Avalanche Forecast
Issued: Mar 17th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs.
mconlan,
Avalanche Canada
A multi-day storm will start building new slabs in the region. Assess for slab formation over the day, particularly at higher elevations.
Summary
Confidence
Moderate - Uncertainty is due to the track & intensity of the incoming weather system.
Weather Forecast
WEDNESDAY NIGHT: Partly cloudy, 30 to 40 km/h south wind, alpine temperature -3 C, freezing level 1600 m.
THURSDAY: Cloudy with snowfall, accumulation 10 to 20 cm, 40 to 60 km/h south wind, alpine temperature -4 C, freezing level 1400 m.
FRIDAY: Cloudy with snowfall, accumulation 20 to 30 cm, 40 to 60 km/h southeast wind, alpine temperature -6 C.
SATURDAY: Cloudy with snowfall, accumulation 10 cm, 20 km/h southwest wind, alpine temperature -6 C.
Avalanche Summary
Cornices were triggered by explosives on Monday to Wednesday, releasing large chunks that could kill a person but they did not trigger slabs. Avalanche activity is expected to increase in the coming days as a multi-day storm impacts the region.
There's been some large avalanches in the past week around the Whistler area, including near Mt. Fee (see here and here) and last week on Mt. Fissile in the Whistler backcountry. These avalanches may be due to extensive wind loading, but they may also be associated with isolated weak snow from earlier this season.
Snowpack Summary
New wind slabs are expected to form over Thursday as a storm brings in snow and strong south wind. Suspect terrain will include lee (northerly) terrain features adjacent to ridges at treeline and alpine elevations. It is possible that sufficient snow will accumulate in sheltered terrain to form storm slabs, so use particular caution in steep terrain if you find around 10 cm or more of fresh snowfall. The new snow will overly a melt-freeze crust up to around 1600 m and higher on sun-exposed slopes or wind-affected dry snow on northerly aspects at high elevations. Remember that cornices along ridgelines are large at this time of year and always have the possibility of failing naturally or from the weight of a human.
Around 100 to 300 cm of consolidated snow may overly sugary faceted grains formed earlier this season. These layers are expected to be spotty around the region and we haven't received conclusive evidence of them being the culprit of avalanche activity. That being said, it is possible they may be associated with a few recent large avalanches around the Whistler area.
Terrain and Travel
- Watch for signs of slab formation throughout the day.
- Look for signs of instability: whumphing, hollow sounds, shooting cracks, and recent avalanches.
- Extra caution is needed around cornices under the current conditions.
Problems
Wind Slabs
New wind slabs are expected to form from fresh snow and strong southerly wind. Use caution in lee terrain features near ridgelines. Should you find around 10 cm or more accumulation in your riding area, storm slabs could also be triggered in steep, sheltered terrain.
Note that there's been reports of large avalanches triggered by riders and cornices in the past week, so use particular caution in committing terrain with high consequences.
Aspects: North, North East, East, West, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Mar 18th, 2021 4:00PM
