When the March sun shines warm and bright, avalanches may come rumbling into sight!
As the sun moves higher in the sky at this time of year, it has more power and can quickly destabilize slopes.
Coupled with a persistent weak layer problem in the upper snowpack, now is a good time to be making conservative terrain choices.
Last week's new snow overlays a buried persistent weak layer (PWL) that consists of suncrust, facets and/or surface hoar in some locations. Warm temps promoted the settling of a cohesive slab on top of this layer. Expect this slab to become more reactive during times of intense solar input.
Numerous wet loose and slab avalanches occurred in the past 4 days with daytime warming and solar input. These avalanches were up to size 3.0 and often gouged to ground at lower elevations where the snowpack had become isothermal.
Though the natural avalanche cycle is slowing today, human triggering remains possible.
Neighbouring operations have been seeing very large skier remote triggered avalanches on the facet interfaces down 30-80cm.
In the past 4 days, the top 5-10cm of the snowpack has undergone a melt-freeze cycle on all aspects below treeline, and on solar aspects into the alpine. The 40cm of storm snow that fell last week sits on a very faceted (sugary) upper snowpack.
A persistent weak layer (PWL) of surface hoar, facets and/or suncrust (Jan 30th) is 50-80cm down. Feb 16 is another PWL (facets/crust/surface hoar) down 30-40cms. Both of these layers are reactive to human triggering.
A brief blip of snow and wind on Wed, but otherwise benign conditions ahead.
Tonight Mainly cloudy. Alpine low -7°C. Light ridge winds. Freezing level (FZL) valley bottom
Tues Mix of sun/ cloud, isolated flurries. Alp high -6°C. Ridge wind SW 10-30km/h. FZL 1600m
Wed Mainly cloudy, flurries. 5cm. Alp high -6°C. Light W wind. FZL 1400m
Thurs Mix of sun and cloud. Alp high -5°C. Light W wind. FZL 1600m
