Avalanche Forecast
Issued: Mar 15th, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Loose Wet, Wind Slabs and Deep Persistent Slabs.
mconlan,
Avalanche Canada
A rapid rise in freezing level is forecast and there is uncertainty on how quickly it will warm the snowpack. It could trigger an avalanche cycle. Treat the hazard as HIGH and avoid avalanche terrain and overhead exposure if you observe natural avalanche activity.
Summary
Confidence
Weather Forecast
SUNDAY NIGHT: Clear skies, light northeast wind, alpine temperature -6 C.
MONDAY: Clear skies, light northeaast wind, alpine temperature 0 C, freezing level 2100 m.
TUESDAY: Mix of sun and cloud, light to moderate northeast wind, alpine temperature -4 C and strong valley-bottom diurnal temperature changes, freezing level 1500 m.
WEDNESDAY: Clear skies, light northwest wind, alpine temperature -4 C and strong valley-bottom diurnal temperature changes, freezing level 1600 m.
Avalanche Summary
Small (size 1) wind slab avalanches were triggered by riders on Saturday in alpine terrain.
Looking forward, loose wet avalanche activity and cornice falls could be triggered with the warming trend. The potential of triggering wind slab avalanches remains possible in steep, alpine terrain.
Snowpack Summary
A rapid warming trend will raise the freezing level to around 2100 m on Monday.The warm air, coupled with strong radiation from the sun with clear skies, may rapidly weaken the snowpack and cornices. Expect to find moist or wet snow during the day, particularly on sun-exposed slopes, which could freeze into a melt-freeze crust overnight.
In the alpine, hard wind slabs may be found on all aspects due to variable wind directions. Recent wind has blown from the northeast, forming wind slabs in south to southwest terrain features. In sheltered terrain, about 30 cm of snow may overly a melt-freeze crust and potentially small surface hoar crystals.
In the northern part of the region (i.e., Duffey/Hurley/Gold Bridge), a deep instability may linger at the base of the snowpack. It has not produced an avalanche since February 17th. If one were to trigger the layer, it would likely be in a thin, shallow, rocky spot. A cornice fall could also trigger it. The likelihood of triggering this layer may increase during this warming trend.
Terrain and Travel
- Extra caution for areas experiencing rapidly warming temperatures for the first time.
- Back off slopes as the surface becomes moist or wet with rising temperatures.
- Minimize overhead exposure; avalanches triggered by warming or cornice fall may be large and destructive.
- Carefully evaluate steep lines for wind slabs.
- The likelihood of deep persistent slab avalanches will increase with each day of warm weather.
Problems
Loose Wet
The snowpack will undergo a rapid change as the freezing level rises and the sun shines on the mountains. The freezing level will reach around 2100 m for much of the region. The most snowpack warming will occur on sun-exposed aspects during the heat of the day. However, all aspects should be treated as suspect if you find moist or wet snow. Cornices will also weaken with the warming trend. Back off and avoid avalanche terrain if you start to notice natural avalanche activity.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Wind Slabs
Wind slabs may be found on all aspects in steep, alpine terrain. The wind has been blowing from the northeast, which is atypical. You may find wind slabs in terrain features that don't typically have them. These slabs could remain touchy, as they may overly a weak layer of surface hoar.
Aspects: All aspects.
Elevations: Alpine.
Likelihood
Expected Size
Deep Persistent Slabs
In the north of the region (e.g. Duffey, Hurley, Goldbridge), a deep persistent weak layer of faceted grains near the ground presents a lingering concern on steep, shallow slopes in the alpine. The likelihood of triggering this layer may increase over the coming days as the snowpack warms from warm air temperature and sunny skies.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Mar 16th, 2020 5:00PM
