Regions
Northwest Coastal.
Storm slabs will build throughout the day. A MODERATE hazard may be the story in the am, but strong easterly winds and new snow is driving the danger to CONSIDERABLE in the alpine and at treeline by the afternoon.
Confidence
Moderate - Timing, track, or intensity of incoming weather system is uncertain on Thursday
Weather Forecast
Overnight Wednesday: 10-15 mm of precipitation amounts with moderate easterly winds. Freezing levels 1000 m and dropping to 600 m by the am.Thursday: Snow amounts 10-15 cm with strong northeast-east winds. Freezing levels 500 m. Friday: Cloudy with isolated flurries. Ridgetop winds light from the southwest. Alpine temperatures near -3 and freezing levels near 800 m. Saturday: Mostly cloudy with some sunny periods. Snow amounts near 5 cm with ridgetop winds light/ gusting strong from the southwest. Freezing levels near 800 m.
Avalanche Summary
No new avalanche reports on Wednesday.The avalanche hazard will be on the rise with forecast rain, snow and strong winds.
Snowpack Summary
The snowpack consists of a wide variety of snow surfaces including pockets of wind slab, a melt-freeze crust on south-west aspects an wet snow down low, On March 9th, surface hoar and/or smaller facets (on sheltered, shady aspects) were buried by the last significant snowfall down 10-25 cm. The forecast storm snow over the next 2 days will likely have a poor bond to these older snow surfaces.Deeper in the mid-pack, layers of crusts, facets, and isolated surface hoar buried 50 to 100 cm exist from mid- and late-February and a surface hoar/ crust layer from January is buried around 150 to 200 cm. Near the bottom of the snowpack, sugary facets exist in colder and dryer parts of the region, such as the far north.
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.