Avalanche Forecast
Issued: Jan 8th, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Persistent Slabs.
ldreier,
Avalanche Canada
Storm slabs might remain sensitive to human triggering and could step down to deeper weak layers in parts of the region. There is uncertainty how fast the snowpack will gain strength after the recent snow storm.
Summary
Confidence
Moderate - Uncertainty is due to how quickly the snowpack will recover and gain strength.
Weather Forecast
WEDNESDAY NIGHT: Cloudy with clear periods and isolated flurries, light northwest wind, alpine temperature -15 C, freezing level below valley bottom.
THURSDAY: Cloudy with sunny periods, moderate northwest wind, alpine temperature -11 C, freezing level at valley bottom.
FRIDAY: Cloudy with snowfall, accumulation 10 to 15 cm, moderate to strong southwest wind, alpine temperature -7 C, freezing level around 600 m.
SATURDAY: Cloudy with flurries, up to 5 cm accumulation, light westerly wind, alpine temperature -15 C, freezing level around 700 m.
Avalanche Summary
On Tuesday, several natural and skier triggered slab avalanches of size 1 were observed. One wet loose avalanche of size 2.5 was reported. It is possible that a natural avalanche cycle occurred on Monday during the peak of the storm.Â
Snowpack Summary
Around 30 to 40 cm of snow accumulated in the north of the region and 40 to 60 cm in the south of the region in the last few days. Below around 1500 m, most of this fell as rain. The snow fell with strong southwest wind, likely forming the deepest and most sensitive slabs in lee terrain features.Â
Deeper in the snowpack:
- The snow loaded a touchy weak layer of feathery surface hoar in sheltered areas above 1800 m. Areas such as Manning, Henning, Stoyoma, Duffey, and Hurley should be treated as suspect.
- A persistent weak layer is present near the bottom of the snowpack in the northern half of the region (e.g., Duffey, Hurley). The weak layer of sugary faceted grains exists around a hard melt-freeze crust from mid-November. This is an indicative snowpack setup for large and destructive avalanches. The likelihood of human-triggered avalanches decreases as the layer gets deeper but the consequence of triggering it would be severe.
- There are currently no concerns deeper in the snowpack near Coquihalla summit.
Terrain and Travel
- If triggered, storm slabs in-motion may step down to deeper layers and result in very large avalanches.
- Don't let the desire for deep powder pull you into high consequence terrain.
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
Problems
Storm Slabs
Around 30 to 40 cm of snow fell in the north of the region and 40 to 60 cm in the south of the region. The snow has formed storm slabs sensitive to human triggering, particularly in exposed terrain features, as the snow fell with strong southwest wind. These slabs may remain sensitive to human traffic on Thursday. Assess the bond of the recent snow before committing to avalanche terrain and travel conservatively.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
Two layers that cause concern:
- In many parts of the region, with the exception potentially being near Coquihalla summit, recent storm snow may overly a touchy surface hoar layer found around treeline elevations in sheltered areas. This layer has produced large avalanches that have propagated far.
- In the north half of the region, a weak layer is buried near the bottom of the snowpack. This layer has been responsible for recent large, destructive avalanches.
The likelihood of humans triggering these layers remains elevated due to the recent load applied to them. Storm slab avalanches could step down to these layers.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Jan 9th, 2020 5:00PM
