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 will occur on Monday 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
High - Confidence is due to a stable weather pattern; little change is expected for several days.
Weather Forecast
SUNDAY NIGHT: Clear skies, light northeast wind, alpine temperature -4 C.
MONDAY: Clear skies, light northeast wind, alpine temperature 1 C, freezing level 2400 m.
TUESDAY: Mix of sun and cloud, light to moderate northeast wind, alpine temperature -1 C and strong valley-bottom diurnal temperature changes, freezing level 1900 m.
WEDNESDAY: Clear skies, light northeast wind, alpine temperature -1 C and strong valley-bottom diurnal temperature changes, freezing level 1900 m.
Avalanche Summary
No new avalanches were observed on Sunday. A few small (size 1) wind slab avalanches were triggered naturally and by riders on Saturday. They were in alpine terrain and close to ridges.
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
An intense warming trend will raise the freezing level to around 2400 m.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, 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.
Weak faceted snow and melt-freeze crusts exist near the base of the snowpack in some of the region, particularly the eastern and northern parts. This layer is considered dormant, as it hasn't produced an avalanche since February 20th. The likelihood of triggering this layer may increase during this warming trend. There is also the potential for cornices to fail from warming, which could act as a trigger.
Terrain and Travel
- Extra caution for areas experiencing rapidly warming temperatures for the first time.
- The likelihood of deep persistent slab avalanches will increase with each day of warm weather.
- 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.
- Approach steep open slopes at and below treeline cautiously, buried surface hoar may exist.
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 2400 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
There is uncertainty on whether the weak faceted grains and melt-freeze crusts near the base of the snowpack are still a problem or not. This may vary for mountain to mountain. Should this basal weak layer exist where you travel and be triggered, the consequence of it would be devastating. The most likely spot for a human to trigger it would be in thin rocky terrain. A cornice fall also has the potential of triggering it. The likelihood of avalanche activity on this layer may increase during this warming period.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Mar 16th, 2020 5:00PM
