Avalanche Forecast

Archived

Dec 27th, 2020–Dec 28th, 2020

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Regions

South Coast.

New snow is especially sensitive to seeing the sun for the first time. On Monday afternoon you may observe increased reactivity of storm slabs to human triggers as well as solar triggered point releases on steep south facing slopes.

Confidence

Moderate - Uncertainty is due to how quickly the snowpack will recover and gain strength.

Weather Forecast

Sunday night: Clearing, light southwest wind, freezing level rising to 1500 m.

Monday: Sunny, light northwest wind, treeline temperature 0 C, freezing level 1600 m.

Tuesday: Increasing cloud, moderate southwest wind, treeline temperature -3 C, freezing level 800 m.

Wednesday: Cloudy, moderate southwest wind, treeline temperature -3 C, freezing level 800 m.

Avalanche Summary

On Saturday, we received reports from the North Shore mountains of several skier controlled wet loose size 1 and a skier remote size 1 wet slab on a steep unsupported roll. Some whumphing was observed but very little propagation within the storm snow.

We know you're out there! Please share your observations with us on the Mountain Information Network (MIN)! Photos are especially helpful. Thanks for all the great MINs submitted so far.

Snowpack Summary

30-70 cm of recent snow appears to be adhering well to old surfaces. At higher elevations where dry snow fell, strong winds are expected to have deposited deep pockets of storm slab into lee terrain features.

Around 50-100 cm of snow now overlies a hard melt-freeze crust up to around 1500 m. This layer varies so widely in depth due to the wind transport of snow as it fell over the last two storms. It seems to be bonding well with surrounding snow.

The remainder of the snowpack is well-settled and hosts numerous other melt-freeze crusts which are well bonded to the surrounding snow.

Terrain and Travel

Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet
A moist or wet snow surface, pinwheeling and natural avalanches are all indicators of a weakening snowpack.
Be careful with wind loaded pockets, especially near ridge crests and roll-overs.

Problems

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.

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.