Regions
Northwest Coastal.
Confidence
Poor - Timing, track, or intensity of incoming weather system is uncertain
Weather Forecast
Synopsis: The latest models suggest that there is still quite a bit of moisture associated with this storm. West of Terrace should see a lot of rain that may even fall on the peaks late Sunday afternoon. East of Terrace, the freezing level should remain steady around 500m. Temperatures drop in the wake of the cold front which should result in snow for much of the region Sunday night.Sunday Night: Freezing Level: Dropping to around 750m overnight. Precip: 10/30mm - 15/50cm Monday: Freezing Level Average: 750m Precip: 2/4mm - 2/8cm Wind: Mod, W gusting Strong.Tuesday: Freezing Level: 500m Precip: 2/4mm - 2/8cm Wind: Mod, W gusting Extreme.Wednesday: Freezing Level: 1200m Precip: 3/5mm - 4/10cm Wind: Lht. South.
Avalanche Summary
Not much new activity on Saturday. Lots of evidence from last weeks cycle that went to size 3 on the basal facets is still present. It should be interesting to see the results of the cycle induced by Sunday's storm.
Snowpack Summary
Another storm has arrived on the NW Coast and it's picking up in intensity at this time. (Sunday afternoon.) This storm should force the numerous weak layers in our snowpack to show their cards. Total pre-storm snowpack depths in the region vary between 150 - 250cm. On December 20th Kasiks (Between Terrace & Rupert) picked up almost 50cm while Bear Pass saw around 20cm. This snow rests on a variety of old surface layers: old wind slabs, a crust that formed on Dec. 14 in some locations and even small grained surface hoar. This brings the total load of snow on the December 12 layer to 75 - 130 cm. December 12th is a surface hoar/facet combo formed during the early December cold snap which rests on old wind slabs and melt freeze crusts. The last two systems have been accompanied by strong winds out of the South and West which has resulted in a wind slab problem that lingers for a couple of days after the storm. The mid pack is composed of deteriorating layers of old facets and crusts. A significant basal facet/crust combo lingers near the base of the snowpack and is most prevalent on NW - E facing aspects at the upper TL and alpine elevations.
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.
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.