Forecasted inversion may increase sensitivity of avalanche problems at tree line and in the alpine on Saturday.
Previous N winds have caused reverse loading and wind slabs down into the tree line; present SW winds continue to add to this problem. Main concern is where wind slab has built over weak faceted snow. Watch for hollow sounding snowpack.
December's persistent weaknesses sit over different layers depending on elevation and aspect. Below 1950m, a faceting rain crust is roughly 40-60cm down. Above 1950m, a buried surface facet layer down 20-30cm is the primary concern.
Relatively warm high pressure establishing through the weekend.
Saturday: Mix of sun and cloud. Freezing level to 1500m. Alpine high -5 C. Winds west light.
Sunday: Mix of sun and cloud. Freezing level to 1600m. Alpine high -4 C, low -8 C. Winds west light.
Monday: Isolated flurries. Freezing level valley bottom. Alpine high -6 C, low -10 C.
Previous N and present SW winds adding to wind slabs ALP and open TL. The mid-pack is highly faceted with active persistent weak layers from Dec. Interfaces within the facets found down ~30cm and ~60cm. These layers have varied sensitivity but if triggered can build large, destructive avalanches. Cornices are building.
Several large avalanches were observed on Tuesday around the Churchill Range to sz 2.5 in the alpine - some running to ground. Patrol south on Thursday noted no new activity in the poor lighting but significant wind effect and drifting evident at all elevations. Uncertainty exists re sensitivity of our slab problem in the alpine and at tree line.
