Avalanche Forecast
Issued: Mar 14th, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs, Loose Wet and Deep Persistent Slabs.
mconlan,
Avalanche Canada
Strong northeast wind has formed wind slabs on atypical aspects. A warming trend will start to destabilize the snowpack on sun-exposed slopes as well as cornices.
Summary
Confidence
Moderate - Uncertainty is due to how the snowpack will react to the forecast weather.
Weather Forecast
SATURDAY NIGHT: Clear skies, moderate northeast wind, alpine temperature -14 C.
SUNDAY: Clear skies, moderate to strong northeast wind, alpine temperature -7 C, freezing level rising to 1000 m.
MONDAY: Clear skies, light to moderate northeast wind, alpine temperature 1 C, freezing level 2300 m.
TUESDAY: Clear skies, light to moderate northeast wind, alpine temperature 0 C, freezing level 2000 m.
Avalanche Summary
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.
It will remain possible for humans to trigger wind slab avalanches. Loose wet avalanche activity and cornice falls could also be triggered with the warming trend.
Snowpack Summary
A major warming trend is forecast for the coming days, which could rapidly weaken the snowpack and cornices. Wind slabs may be found on all aspects due to variable wind directions. Recent wind has blown from the northeast, forming fresh wind slabs in south to southwest terrain features at higher elevations. 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. This layer may require a very large load, such as a cornice fall, or rapid weather changes to reactivate.
Terrain and Travel
- Carefully evaluate steep lines for wind slabs.
- The likelihood of deep persistent slab avalanches will increase with each day of warm weather.
- Recent wind has varied in direction so watch for wind slabs on all aspects.
- Extra caution for areas experiencing rapidly warming temperatures for the first time.
- Approach steep open slopes at and below treeline cautiously, buried surface hoar may exist.
- Minimize overhead exposure; avalanches triggered by warming or cornice fall may be large and destructive.
Problems
Wind Slabs
Wind slabs may be found on all aspects due to previously strong southwest wind switching to strong northeast wind. Northeast wind is atypical, so you may find wind slabs in terrain features that don't typically have them. These slabs could be touchy, as they may overly a weak layer of surface hoar. Use extra caution as you approach exposed terrain features.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Loose Wet
The snowpack will undergo a rapid change as the freezing level rises and clear skies prevail. For Sunday, loose wet avalanche activity is most likely during the heat of the day on sun-exposed slopes. Cornices will also weaken with the warming trend.
Aspects: South East, South, South West.
Elevations: All elevations.
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 to trigger it would be in thin rocky terrain.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Mar 15th, 2020 5:00PM
