Regions
Vancouver Island.
This weeks extensive explosive avalanche control and testing at Mount Washington was mostly on cornice features and lee aspects affecting north aspects between 1500 and 1600 meters. These large triggers impacted steep terrain and did not "wake" up the surface hoar instability.
Past Weather
A warming trend and some sun has allowed the snowpack to settle out and become warm.
Weather Forecast
The current northwesterly flow will continue to deliver moderate snow fall amounts and a variety of freezing levels southerly areas within the forecast zone such as 5040 may see freeing levels as high as 2000 meters with norther zones such as Mount Cain may see a rise to a little as 1100 meters. In the wake of this storm front, an artic high pressure will enter the region bring with it clear sky and cooling temperatures. Friday: 10-15cm of snow, Winds Moderate from the Northwest, Freezing levels 2000 dropping to 1200 meters.Saturday: 5- 10cm of snow, Winds Light to Moderate from the South West, Freezing levels 1000 meters.Sunday: No new snow. Winds Moderate from the North West, Freezing levels near sea level.
Terrain Advice
Be cautious when route-finding and transitioning from scoured areas into areas of wind loaded snow.Avoid travelling above or below cornices especially during the period of warming.
Snowpack Summary
Snowpack is settling with numerous layers within the upper and mid snowpack. Testing this afternoon in indicates there is a shear down 75 to 100 cm and this is a surface hoar layer that was buried January 22. The layer is present but no settlement or cracking was felt during travel in unmodified and undisturbed snow. The testing performed did not present as overly concerning, however this layer may be problematic in isolated areas at elevations above 1800 meters.
Snowpack Details
- Surface: Moist and dense.
- Upper: Settled and dense broken precipitation particles.
- Mid: decomposing surface hoar layer down 75 to 100 cm.
- Lower: Well settled.
Confidence
Moderate - Numerous submissions and in field observations and terrain travel provide a good base line for this forecast. Some of the weather models are in conflict and this centers around the freezing levels and timing of the artic cooling period.
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 Dry
Loose Dry avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.