Avalanche Forecast
Issued: Jan 11th, 2023 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs, Persistent Slabs and Deep Persistent Slabs.
RC,
Avalanche Canada
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.
Summary
Confidence
Moderate
Avalanche Summary
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.
Snowpack Summary
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!
Weather Summary
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.
Terrain and Travel Advice
- Be carefull around freshly wind loaded features.
- If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
- Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.
Problems
Storm Slabs
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.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
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.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Deep Persistent Slabs
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.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Jan 12th, 2023 4:00PM
