Avalanche Forecast
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.
Avalanche Problems
Storm Slabs
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.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Possible - Likely
Expected Size: 1 - 2.5
Loose Wet
Sunny skies and rising freezing levels will likely trigger a wet loose natural avalanche cycle on Monday within the new snow.
Back off slopes as the surface becomes moist or wet with rising temperatures.
Aspects: East, South East, South, South West, West.
Elevations: All elevations.
Likelihood: Likely - Very Likely
Expected Size: 1 - 1.5