The weather and snowpack conditions are changing, and so should our mindset! The new snow will struggle to bond to old weak surfaces, expect sluffing in steep unsupported terrain. Fresh storm slab activity and the avalanche hazard will increase over the next few days.
30-60cm of settled snow buries the Dec 23 facet interface. This layer will be a concern in thin rocky areas, on convex rolls, or in areas where the snowpack is unsupported.
Storm slabs will build Thursday through Saturday as continued new snow buries weak low-density surface snow and the Jan 3rd Surface Hoar. Expect the Hazard to rise on Friday and Saturday as more snow falls, the wind blows and temperatures increase.
The Nov 17 layer, down 60-120cm, consists of facets, a rotting crust in some locations, and decomposing surface hoar. Though becoming less likely to trigger, the resulting avalanche would be quite destructive.
Explosive stability tests today produced six size 1-2 avalanches. They were very soft slabs failing on the Jan 3rd Surface Hoar which is buried ~15cm. 1 explosive-triggered avalanche stepped down to the Nov 17th PWL, 1m deep, and was a size 3
A dozen avalanches were recorded in the Highway Corridor on Jan 10th and 11th. Most of them were from extreme terrain on Mt Mcdonald and Mt Tupper.
No new avalanches were reported from the Back Country in Glacier National Park on January 10th or 11th; However, There were several avalanches reported on the 8th and 9th in the immediate vicinity of Rogers Pass. The nature of avalanches was wind slabs to persistent slab avalanches, with many large enough to injure or kill a person.
Storm slabs will be built throughout Thursday, Friday, and Saturday as continued new snow buries a weak layer of low-density snow and the Jan 3rd Surface Hoar.
The December 23rd facet interface is down ~60cm and appears to be gaining strength, but remains a concern in shallow snowpack areas.
The November 17th facet/crust/surface hoar layer is down ~100cm and has become less reactive in snowpack tests. When it does fail, there is a dramatic 'drop' of the entire snow column. Spooky!
Finally, some snow is in the forecast! On Thursday we should see, 10-15cm of new snow, the freezing level rising to ~1500m, and moderate to strong winds from the SW. Friday's forecast is very similar with another 15cm with similar winds and freezing levels. Only 5cm on Saturday, then it should dry up on Sunday as the storm passes by Rogers Pass.
