Avalanche Forecast
Regions:
Friday's storm built fresh soft slabs which contributed to the persistent slabs that were already overlying a weak base.
With many natural avalanches observed in the alpine Saturday, expect the avalanche hazard to remain elevated through Monday as another dose of wind and snow is on track to arrive Saturday evening.
Confidence
Moderate
Avalanche Summary
A forecasting team to the 93N today observed many new avalanches in alpine terrain. Several sz 1-1.5 persistent slabs around 40cm deep were seen below steep rock features that had apparently been triggered by the more widespread loose dry activity in the past 24 hrs. Elevated winds remained with continued loose dry events observed to be spilling out of extreme terrain such as gullies on Bow Peak. Both SSV and LLSA reported dealing with thin soft slabs and seeing a couple of sz 1-2 persistent slabs in closed or nearby backcountry terrain.
Snowpack Summary
10 to15cm of new snow arrived with strong to extreme SW-W winds over the past 36 hours. Freezing levels have returned to valley bottom but were higher in eastern areas through Friday : snow accumulations taper with elevation. Mild temperatures and wind have promoted new slab development. The snowpack below these slabs is a mix of facets, some spotty surface hoar, and sun crust on steep south aspects. There is even some classic Rockies depth hoar forming at the base in thinner areas. 40-80 cm of total snow exists at treeline throughout the region, with up to 120 cm in loaded alpine features.
Weather Summary
Another cold front will pass through the region Saturday overnight brining 5-10 cm of snow favoring western and northern areas. Winds will shift to the SW and increase to 60km/h.. Sunday a few flurries will remain as winds weaken to 40km/h and shift NW. A ridge will build through Sunday with winds shifting N and decreasing to 20km/h overnight.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Fresh snow rests on a problematic persistent slab, don't let good riding lure you into complacency.
- If triggered, loose dry avalanches may step down to deeper layers resulting in large avalanches.
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
Avalanche Problems
Persistent Slabs
Anywhere a slab exists over the weaker base has the potential for avalanches right now. Slabs overly weak facets (and even some depth hoar) in most areas, as well as suncrusts and surface hoar in isolated locations. With more snow and wind on the way, we expect this problem to build for Sunday.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Likely
Expected Size: 1.5 - 2.5
Loose Dry
While winds are elevated and there are new snow inputs, loose dry avalanches can be expected. This is mainly a problem for ice climbers and skiers in steep, gullied terrain but the potential for these events to trigger slabs should be kept on everyone's radar.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Likely
Expected Size: 1 - 1.5
Wind Slabs
5-15 new snow distributed by strong winds created thin soft slabs. Many of these sit on older wind pressed surfaces. Continued snow and SW winds will add to this problem overnight Saturday.
Aspects: North, North East, East, South East, South, North West.
Elevations: Alpine, Treeline.
Likelihood: Likely
Expected Size: 1 - 1.5