Avalanche Forecast

Moderate -

TONIGHT: Snow. Accumulation 20-30 cm. Ridge wind strong, southwest. Temperature -6. Freezing level valley bottom.THURSDAY: Snow. Accumulation 15-20 cm. Ridge wind light, east. Temperature -8. Freezing level valley bottom.FRIDAY: Mix of sun and cloud. Ridge wind light, northeast. Temperature -10. Freezing level valley bottom.SATURDAY: Sunny. Ridge wind light, west. Temperature -8. Freezing level valley bottom.

On Tuesday a snow cat remotely (from a distance) triggered a size 3-3.5 persistent slab avalanche that stepped down from 80-250 cm and ran to ground in the lower start zone on a south aspect at 2100 m. Explosive control work also produced cornice releases up to size 2.5, but failed to produce any slab results on the slopes below. Monday natural wind slab activity up to size 1.5 was reported on steep, north-east facing features. Ski cuts and explosive control work produced several storm slab results (size 1.5-2) on north-east through south-east aspects between 1400-1600 m where the late January crust is present.On Saturday the east facing Mt. Corrigan slidepath produced a very large, natural avalanche. The avalanche is estimated to be a size 4.0, and it took out mature timber in the path as it overran the Flathead FSR south of Corbin. Also on Saturday, several 20-50 cm thick storm slabs were triggered with explosives at treeline elevations. A few natural cornice falls occurred on north and east aspect, one triggering a size 2 storm slab on the slope below.

Recent storm snow covers two crusts that formed late January and early February and are now buried 20-40 cm below the surface at elevations below 1700 m in the Fernie area. At higher elevations and in exposed areas at treeline winds have formed reactive wind slabs.For the past month there has been regular avalanche activity on multiple weak layers in the mid and lower snowpack. A layer buried mid-January is composed of surface hoar on sheltered aspects (especially prominent from 1400-1900 m) and a sun crust on solar aspects and is 60-80 cm deep. Another surface hoar layer from early-January is 90-110 cm deep. A widespread weak layer from mid-December composed of facets, crusts, and surface hoar is 120-160 cm deep. Finally, a rain crust with sugary facets buried in late-November is near the base of the snowpack.The bottom line is the snowpack structure is weak. Human triggering is most likely on the shallower weak layers, however a release near the surface also has the potential to step down to deeper layers and become a much larger avalanche.