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Avalanche Forecast

Archived

Dec 23rd, 2017–Dec 24th, 2017

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

South Coast Inland.

Similar but different!Hazard ratings are for the southern part of the region where storm snow totals range from 80-100 cm. Northern areas that received less snow can expect the same problems but a lower hazard rating.

Confidence

Moderate - Due to the number of field observations

Weather Forecast

SUNDAY: Cloudy, flurries. Accumulation 2-5 cm. Ridge wind moderate from the west. Temperature -9. Freezing level surface. Strong outflow winds near coastal valleys.MONDAY: Mostly cloudy, flurries. Accumulation trace. Ridge wind light from the north. Temperature -9. Freezing level surface.TUESDAY: Mostly sunny. Ridge wind light. Temperature -10. Freezing level surface.

Avalanche Summary

There were no new reports of avalanches on Thursday although whumpfing in hard wind slabs on cross-loaded features at treeline was observed in the northern part of the region. On Wednesday the Coquihalla and Allison Pass areas saw numerous loose dry to Size 1.5, as well as slab and glide avalanches to Size 2 on steep, leeward terrain and smooth rock slabs. Reports from the northern part of the region indicated wind slab activity up to size 2 on north and west aspects in the alpine.In the southern part of the region classic signs of instability such as whumpfing and shooting cracks have also been reported here in the MIN.

Snowpack Summary

The recent storm snow has been redistributed by moderate to strong northerly winds in the alpine and exposed treeline areas, creating wind slabs in some areas and scouring others (particularly in the northern part of the region).The southern part of the region has seen impressive storm snow totals (80-100cm) since Sunday night, compared to northern areas of the region, which received 25-35cm. This new snow sits on crusts of variable thickness that formed on almost all aspects in mid-December (December 15th layer). On steep southerly aspects the crust is supportive, whereas on northerly aspects the crust is quite thin and variable. Beneath the December 15th layer the snowpack is well settled. The late November rain crust is now buried 50-80 cm in the northern part of the region and well over 1 m in the south. Great conditions reports from the north of the region on the Mountain Information Network (MIN) here, as well as from the southern part of the region, here.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Loose Dry

Loose Dry avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.