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Avalanche Forecast

Archived

Mar 12th, 2022–Mar 13th, 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 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

North Rockies.

Numerous natural and human triggered storm slab avalanches were reported on Saturday. The storm slabs were most reactive on wind-loaded slopes and were failing on a weak layer of surface hoar

Choose conservative terrain and avoid wind-loaded slopes on Sunday.

Confidence

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

Weather Forecast

SATURDAY NIGHT: Clearing skies / Light west winds / Low of -12 / Freezing level surface.

SUNDAY: Mix of sun and cloud, then 5-10 cm overnight / Light southwest wind / High of -5 / Freezing level valley bottom.

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

TUESDAY: Flurries; 5-10 cm / Moderate southwest wind / High of 1 / Freezing level 1500 m.

Avalanche Summary

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.

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

Snowpack Summary

10-20 cm of new snow and moderate southwest winds on Friday night formed fresh storm slabs that will be most reactive in wind affected terrain, especially where the recent snow is sitting on a weak layer of surface hoar.

The 20-25 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.
  • Be especially cautious as you transition into wind affected terrain.
  • Avoid freshly wind loaded features, especially near ridge crests, roll-overs and in steep terrain.

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.