Avalanche Forecast

Fair - Freezing levels are uncertain on Tuesday

Heavy snowfall is expected to begin sometime early Tuesday morning. The Terrace area is forecast to get about 40 cm of snow at treeline combined with strong southwest winds and freezing levels rising to about 800 metres. The freezing level should drop back down to valley bottoms on Wednesday, however the strong winds will continue as another 20 cm of snow falls at treeline. It looks like the snow and wind will continue into Thursday before a ridge of high pressure dries the area out on Friday. The inland areas around Smithers will get the same pulses of precipitation; however some of the punch will have been left behind in the more coastal areas. Expect about 15 cm from the Tuesday storm, and another 10 cm on Wednesday.

Report of a size 2.0 natural slab avalanche on a northeast aspect at treeline in the Seaton area. The crown was 30-40 cm and propagated about 50 metres across a steep gully feature.

I am going to call the facet layer that is buried about 40cm, the January 20th FC layer. This layer has only been buried a few days, but due to the very cold temperatures when it was buried and the continued cooler conditions during the recent storm, this layer may continue to be triggered by light loads. Tests on this layer in the Seaton Basin are producing moderate shears that are sudden planar in character. Shears that "pop" and slide off the block very easily can give us some clues about the ease of triggering and the extent of propagations. In the Howsons, this facet layered was buried with very little wind effect in the alpine, at the same time that the northeast outflow winds were howling in Terrace. The next storm looks like it will also be cooler, with freezing levels briefly going up to about 800 metres. Cooler temperatures will slow down the settling and bonding process for the weak layer. The new storm has brought about 30 cm to the Interior. The snowpack in the Seaton Basin is reported to be 250 cm at 1650 metres, with a moderate shear down 40 cm on a facet layer. The snowpack depth in the Smithers-Hankin area is about 250-275 cm at the upper extent of the treeline elevation band. Some surface facetting has been observed above treeline, and some surface hoar observed below treeline. Very strong northeast outflow winds have scoured north and east aspects and reduced previous cornice growth. The snow has been transported into stiff windslabs on south through west aspects. These windslabs should be stiff enough in most areas that the forecast southerly winds will not be able to re-distribute the snow. The mid-december crust has been observed to have bonded to the mid-pack in most areas, but may be found to have become facetted in areas with a shallow snowpack. The mid-pack is considered to be strong and well settled in most areas. No basal weak layers of concern have been reported.