Avalanche Forecast South 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 southwest wind in the alpine, no significant snowfall expectedMONDAY: Scattered cloud cover, freezing level at valley bottom, around -20 C in the alpine, light variable wind at all elevations, no significant snowfall expected. A few centimeters 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 to strong southwest wind at ridgetop, a few centimeters of snow possible.
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.A persistent weak layer that was buried in mid-January continues to be reactive to human triggers. This layer is sensitive enough for avalanches to trigger remotely (from a distance). Activity on this interface continued into Friday as skiers triggered avalanches to size 1.5 on north through northeast facing terrain between 1650 and 1900 m. Small wind slabs were also reported from north and northeast facing terrain between 2200 and 2300 m.Human triggered avalanches size 1.5 to 2.5 were widespread last week on a variety of aspects at treeline and below.
20-70 cm of recent new snow sits on wind slab, surface hoar (feathery crystals), facets (sugary snow) and a crust on sun-exposed slopes. In many areas, recent winds have formed 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 40-90cm. 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 produce avalanches.
Likely - Possible
1 - 2
20-70 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.
If triggered, wind slabs may step down to deeper layers and result in even larger avalanches.Avoid freshly wind loaded features.Wind from a variety of directions has formed wind slabs in unusual locations at and above treeline.
Aspects: All aspects.
Elevations: Alpine, Treeline.
1.5 - 2.5
40-90 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.`
Any steep opening in the trees should be treated as suspect.Use conservative route selection, choose moderate angled and supported terrain with low consequence.Avoid convexities as well as steep, open and/or sparsely treed slopes at and below treeline.
Aspects: All aspects.
Elevations: Treeline, Below Treeline.