Travel and Terrain Advice
- Avoid steep convexities or areas with a thin or variable snowpack.
- Pay attention to overhead hazards like cornices which could trigger persistent slabs.
- Choose regroup spots away from avalanche paths.
Avalanche Summary
A widespread natural avalanche cycle to size 3 was reported on Saturday. These avalanches were primarily wet loose avalanches on sunny aspects, however, some storm slab avalanches and cornice failures were also noted.
Reports from Friday included numerous storm slabs and wind slabs ranging from size 1.5 to 2.5. These were triggered naturally as well as with ski cutting and all aspects and elevations were represented. See this MIN report for an example.
On Thursday a snowcat triggered a size 2 persistent slab that failed on the mid-January weak layer when its blade undercut a slope harbouring buried surface hoar.
Avalanche activity is expected to increase as we move into a period of intense sun and prolonged warming. Predictable loose wet avalanches from steep, sunny terrain should be easy to manage. The trickier problem will emerge as warmth penetrates into the snowpack to tickle deeper persistent weak layers. The next few days will be a time to avoid exposure to large sun-exposed features and keep well away from corniced slopes.
Snowpack Summary
15-25 cm of snow from Thursday into Friday sits on sun crusts on solar aspects and well-settled storm snow on more northerly aspects. Several other sun crust layers may be found within the older storm snow on solar aspects.
A couple of layers buried in mid-late February (down around 70-120 cm) are variably reactive, but both have the potential to create surprisingly large avalanches if triggered. Initially, these interfaces were most reactive on solar aspects, where they present as buried sun crusts. However, persistent slabs have been triggered on shady aspects too, where surface hoar and/or facets exist.
Deeper persistent weak layers from January and December are generally considered dormant, but could wake up with forecast warming, a surface avalanche stepping down, cornice fall, or a human trigger in a shallow or variable-depth snowpack area. These layers consist of sun crust, surface hoar and/or facets.
Weather Forecast
Sunny and warm until the start of our next weather system on Wednesday.
MONDAY: Sunny. Light southeast winds. Freezing level rising to 2200 metres with alpine high temperatures around +2.
TUESDAY: Mainly sunny. Light southeast winds, increasing over the day. Freezing level to 2500 metres with alpine high temperatures of +3.
WEDNESDAY: Cloudy with isolated flurries in the afternoon. Light south winds. Freezing level near 2000 metres with alpine high temperatures of +1.
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Wet loose avalanches are likely in steep, rocky, sunny terrain. Warming could also wake up more deeply buried weak layers, creating a surprisingly large avalanche.