Avalanche Forecast
Northwest Coastal
New snow, wind and mild alpine temperatures are increasing danger ratings. Now is the time for very conservative terrain choices and avoiding exposure to overhead avalanche hazard. The potential for large avalanches to run long distances exists.
Avalanche Problem 1: Storm Slabs
What Elevation?
Which Slopes?
Chances of Avalanches?
Expected Size?
Travel and Terrain Advice
- Use conservative route selection, choose moderate angled and supported terrain with low consequence.
- Watch for whumpfing, hollow sounds, shooting cracks or recent avalanches.
- Be careful with wind loaded areas, especially near ridge crests and roll-overs.
Avalanche Problem 2: Persistent Slabs
What Elevation?
Which Slopes?
Chances of Avalanches?
Expected Size?
A weak layer exists 120-150 cm below the surface. It may still be possible for humans to trigger persistent slab avalanches on this layer, or for a storm slab release to step down to this layer resulting in a very large avalanche.
Travel and Terrain Advice
- Avoid lingering in runout zones. Large avalanches may run long distances.
- Minimize overhead exposure during periods of heavy loading from new snow, wind.
- Caution around convexities or areas with a thin or variable snowpack.
Avalanche Summary
Tuesday there were reports of two skier triggered size 1 wind slab releases just northwest of Terrace, where a soft slab up to 35 cm deep had formed on wind-loaded features.
Monday evidence of a natural avalanche cycle from size 2.5 - 3.5 was reported on north to south aspects between 1000-1700 m, west of Terrace, with several persistent slabs suspected to have failed on the mid or early January layers during the height of the weekend's storm.
Sunday north of Meziadin Junction a natural size 4 and a natural size 3.5 were observed on a southwest and northeast aspect at 1800-2000 m and are suspected to have failed on the mid-January layer.
On Saturday wind and storm slab avalanches failed naturally to size 2 on a variety of aspects in both alpine and treeline elevation bands. A natural size 3 persistent slab avalanche was observed on a steep north facing alpine feature with a crown up to 100 cm in depth, which suggests the mid-January interface was involved. A another very large avalanche (size 3.5) was reported from an unknown aspect/elevation.
Snowpack Summary
Wednesday's storm delivered another 20-30 cm of new snow during the day, and a mix of rain and freezing rain for areas west of Terrace, bringing storm snow totals of over 100 cm in the last 10 or 12 days.
Beneath the storm snow lies a 5-20 cm thick crust that was buried early February and can be found 40-90 cm below the surface on all aspects up to 1400 m.
A weak layer buried in mid-January is 120-150 cm below the surface and remains a concern. In most areas this layer is a crust, but it may also be surface hoar in sheltered areas at treeline and below. This layer produced a few human triggered avalanches throughout the region over the past week, and may remain reactive as it adjusts to the weight of the new snow.
In thinner snowpack areas (north and inland), deeper crust / surface hoar layers that were buried in December and early January may still be a concern. They are buried over 150 cm below the surface, but may be triggerable from shallow spots.
Weather Forecast
TONIGHT: Snow. Accumulation 10-15 cm. Ridge wind light, north. Temperature -5. Freezing level 300 m.
THURSDAY: Mix of sun and cloud, light flurries. Accumulation up to 2 cm. Ridge wind light, northeast. Temperature -6. Freezing level valley bottom.
FRIDAY: Mostly sunny. Ridge wind light, northeast. Temperature -8. Freezing level valley bottom.
SATURDAY: Mostly cloudy. Ridge wind light, south. Temperature -5. Freezing level valley bottom.
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Wednesday's storm event has formed reactive storm slabs at all elevations but especially at upper elevations and wind-exposed areas. Be aware that these slabs overlie a crust from early-February and may also step down to a deeper weak layer.