Avalanche Forecast
Sea To Sky
Overcast skies and isolated flurries will limit the effects of the strong late-winter sun, but you should remain wary of solar aspects where the new snow rests on a buried sun crust that may remain sensitive to human triggering.
Avalanche Problem 1: Storm Slabs
What Elevation?
Which Slopes?
Chances of Avalanches?
Expected Size?
Travel and Terrain Advice
- Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.
- Caution with south facing slopes, brief periods of sun could initiate avalanche activity.
- Start with simple terrain and slowly step out as you gather information about the new snow.
Avalanche Problem 2: Cornices
What Elevation?
Which Slopes?
Chances of Avalanches?
Expected Size?
Continued snowfall and strong wind from around the clock has formed large cornices on many ridgelines. Cornices are inherently unstable, unpredictable, and demand respect, especially when the sun is out.
Travel and Terrain Advice
- Firm cornices may pull back into flat terrain at ridgetop if they fail.
- Give cornices a wide berth when traveling on or below ridges.
- Avoid slopes when the solar radiation is strong, especially if they have large cornices overhead.
Avalanche Summary
A few human triggered avalanches to size 2.5 were reported Friday. A size 1.5 and second size 2.5 were triggered on southwest facing slopes between 1900 and 2000 m. These likely failed on the February 22nd interface which presents as a crust with surface hoar and/or facets on it. South facing slopes may be where this interface is most reactive. A skier also remote triggered a size 1.5 avalanche on a wind loaded slope of unknown aspect/elevation.
On Thursday natural avalanches to size 2.5 were reported on a variety of aspects as the snowpack adjusted to the new snow. Control work produced numerous storm slab and cornice failure avalanches to size 2 on all aspects.
On Wednesday soft wind slabs up to 20 in depth were sensitive to human triggering to size 1.5. Wednesday night's storm likely initiated a cycle of natural storm slab avalanche activity.
We received a great MIN report on Tuesday of a large snowmobile triggered wind slab avalanche on the Brandywine Glacier that featured a 100 cm crown. More details available here.
Snowpack Summary
The Wednesday night storm produced far more snow than expected, 20 to 45 cm of slightly upside down snow fell across the region accompanied by winds out of the east, southeast and south. In wind exposed terrain the new snow rests on widespread wind damaged snow and wind slabs. In wind sheltered terrain the new snow may be sitting on a thin layer of surface hoar.
The February 22nd interface is now down 50 to 70 cm, this layer is composed of old wind slabs, spotty surface hoar, facets and a sun crust on solar aspects. Snowpack testing on Thursday continues to produce planar shears at this interface. As we move into the later half of the weekend south facing slopes will be the most suspect with regard to this layer. Beneath the February 22nd interface the snowpack is well settled and strong.
Variable winds in the past month have produced cornices on many ridgelines. They will become touchier as they grow in size, as temperatures rise, and when they are subject to the strong late-winter sun on clear days.
Weather Forecast
The forecast has changed since yesterday. Sunday looks to be cloudy with a chance of flurries for the Sea to Sky region. Monday also looks cloudy, but clouds may give way to clear skies on Tuesday.
SUNDAY: Overcast, freezing level rising to around 600 m, light southwest wind, 1 to 5 cm of snow possible.
MONDAY: Scattered cloud cover in the morning, increasing cloud throughout the day, freezing level rising to around 700 m, light west/southwest wind, trace of snow possible.
TUESDAY: Clear skies, freezing level rising to around 1000 m, light variable wind, no snow expected.
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20 to 45 cm of recent snowfall arrived with strong wind. This slab is gaining strength and settling out quickly, but you should remain wary of south facing slopes where the new snow sits on a buried sun crust that is not worthy of your trust.