Avalanche Forecast
Issued: Dec 25th, 2022 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Loose Wet and Wind Slabs.
rbuhler,
Avalanche Canada
Observations are very limited and there is a lot of uncertainty about how the ongoing storm and rainfall are affecting the snowpack, so a cautious approach is advised. It is recommended to avoid steep rain-soaked areas at lower elevations and watch for new wind slab formation at the highest elevations as temperatures drop on Monday.
Summary
Confidence
Avalanche Summary
On Saturday, limited observations during the storm included numerous natural loose wet avalanches up to size 1.5 and several natural slab avalanches up to size 2. These slabs were up to 40 cm thick and were typically releasing at around treeline elevation. Some of these slabs were triggered by loose wet avalanches in motion.
On Friday prior to the rain event, ski cutting triggered several size 1 wind slabs which were 20-30 cm deep.
Snowpack Summary
Rain is now expected to have soaked the surface at all elevations. As freezing levels drop on Monday, a new surface crust is expected to form. Depending on the timing of the cooling trend and the precipitation, new snowfall may accumulate over the rain-soaked surface and/or crust.
Before the rain, new storm snow buried a highly variable old surface which included an unsupportive sun crust on southern aspects, spotty surface hoar in sheltered terrain, and heavily wind-affected surfaces in wind-exposed terrain.
A layer of decomposing surface hoar crystals could be found down 70 cm prior to the storm. There is also a layer of weak, sugary facet crystals near the base of the snowpack. During recent testing, both of these layers were producing hard results and there have been no recent reports of avalanches occurring on these layers. However, the current storm loading will test these layers and there still remains potential for avalanches in motion to step down to these older layers.
Overall, the snowpack continues to present as thin and averaged 130 cm deep at treeline prior to the storm.
Weather Summary
Another period of heavy precipitation is expected Sunday overnight and into Monday morning. This is expected to be mainly rainfall but may switch to snowfall at the highest elevations as freezing levels descend on Monday.
Sunday night
Precipitation up to around 40 mm except the immediate SW coast which could see substantially more, strong to extreme S-SW wind, freezing level around 2000-2500 m.
Monday
Precipitation 15-30 mm, mostly expected to fall as rain but potentially switching to snowfall, strong to extreme S-SW wind, freezing level falling from 2000 m to around 1300 m.
Monday night and Tuesday
Precipitation 15-30 mm, moderate to strong SE-S wind, freezing level around 1200 m overnight and rising to around 1700 m during the day.
Wednesday
A mix of sun and cloud, moderate W wind, freezing level around 1000 m.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Avoid the alpine during periods of heavy loading from new snow wind and/or rain.
- Keep in mind that wet avalanches can be destructive due to their high density.
- The more the snow feels like a slurpy, the more likely loose wet avalanches will become.
- A crust on the surface will help bind the snow together, but may make for tough travel conditions.
Problems
Loose Wet
Rain has likely soaked the snow surface at most elevations. Use extra caution on all steep slopes while it is raining or where the snow surface is wet.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Wind Slabs
If new snowfall accumulates during the day on Monday, new wind slab formation is possible at the highest elevations.
Aspects: North, North East, East, North West.
Elevations: Alpine.
Likelihood
Expected Size
Valid until: Dec 26th, 2022 4:00PM
