Regions
Northwest Coastal.
There is a great deal of uncertainty regarding how the snowpack will recover from recent storm loading and very warm temperatures. I would manage this uncertainty with conservative terrain selection.
Confidence
Moderate - Due to the number of field observations on Tuesday
Weather Forecast
A series of relatively weak Pacific moisture systems will impact the region over the forecast period. On Wednesday and Friday expect 5-10cm of moist snow each day while only trace amounts are expected on Thursday. Freezing levels should drop gradually from 1800m on Wednesday to about 1000m by Friday. Ridgetop winds should remain mainly moderate to strong from the southwest.
Avalanche Summary
A widespread natural avalanche cycle to size 3 took place on Monday in response to recent storm loading and then rain. Avalanche types observed were loose wet, wet slabs, storm slabs and persistent slabs. I'm sure more of the same was observed on Tuesday with rising freezing levels and localized solar radiation. Cooling with help reduce avalanche activity; however, the forecast cooling trend is so gradual it's tough to say exactly when or to what extent.
Snowpack Summary
On Sunday a warm, wet and windy storm added mass and reactivity to recently formed storm slabs. 24 hour snow totals were around 40cm in the Terrace area with closer to 70cm falling in the mountains around Stewart. Rain on Monday, and then rising freezing levels and solar radiation on Tuesday have likely left most surfaces moist or wet. This warming has had a significant destabilizing effect on the snowpack. The January 9th surface hoar/facet layer is down 70-200 cm and remains a concern, especially with heavy and/or thin-spot triggers. Around the same depth you may also find a surface hoar/facet interface from around New Years. There continues to be a lot of uncertainty regarding the reactivity and distribution of this destructive persistent avalanche problem; however, warm temperatures have increased the likelihood of triggering these layers where they still exist. A very conservative approach to mountain travel is still required.
Problems
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.
Loose Wet
Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.