Northwest Coastal

Forecast strong winds and new snow will continue to build a storm slab above buried weak layers.

Moderate - Timing, track, or intensity of incoming weather system is uncertain on Saturday

A parent LOW pressure system off the Aleutians is spinning a band of precipitation up into the north coast. The gradient from the HIGH pressure inland to the LOW pressure offshore is steep, and that means there is a good chance of strong outflow winds overnight. Rain should start to fall on the coast this evening and snow should fall in the coast ranges overnight. Expect 10-15 cm by Saturday morning, with snow and wind continuing during the day. Freezing levels should be close to valley bottoms except on the coast where they are expected to rise up to about 300 metres. A few more cm are expected for Sunday with strong southerly winds developing. Sunday night and Monday look stormy, with strong south winds, 10-20 mm of precipitation and freezing levels rising to at least 500 metres, and probably closer to 1000 metres near the coast.

On Thursday, some small natural avalanches were reported falling out of steep un-skiable terrain northeast of Terrace. North of Stewart one natural avalanche size 3.0 was reported in the alpine on a northwest aspect, and further north and east several remotely triggered avalanches were reported up to size 1.5.

We're dealing with a complex snow pack with multiple buried weak layers in the top meter. Between 15 and 35cm of new snow now is settling into a soft slab that sits above a widespread layer of surface hoar. Snowpack tests have resulted in a mix of easy and moderate results with sudden planar character. Wind effect is variable across the region. A few km north of Terrace we have a report of wind pressed powder in the alpine, while east a little ways the alpine was described as hard wind slab. Areas with more wind are expected to have less buried surface hoar problems.  Below this you can find up to 3 other distinct buried weak layers of surface hoar, faceted snow, or thin sun crusts. These deeper weak interfaces continue to produce variable results in snowpack tests. Forecast strong outflow winds may develop new windslabs on westerly aspects, before the new storm moves in and possibly reverse loads onto north thru east aspects.