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Avalanche Forecast

Archived

Mar 13th, 2022–Mar 14th, 2022

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.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

North Rockies.

Recently formed storm slabs will likely be reactive to human triggers on Monday; especially in wind affected terrain.

Riders may be surprised by widely propagating avalanches at treeline and below where storm slabs are sitting on a weak layer of surface hoar.

Confidence

Moderate - Uncertainty is due to the limited number of field observations.

Weather Forecast

SUNDAY NIGHT: Snow; 5-10 cm / Moderate southwest winds / Low of -8 / Freezing level surface.

MONDAY: Mix of sun and cloud with isolated flurries; 0-5 cm, and another 3-10 cm overnight / Strong southwest wind / High of 1 / Freezing level rising to 1600 m.

TUESDAY: Mix of sun and cloud with isolated flurries; 3-5 cm / Moderate west wind / High of 1 / Freezing level 1500 m.

WEDNESDAY: Mix of sun and cloud / Moderate west wind / High of -1 / Freezing level 1400 m.

Avalanche Summary

A few sledder triggered storm slab avalanches up to size 2 were reported in the Renshaw area on Sunday. The storm slabs were failing on a weak layer of surface hoar down 25-40 cm.

Numerous natural and human triggered storm slab avalanches up to size 2 were reported on Saturday near Pine Pass. The storm slabs were most reactive on wind loaded, north-east aspects and were failing on a weak layer of surface hoar down 25-50 cm. See MIN reports.

Riders may be surprised by widely propagating storm slabs that are sitting on a weak layer of surface hoar.

Snowpack Summary

15-25 cm of recent snow and moderate southwest winds formed fresh storm slabs that have been most reactive in wind affected terrain, especially where the recent snow is sitting on a weak layer of surface hoar.

The 15-25 cm of recent snow is sitting on a variety of surfaces including hard wind affected snow, sun crusts on southerly slopes, and surface hoar on shady or sheltered slopes. Expect storm slabs to be most reactive where they are sitting on either a sun crust or surface hoar.

The mid and lower snowpack is generally well-settled and strong in most areas, with multiple crusts throughout. No recent persistent slab avalanches have been reported on these layers.

Terrain and Travel

  • Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
  • Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
  • Avoid freshly wind loaded features, especially near ridge crests, roll-overs and in steep terrain.
  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • Back off slopes as the surface becomes moist or wet with rising temperatures.

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.