Avalanche Forecast
Issued: Mar 17th, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs, Persistent Slabs and Loose Wet.
mconlan,
Avalanche Canada
Three things to note: 1) Wind slabs from outflow winds may linger. 2) Buried weak layers remain possible to trigger. 3) Sunny skies may weaken sun-exposed slopes and cornices during the heat of the day.
Summary
Confidence
High - Confidence is due to a stable weather pattern with little change expected.
Weather Forecast
TUESDAY NIGHT: Clear skies, light northeast wind, alpine temperature -3 C.
WEDNESDAY: Clear skies with afternoon clouds, light northwest wind, alpine temperature 0 C, freezing level 1400 m.
THURSDAY: Mix of sun and cloud, light east wind, apine temperature -3 C, freezing level 1100 m.
FRIDAY: Clear skies, light northwest wind, alpine temperature -2 C, freezing level 1300 m.
Avalanche Summary
On Monday, a large avalanche was observed near Shames. Check out this MIN for photos and a description. The avalanche may have been triggered by loose wet avalanche activity and it may have released on the surface hoar layer described in the Snowpack Summary.
Many loose wet avalanches and cornice falls occurred on sun-exposed slopes during daytime warming on Monday. This trend is expected to continue with generally sunny skies and relatively warm air temperature.
Snowpack Summary
Wind slabs and otherwise a wind-affected snow surface exist in exposed terrain at alpine and treeline elevations from predominantly northeast wind. In sheltered features, soft and faceted snow may be found. Clear skies and have melted the snow surface on sun-exposed slopes during the day and frozen it into a melt-freeze crust during nights and cloudy days.
A layer of surface hoar crystals is buried around 30 to 60 cm in sheltered areas at and below treeline. See this MIN from the Shames area that shows this layer when it was on the surface, prior to burial on March 9. There are several additional layers of surface hoar that are now buried 70 to 120 cm and 110 to 160 cm deep.Â
An early-season layer of faceted grains and a melt-freeze crust may linger at the base of the snowpack. A large load, such as a cornice fall, also has the potential of triggering it.
Terrain and Travel
- Carefully evaluate steep lines for wind slabs.
- Avoid steep slopes when air temperatures are warm, or solar radiation is strong.
- Minimize overhead exposure; avalanches triggered by warming or cornice fall may be large and destructive.
- The more the snowpack warms-up and weakens, the more conservative you`ll want to be with your terrain selection.
- Be aware of the potential for large avalanches due to the presence of buried surface hoar.
Problems
Wind Slabs
Wind slabs from recent outflow winds could still be triggered by riders. Use particular caution in steep slopes immediately adjacent to ridge lines.
Aspects: East, South East, South, South West, West, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
Multiple buried surface hoar layers have shown continued reactivity to both human and natural triggers. These weak layers are most problematic at treeline elevations where the surface hoar remains preserved.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Loose Wet
Loose wet avalanche activity is most likely during the heat of the day when clear skies prevail. Avoid overhead exposure on sun-exposed slopes as the snowpack heats up. Note that cornices are also large and could release during daytime heating.
Aspects: South East, South, South West.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Mar 18th, 2020 5:00PM
