South Columbia

Expect new snow and strong winds to form storm slabs and grow cornices. Sloughing, and cracking around skis and sleds are signs that the new snow is bonding poorly to the old surface. Avoid wind loaded areas with pillowy or chalky looking snow.

Moderate - Forecast snowfall amounts are uncertain

TONIGHT: Flurries. Accumulation 5-10 cm. Ridge wind strong to extreme, southwest. Temperature -15. Freezing level valley bottom.SUNDAY: Snow. Accumulation 5-10 cm. Ridge wind moderate to strong, southwest. Temperature -7. Freezing level 500 m.MONDAY: Mostly cloudy, light flurries. Accumulation trace. Ridge wind light to moderate, southwest. Temperature -5. Freezing level 700 m.TUESDAY: Cloudy, flurries. Accumulation 5-10 cm. Ridge wind light to moderate, southwest. Temperature -5. Freezing level 900 m.

Thursday we received reports of large (size 2.5) natural and cornice triggered avalanches on north and east aspects above 2200 m. At least one of these avalanches failed on deep weak layer, with a crown depth of 200 cm. There was also a report of skier's remotely (from a distance) triggering a size 2.5 slab avalanche on a south aspect at 2300 m that is believed to have failed on the crust that was buried mid-February.Throughout the week from Tuesday through Friday, there have been numerous reports of skier triggered slab avalanches (size 1-1.5) on predominantly steep, northeast through south-facing features between 1900 -2500 m, that also failed on the mid-February crust..On Monday, several natural wind slab avalanches to size 3 were reported on a wide range of aspects above 2100m. 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.

About 5-10 cm of new snow now covers the old snow interface which consists of sugary facets, as well as sun crusts on solar aspects and surface hoar on shaded, wind-protected slopes. Below this interface lies another interface, with similar character and distribution that was buried mid-February and is now 40-60 cm below the surface. This layer has been reactive in recent snowpack tests and several avalanches have been reported to have failed on this layer in the past week.Within the mid and lower snowpack are several persistent weak layers that are beginning to show signs of improving but still remain suspect. Two surface hoar/ crust layers buried in January are now 150-200 cm below the snow surface. At least one of these layers can be found on all aspects and elevations.Deeper in the snowpack (200 - 250 cm deep) is a facet/crust/surface hoar layer buried in December that is most prevalent at treeline elevations and below.Near the base of the snowpack is a crust/facet combo layer buried in late November.