Northwest Coastal

Fair - Timing or intensity of solar radiation is uncertain

Tonight and Friday: The whole Coast is under a high pressure system and the front affecting the Northern part of the region should move out tonight. Light precipitation will end tonight North of Stewart, the dry trend continues in the South. Moderate to strong wind from the SW will switch from the S. Temperatures will rise as well as freezing levels up to 3000 m (or 2000 m further North) with a mix of sun and clouds during the day.Saturday: A weakening frontal system will reach the coast which should bring moderate precipitation and strong S winds switching from the SW in the afternoon. Freezing levels are expected to lower to 1400 m. with the arrival of the snow.Sunday: Ridge of high pressure rebuilds over the coast leading to a clearing trend with mild temperatures.

There was an avalanche cycle yesterday at all elevation and on all aspects. Multiple natural releases up to size 4.0.  Most of these avalanches would have run on the early January surface hoar layer buried under the storm snow at treeline and below treeline in all the region and some on the deep persistent basal facet layer in the alpine in the Northern part of the region.

The increased solar radiation and warming trend for tomorrow is driving the avalanche danger. The intense heat will weaken the surface of the snowpack and most likely increase avalanche activity on all aspects, but especially on S and SE aspects slopes when the sun comes out. There is a possibility that loose wet or slabs could step down to deeper instability, especially in the Northern part of the region.In the North, the early January surface hoar buried at around 1 m deep at treeline and below treeline is showing to be a main concern since it has proved to be very active during the last storm, even on low angled terrain. The basal facets also became reactive in the last rapid loading. These are found in the alpine and at treeline under over 2 m of snow in some areas. The persistent weak layers mentioned above are also found in the Southern part of the region,but are not showing as much reactivity.  The extensive windslab formation that happened during the SW wind event have most likely started to bond to the underlying surface in the alpine and at treeline. However, expect steep crossloaded or steep lee features to weaken during the day especially if the sun hits those slopes.