Avalanche Forecast

Archived

Jan 11th, 2021–Jan 12th, 2021

Alpine

Natural and human triggered avalanches likely.

Treeline

Natural and human triggered avalanches likely.

Below Treeline

Natural avalanches possible, human triggered probable.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

South Coast.

Natural avalanches are expected on Tuesday with reactive storm slabs at higher elevations above the rain/snow line and loose wet avalanches below. Travel in avalanche terrain is not recommended.

Confidence

Moderate - Forecast precipitation (either snow or rain) amounts are uncertain. We are confident the likelihood of avalanche will increase with the arrival of the forecast weather.

Weather Forecast

Yet another strong Pacific frontal system is slated to hit the Coastal regions tonight and persist until Wednesday morning bringing rising freezing levels, heavy precipitation, and strong to extreme wind.

Monday Night: 20 – 30 mm of rain/snow with freezing levels near 1400 m. Ridgetop wind strong from the southeast.

Tuesday: 25-45 mm of rain/ snow (only on the highest peaks) with forecast freezing levels 2000 m. Ridgetop wind strong-extreme from the South.

Wednesday: Generally a drying and cooling trend bringing a mix of sun and cloud, light southwesterly wind, and freezing levels near 900 m.

Avalanche Summary

Natural avalanche activity will likely be the theme on Tuesday during and after the storm, with loose wet activity below the snow-rain line and storm and wind slab activity above.

Snowpack Summary

60-80 mm of precipitation is forecast to accumulate Monday night through to early Wednesday morning, with it falling as snow above around 1700 m and rain below. This means that only the highest peaks will receive snow.

Above the snow-rain line, storm and wind slabs are expected to rapidly form and be reactive. Below the snow-rain line, wet loose avalanches will likely occur on all aspects. This is a significant amount of precipitation that will dramatically weaken the snowpack creating avalanches on Tuesday. This is a good time to wait out the storm and let the snowpack adapt, adjust, and strengthen before heading out into the backcountry.

The remainder of the snowpack is well-consolidated.

Terrain and Travel

Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.
Travel in alpine terrain is not recommended.
Watch for unstable snow on specific terrain features, especially when the snow is moist or wet.
The more the snow feels like a slurpy, the more likely loose wet avalanches will become.

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.

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.