Avalanche Forecast
Regions: Northwest Inland.
Fresh snow and strong winds overnight and during the day will mean that storm slabs are expected to be reactive, and a natural avalanche cycle may occur. Human triggered avalanches are likely. Choose conservative terrain.
Confidence
Moderate - Forecast snowfall amounts are uncertain.
Weather Forecast
MONDAY NIGHT - Snow, 10-20 cm / southwest wind, 40-80 km/h / alpine low temperature near -8
TUESDAY- Flurries, 5-10 cm / southwest wind, 40-60 km/h / alpine high temperature near -7
WEDNESDAY - A mix of sun and cloud with isolated flurries / west wind, 20-40 km/h / alpine high temperature near -9
THURSDAY- A mix of sun and cloud / west wind, 20-30 km/h / alpine high temperature near -8
Avalanche Summary
Fresh snow and strong winds will promote widespread storm slab development, which will likely result in a natural avalanche cycle on Tuesday.
Last week there were reports of wind slab, persistent slab (failing on the February 19 surface hoar layer), and deep persistent slab (failing on basal facets) avalanches. This pattern highlights loading and surface avalanches from recent stormy weather straining multiple weak layers in the snowpack.
Snowpack Summary
With 10-20 cm of new snow on Monday night and another 5-10 cm expected on Tuesday accompanied by strong southwest winds, fresh storm slabs will likely be widespread.
Loading from new snow and wind has made several persistent weak layers problematic over the past week. A combination of surface hoar and sun crust layers were buried on February 19 and currently sit 30-60 cm below the surface that seem to be most sensitive to human triggering at treeline elevations.
A couple of weak layers that formed in January are buried in close proximity to one another 80-140 cm below the surface. Below that, an early season crust/facet layer lurks at the base of the snowpack.
Terrain and Travel
- Storm snow and wind is forming touchy slabs. Use caution in lee areas in the alpine and treeline.
- Storm slabs in motion may step down to deeper layers resulting in large avalanches.
- Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.
Avalanche Problems
Storm Slabs
Fresh snow and wind will promote widespread storm slab development.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Likely
Expected Size: 1 - 2
Persistent Slabs
30 to 60 cm of settled snow rests above a widespread layer of surface hoar that produced numerous avalanches last week. These slabs have been most sensitive to triggering at treeline.
Aspects: All aspects.
Elevations: Treeline, Below Treeline.
Likelihood: Possible - Likely
Expected Size: 1.5 - 2.5
Deep Persistent Slabs
Recent loading from new snow and wind has aggravated our region's deep persistent slab problem. Some very large and destructive avalanches have been sporadically failing on deeply buried weak layers, predominantly on north through east aspects in the alpine. Cornice falls are a likely trigger for these slabs.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Unlikely - Possible
Expected Size: 2.5 - 3.5