Avalanche Forecast
Issued: Feb 18th, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Deep Persistent Slabs.
ahanna,
Avalanche Canada
Forecast strong winds on Wednesday should help keep snow surfaces cool as the sun beats down, but still keep an eye on steep south aspects for signs of solar warming. Watch for fresh pockets of wind loaded snow in lee features as wind slab development resumes in the alpine.
Summary
Confidence
Moderate -
Weather Forecast
Tuesday night: Clear. Light southwest wind. Freezing level valley bottom.
Wednesday: Sunny. Moderate southwest wind, building to strong. Freezing level 500 m.
Thursday: Cloudy with isolated flurries. Strong southwest wind, approaching extreme at ridgetop. Freezing level 400 m.
Friday: Flurries bringing 5-15 cm new snow. Strong southwest wind. Freezing level 800 m.
Avalanche Summary
Human triggered slabs size 1-1.5 have been reported treeline and below, possibly running on patches of buried surface hoar. Over the weekend, natural cornice falls are suspected to have triggered a number of natural wind slabs up to size 2.5 on north to east aspects in steep open terrain around treeline, one of which is described in this MIN report from Friday.
Some very large and destructive avalanches have been sporadically failing on deeply buried weak layers near the bottom of the snowpack, predominantly on north through east aspects in the alpine. On Monday, two deep persistent slab avalanches size 2-3 were triggered from thin snowpack areas by very large loads pushed by snowcats. A few examples of MIN reports of large events during the period of rapid loading by new snow and wind February 8-11 include Hudson Bay, Kathlyn Face, French Peak, Pine Creek Trail, and Babines.
Snowpack Summary
Extensive wind effect in exposed alpine terrain with scoured and pressed windward surfaces and hard wind slab in lees features. In sheltered areas, recent snow may sit over patchy surface hoar or crusts on solar aspects and below 1200 m.
A weak layer of facets that formed during the January cold snap is now about 60-120 cm below the surface while an early season crust lurks at the base of the snowpack. Some large avalanches have been triggered on these layers usually during periods of rapid loading by new snow or wind, and by large loads or from thin, rocky areas.
Terrain and Travel
- Pay attention to the wind, once it starts to blow fresh sensitive wind slabs are likely to form.
- If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
- Avoid exposure to steep, sun exposed slopes, especially when the solar radiation is strong.
- Approach steep open slopes at and below treeline cautiously, buried surface hoar may exist.
Problems
Wind Slabs
Wind slab formation may resume with increasing winds Wednesday with what little snow remains available for wind transport in the alpine. Fresh wind slabs will be especially sensitive to human triggering.
Steep sheltered slopes at lower elevations remain capable of producing human triggered storm slabs particularly in parts of the region where more than 30 cm of recent snow sits over surface hoar.
Aspects: North, North East, East, South East, South.
Elevations: All elevations.
Likelihood
Expected Size
Deep Persistent Slabs
Some very large and destructive avalanches have been sporadically failing on deeply buried weak layers near the bottom of the snowpack, predominantly on north through east aspects in the alpine. The bulk of events occur during periods of rapid loading by new snow or wind, or are triggered by very large loads (wind slab avalanche, cornice or snowcat). Human triggering can be possible from thin, rocky areas.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Feb 19th, 2020 5:00PM
