Ongoing periods of strong wind continue to develop reactive wind slabs in exposed terrain and two buried weak layers remain a concern for persistent slab avalanches. Give the snowpack time to recover from the recent warming and continue to use a conservative mindset.
Recent strong winds from the SW through NW have formed reactive wind slabs in exposed terrain at higher elevations. Ongoing wind on Monday will continue to develop these wind slabs where there is still loose surface snow available for transport.
The weekend warming has weakened cornices which are expected to remain weak on Monday.
Two buried weak layers remain a concern. The late-January crust/surface hoar is down 20-40 cm and the mid-January crust/facets is down 50-70 cm. Both layers woke up with the weekend warming and produced avalanches.
Freezing levels may stay elevated overnight and Monday morning but there is still a lot of uncertainty regarding the intensity and extent of any lingering warming.
Sunday Night: Mainly clear, moderate SW wind, freezing levels 1500-2000 m with a temperature inversion.
Monday: Increasing cloud cover in the afternoon with a chance of flurries, moderate to strong SW wind, afternoon freezing levels around 1600 m.
Tuesday: Mainly sunny, light to moderate SW wind, freezing levels reaching around 1600 m.
Wednesday: Mainly sunny, light to moderate W wind, freezing levels climbing to around 2000 m.
An early report from Sunday includes an explosive-triggered size 2.5 wind slab which failed on the mid-January crust and stepped down to a deeper layer in the snowpack.
On Saturday, a natural cornice fall triggered a size 2 storm slab which failed down 30 cm and then stepped down to deeper layers in the snowpack. Several natural wind slabs size 1.5-2.5 were also reported in alpine terrain on NW-NE aspects. A small cornice failure was also reported which did not trigger a slab.
20-40 cm of rapidly settling snow now typically overlies the January 30 interface which consists of a melt-freeze crust at lower elevations and on solar aspects extending into the alpine, surface hoar in wind-sheltered areas at and below treeline, and small facets in some areas. With the recent warming, the surface snow has settled into a cohesive slab over the weak layer and a new surface crust will likely form as temperatures drop.
Periods of strong wind over the weekend, mainly from the southwest through northwest, have formed reactive wind slabs in exposed terrain at higher elevations. Ongoing wind on Monday will likely continue to develop reactive wind slabs where there is still loose snow available for transport.
The widespread January 18 rain crust is now around 50-70 cm deep with weak faceted snow above. This layer appears to have woken up with the weekend warming and at least two avalanches likely involved this layer.
The early December crust/facet persistent weak layer is now 100-200 cm deep. This layer produced numerous large avalanches in January but is now considered dormant. See this forecaster blog on how to manage this layer as it may come into play again later this season.
