Avalanche Forecast
Issued: Jan 19th, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs, Deep Persistent Slabs and Loose Wet.
cgarritty,
Avalanche Canada
Make observations of surface conditions to determine whether you need to manage loose wet or wind slab avalanche hazards on Monday, but be mindful of conditions that vary with elevation, especially in the north of the region.
Summary
Confidence
Moderate - Recent weather patterns have resulted in a high degree of snowpack variability within the region.
Weather Forecast
Sunday night: Cloudy with easing flurries bringing a trace to 10 cm of new snow to alpine and upper treeline. Light rain below 1700 metres in the north of the region and to mountaintop in the south. Moderate to strong south winds. Freezing levels peaking at 2000-2400 metres, warmest in the south of the region.
Monday: Mainly cloudy with scattered flurries at a trace to 10 cm of new snow in the north of the region. Clear periods in the south. Moderate southwest winds easing over the day. Alpine high temperatures around -3 in the north of the region, closer to 0 in the south.
Tuesday: Mainly cloudy with flurries and a trace to 5 cm of new snow. Light to moderate south winds. Alpine high temperatures around -5.
Wednesday: Mainly cloudy. Light south winds. Alpine high temperatures around -5.
Avalanche Summary
Reports from Saturday included observations of a recent natural avalanche cycle producing slab avalanches up to size 2.5 (large) in the Duffey lake area. Around Hurley Pass, new snow accumulations began reacting as small (size 1) loose dry releases with skier traffic. Observations in most areas were limited by stormy weather.
A report from Thursday in the McGillivray Pass area in the north of the region included observations of several storm slabs reaching size 2.5 (large) releasing naturally from steep north aspects in the alpine during a period of intense snowfall.
Last Saturday, a few explosives-triggered avalanches in the north of the region stepped down to the Christmas surface hoar layer mentioned in our snowpack summary, buried 50-60 cm deep at the time.
Snowpack Summary
Relatively continuous light snowfalls over the past few days have brought recent storm totals to 25-50 cm in the north of the region. This recent snow has been heavily wind-affected in exposed areas at all elevations. The south of the region saw little from the weekend storm and is expected to see rain to mountaintop over Sunday night.
The new snow buried recent wind slabs and wind-affected surfaces in exposed areas at all elevations and soft, low density snow in sheltered areas. Similar surfaces are instead likely to form a new melt-freeze crust on Monday in the south of the region.
90-150 cm of snow currently sits above a weak layer of surface hoar from Christmas that professionals are tracking in the north of the region. It may be found at treeline and below on shaded aspects in sheltered areas.Â
A deep persistent weak layer remains a serious concern at the bottom of the snowpack in the northern half of the region (e.g., Duffey, Hurley). It's made up of sugary faceted grains and a hard melt-freeze crust. This layer is most likely to be triggered in thin, rocky features where it exists closer to triggering forces on the surface.
There are currently no concerns about deep weaknesses in the snowpack near Coquihalla summit and elsewhere in the south of the region.
Terrain and Travel
- Avoid freshly wind loaded terrain features.
- As surface loses cohesion due to melting, loose wet avalanches become common in steeper terrain.
- In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.
Problems
Wind Slabs
A week of continuous light snowfall and strong wind has left a variety of wind slabs at higher elevations in the north of the region. Some are old and stubborn, but newer, more reactive slabs may be found on north through east aspects in exposed areas in the alpine and upper treeline.
Aspects: North, North East, East, South East, West, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Deep Persistent Slabs
Two layers that cause concern in the northern part of the region include:
- A 90-150 cm-deep weak layer of surface hoar layer found around treeline elevations in sheltered areas. It may still be triggered by a person in steep, sheltered openings around treeline.
- A weak layer buried near the bottom of the snowpack which continues to produce sporadic very large avalanches. This layer is most likely to be triggered in steep, thin, rocky areas in the alpine or upper treeline.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Loose Wet
Wet loose avalanche conditions should ease as temperatures drop on Monday, but surface snow will remain unstable at elevations that continue to see rain accumulating instead of new snow. Be conscious of this problem around steep slopes at lower elevations.
Aspects: All aspects.
Elevations: Below Treeline.
Likelihood
Expected Size
Valid until: Jan 20th, 2020 5:00PM
