Avalanche Forecast
Issued: Dec 25th, 2019 2:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs.
ghelgeson,
Avalanche Canada
Natural avalanche activity has waned, but a persistent slab 100 to 160 cm in depth remains very much in play. You can't feel a problem like this under your track or skis, the only way to manage this is to stick to relatively simple terrain free of overhead hazard.
Summary
Confidence
Weather Forecast
The most recent weather model runs are showing very little precipitation through the end of the year aside from small dribs and drabs. Looks like the wind will begin to pick up out of the south/southwest on Thursday, especially in the higher alpine terrain features.
WEDNESDAY NIGHT: Freezing level at valley bottom, light northwest wind, no significant precipitation expected.
BOXING DAY: Clear skies at dawn with increasing cloud cover throughout the day, overcast by sundown. Freezing level at valley bottom, calm/light wind up to at least 2000 m with potential for moderate to strong south/southwest wind in the high alpine late in the day, trace of snow possible during the day, potential for 4 to 10 cm by Friday morning.
FRIDAY: Broken cloud cover, freezing level at valley bottom, calm/light wind at most elevations, moderate to strong west/northwest wind in the alpine, trace of snow possible during the day.
SATURDAY: Scattered cloud cover at dawn building to broken by sundown, freezing level at valley bottom, calm/light wind at most elevations, potential for moderate to strong southerly wind in the alpine, no precipitation expected.
Avalanche Summary
The recent storm was a significant one and there is now a great deal of uncertainty as to how quickly the snowpack is regaining strength. Avalanche activity is tapering, but avalanches during and just after the storm were spectacularly large and destructive.
On Tuesday some natural avalanches up to size 2 were observed in ridge top start zones on a northwest facing slope around 2100 m. There were also some rather spooky size 2 storm slabs on east/southeast facing slopes down in the trees at 1900 m.
On Monday natural avalanche activity from size 2 to 3 was observed on a variety of aspects above 2100 m. Control work produced avalanches from size 2 to 4 that involved all elevation bands, some mature timber was taken out by very large avalanches.
On Friday, Saturday & Sunday there were numerous reports of natural, human and explosive triggered avalanches up to size 4. A number of these were triggered remotely.
Snowpack Summary
The North Columbias received upwards of 80 cm from last weekend's big storm which is slowly settling into a slab. There is now anywhere from 100 to 160 cm of snow resting on a widespread layer of large, feathery, surface hoar which we're calling the "December 11th Surface Hoar." Activity on this interface has begun to taper, but this layer produced some very large natural avalanches during and just after the storm.
A combination of surface hoar, crust & facets formed in late November is now over 170 cm deep. This layer is likely trending toward dormancy.
Terrain and Travel
- Use conservative route selection and resist venturing out into complex terrain.
- Choose slopes that are well supported and have limited consequence.
- Caution around convexities or sharp changes in terrain.
- Avalanche hazard may have improved, but be mindful that deep instabilities are still present.
Problems
Persistent Slabs
All of the old storm snow is slowly settling into a slab which rests on weak surface hoar 100 to 160 cm below the surface. Natural avalanche activity has waned, but human triggering remains possible, especially in more challenging/complex terrain. This isn't the kind of avalanche problem you can feel under your skis, track or feet, it's far too deep for that. The only way to manage a problem like this is to choose well supported terrain free of overhead hazard.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Dec 26th, 2019 5:00PM
