Avalanche Forecast North Columbia
Saturday 9th February 2019
Strong to extreme wind has formed reactive wind slabs in the last 24 hours in unusual locations and it's NOT better below treeline where a touchy persistent slab is capable of producing large human triggered avalanches. Forecaster blog here.
Moderate - Wind effect is extremely variable
Cold, dry, arctic air continues to dominate the weather pattern for the foreseeable future.SATURDAY NIGHT: Freezing level at valley bottom, around -20 C in the alpine, light variable winds at all elevations, no significant snowfall expected.SUNDAY: Clear skies at dawn with cloud cover increasing throughout the day, freezing level at valley bottom, around -20 C in the alpine, light variable wind at valley bottom, light south/southwest wind in the alpine, no significant snowfall expectedMONDAY: Scattered cloud cover, freezing level at valley bottom, around -20 C in the alpine, light southerly wind at all elevations, no significant snowfall expected. A trace of snow possible Monday night.TUESDAY: Broken cloud cover, freezing level at valley bottom, around -20 C in the alpine, light variable wind at most elevations with moderate southwest wind at ridgetop, a trace of snow possible.
On Friday a natural size 2 wind slab avalanche was observed on an east facing aspect near 3000 m. Strong to extreme wind Friday night into Saturday may have initiated a natural wind slab avalanche cycle. Check out this MCR report of a skier triggered wind slab from an east facing aspect at 2370 m in the adjacent Glacier National Park region on Saturday.The North Columbias are the hotspot for human triggered persistent slab avalanches as a weak layer that was buried in mid January continues to be sensitive to human triggers. This layer is touchy enough for avalanches to be triggered remotely (from a distance). SKIER AND SNOWMOBILE TRIGGERED AVALANCHES SIZE 1.5 TO 2.5 HAVE BEEN REPORTED ON ALL ASPECTS AT AND BELOW TREELINE ALMOST EVERYDAY FOR THE LAST TWO WEEKS. The bulk of this activity is occurring below 1900 m. This MIN report from Monday does a great job of illustrating the sensitivity of this weak layer.
30-80 cm of recent new snow sits on surface hoar (feathery crystals), facets (sugary snow), wind slabs and a crust on sun-exposed slopes. In many areas, recent winds have redistributed the new snow, forming wind slabs on all aspects due to shifting wind directions.The most notable feature in the snowpack at this time is a persistent weak layer that was buried in mid January, which is now buried 50-100 cm. This layer consists primarily of surface hoar, however there is also a crust associated with it on sun-exposed slopes. This layer is the most prominent at treeline and below, and continues to be produce avalanches.
Likely - Possible
1 - 2
30-80 cm of old storm snow continues to be redistributed by arctic wind out of the north and east. Wind slabs forming at treeline have the potential to step down to the buried surface hoar resulting in large avalanches.
Wind from a variety of directions has formed wind slabs in unusual locations at and above treeline.If triggered, wind slabs may step down to deeper layers and result in even larger avalanches.Avoid freshly wind loaded features.
Aspects: All aspects.
Elevations: Alpine, Treeline.
1.5 - 2.5
50-100 cm of snow sits above a weak layer of surface hoar (feathery crystals) and crust. This layer continues to be reactive to human triggers. The trees are not a safe haven right now, in fact treeline may be the most dangerous elevation on Sunday.`
Avoid convexities as well as steep, open and/or sparsely treed slopes at and below treeline.Use conservative route selection, choose moderate angled and supported terrain with low consequence.Any steep opening in the trees should be treated as suspect.
Aspects: All aspects.
Elevations: Treeline, Below Treeline.