Regions
Northwest Coastal.
New snow, wind, and fluctuating temperatures are on the menu for the next couple days. Choose conservative terrain until the new snow has a chance to settle and bond.
Confidence
Fair - Timing, track, or intensity of incoming weather system is uncertain
Weather Forecast
Synopsis: A center of low pressure crosses the region on Friday resulting in moderate precipitation – 15-25 cm. The freezing level should be around 500 m and winds are moderate to strong from the west. The weekend looks mainly cloudy, cooler, and a bit drier. Expect 5-10 cm each day – maybe a bit more later on Sunday. The freezing level is at valley bottom. Ridge winds are light to moderate from the southwest-southeast, but we could see strong outflows develop in the coastal inlets and valleys on Sunday.
Avalanche Summary
There have been no reports of avalanches for the past few days. Watch for fresh, touchy wind and storm slabs to develop over the next couple days.
Snowpack Summary
Strong outflow winds earlier this week left a variety of wind affected conditions in exposed terrain at all elevations. You will likely find wind pressed snow on north aspects, thicker wind slabs on south facing features and some degree of cross-loading on everything else. At and below treeline widespread surface hoar was reported, which may become an issue once its buried by new snow. Some areas experienced light rain or freezing rain early on New Years Day which could lessen or eliminate this problem. The mid December crust can be found down around 30 to 80 cm and is sandwiched with facets and surface hoar. The mid November crust down 70 to 175 is gaining strength but is still reactive in test profiles. It is likely trending towards dormancy.
Problems
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.
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.