Danger ratings may have improved but avalanche conditions remain tricky and buried weak layers still triggerable.
Avoid terrain features where the snowpack varies from thick to thin, where weak layers can be more easily triggered. Check out the new Forecasters' Blog for more details on managing this season's challenging snowpack.
Wind slabs can be found in west through east facing terrain - loaded by the southerly winds. Wind slabs will be especially reactive where they sit over a layer of crust or surface hoar.
Avalanches triggered in wind-loaded terrain have the potential to step down to deeper weak layers, creating larger than expected avalanches.
A layer of surface hoar, facets and/or a crust sits 40 to 70 cm deep, which is a prime depth for human triggering. This layer has been most problematic around treeline and lower alpine elevations and has produced large avalanches.
Keep terrain selection conservative in these elevation bands and practice good travel habits to reduce your exposure.
A layer of large and weak facets sits near the base of the snowpack. This layer has most recently been problematic in lower alpine elevations.
Avoid thin and rocky start zones where weak layers sit closer to the surface, riders are most likely to trigger an avalanche on this layer in terrain with shallow or variable snow depths.
Although persistent/deep persistent slab avalanche activity has tapered off in recent days, reports continue to trickle in. Natural and human-triggered size 2s reported as recently as Saturday show evidence that these layers are still reactive to human triggers and are capable of producing large avalanches.
Between the 1st and 5th of January, widespread avalanche activity was reported on persistent/deep persistent weak layers throughout the Columbias and Western Purcells. These avalanches were naturally and human triggered, up to size 3 (very large) and failed on the weak layers described in the Snowpack Summary from 70-200 cm deep. Avalanches occurred on all aspects, and mostly between 1800 and 2500 m in elevation. Check out these MIN reports from Joss Mountain, & North McCrea Mountain for an idea of the scale and features of concern.
Small slabs in wind loaded features have also been triggered by riders, which have the potential of stepping down to these deeper weak layers.
5-10 cm of new snow falls over a well-settled upper snowpack. A small layer of surface hoar and/or a sun crust may exist near the surface. Consistent southerly winds are redistributing surface snow into wind loaded features at upper elevations. New wind slabs may sit over the layer of surface hoar and/or crust.
Buried weak layers in the mid to lower snowpack continue to be a concern although avalanche activity appears to be tapering off:
A layer of crust, facets and/or surface hoar buried around Christmas sits 40-70 cm deep.
A layer of large and weak facets from mid November sits near the ground.
This year's snowpack is weaker than usual, as described in our Forecasters' blog.
Sunday night
5-10 cm new snow. Moderate southerly wind easing by morning. Alpine low of -6 °C. Freezing level 500 m.
Monday
Mix of sun and cloud with isolated flurries. Light to moderate southerly wind. Alpine high of -3 °C. Freezing level 500-800 m.
Tuesday
Cloudy with sunny breaks in the afternoon. Light southerly winds. Alpine highs of -4 °C. Freezing level 500-800 m.
Wednesday
A mix of sun and cloud. Light to moderate southerly winds. Alpine high of -5 °C. Freezing level 500 m.
More details can be found in the Mountain Weather Forecast.
