South Columbia

More snow and wind Saturday night will continue to build storm slabs at all elevations. Areas in the region that receive more than 20 cm overnight can expect "High" avalanche danger on Sunday.

Moderate - Timing, track, or intensity of incoming weather system is uncertain

TONIGHT: Mostly cloudy, flurries. Accumulation 10-20 cm. Ridge wind strong to extreme, southwest. Alpine temperature near -5. Freezing level 1300 m.SUNDAY: Cloudy, light flurries. Accumulation 2-4 cm. Ridge wind light to moderate, southwest. Alpine temperature near -3. Freezing level 2000 m.MONDAY: Mostly cloudy, flurries. Accumulation 2-8 cm. Ridge wind light to moderate, southeast. Alpine temperature near -3. Freezing level 2000 m.TUESDAY: Cloudy, flurries. Accumulation 10-20 cm. Ridge wind light to moderate, northwest. Alpine temperature near -5. Freezing level 1500 m.

Friday there were reports of several natural and skier-triggered storm snow releases (size 1) in steep and leeward alpine terrain.  As well as several natural storm slab releases up to size 2 on alpine, northeast through southeast aspects.Thursday pockets of reactive wind slab up to size 1 in alpine lees were reported, as well as skier-triggered, loose, wet avalanches to size 1.5 up to 2100m on solar aspects and below 1900m on north aspects. There were also reports from neighboring Glacier National Park on Thursday of a loose wet size 2 on a south aspect at 2100 m, and a size 4 slab that is thought to have been cornice triggered on a north aspect at 2800 m.Tuesday there was a report of a natural size 2 wind slab avalanche that was observed on a north facing feature at 2800 m.On Monday natural loose wet avalanches to size 2 were reported on all aspects with the exception of north between 1500 and 2500 m. A skier triggered size 1.5 storm slab was reported from a west/northwest facing feature between 1800 and 2200, failing on a crust. And riders near Blue Lake also triggered a size 2 slab avalanche on a north aspect at 2000 m. Read MIN report here.

About 10-20 cm of new snow overlies a crust on all aspects to at least 2300 m (and possibly higher on south-facing slopes), while 30-45 cm of storm snow can be found at higher elevations. There are now a few different crusts in the upper 50 cm of the snowpack, with only the most recently crust posing a concern for the recent storm snow.There is some lingering concern around the mid-March Persistent Weak Layer (PWL) in the alpine where it is found 70 to 120 cm below the surface. This buried crust/surface hoar interface was widely reactive but has not produced any avalanche activity in the past week. It is likely trending towards dormancy, but we need to keep it in the back of our minds as it is capable of producing large avalanches should it be triggered (think larger triggers such as; sleds, step-down from a surface avalanche or, a cornice collapse).Deeper persistent weak layers from December and January are considered dormant at this time.