South Columbia

Snow and wind beginning on Friday will add to existing slabs and grow cornices at upper elevations. Sloughing and cracking around skis and sleds are signs that the new snow is bonding poorly to the old surface. More snow is expected for Sunday.

Moderate - Forecast snowfall amounts are uncertain

FRIDAY: Flurries. Accumulation 5-10 cm. Ridge wind light, southwest. Temperature -12. Freezing level valley bottom.SATURDAY: Mix of sun and cloud, light flurries. Accumulation trace. Ridge wind light, west. Temperature -8. Freezing level valley bottom.SUNDAY: Snow. Accumulation 10-20 cm. Ridge wind moderate to strong, southwest. Temperature -7. Freezing level 700 m.

On Wednesday there were multiple reports of skier triggered slab avalanches, size 1-1.5 on predominantly steep, east through south-facing features between 1900 -2500 m.Tuesday numerous skier triggered storm and wind slab avalanches up to size 1.5 were reported. Most of these failed on the mid-February interface which was especially reactive on solar aspects where a suncrust was buried.On Monday, several natural wind slab avalanches to size 3 were reported on a wide range of aspects above 2100m. On Sunday we received reports of several wind slab avalanches to size 2, on a wide range of aspects. See here for a good example in the MIN report. Although deeper, persistent avalanche activity has become less frequent over the past week, light triggers in shallow rocky areas, as well as large triggers such as a cornice collapse or step down from a wind slab release, still have the potential to result in large destructive avalanches.

40-60 cm of recent storm snow has settled into a slab in the upper snowpack. Strong winds, most recently from the north / east, redistributed these accumulations into tiff wind slabs in wind-exposed terrain. These accumulations overlie the old interface that was buried mid-February consisting of; a mix of older wind slabs in exposed higher elevation terrain, a sun crust on steep solar aspects, a rain crust below 1600m, and surface hoar on sheltered slopes.Below the snow surface several persistent weak layers make up a complex snowpack which is slowly beginning to show signs of improving but still remains suspect . In the top 150-200 cm of the snowpack, two surface hoar/ crust layers buried in January can be found. Expect to find one or the other of these on all aspects and elevations.Deeper in the snowpack (200-250 cm) is a facet/crust/surface hoar layer from December, most prevalent at and below tree line.Near the base of the snowpack is a crust/facet combo, most likely to be triggered from thin spots in the alpine.