Regions
Northwest Coastal.
Confidence
Fair - Due to variable weather conditions
Weather Forecast
A continued low over the Gulf of Alaska will whirl a series of convective and synoptic systems into the southern part of the province, bringing remnants of those systems to the northern regions. The bulk of the precipitation will arrive Thursday-Friday, with continued bands of fast moving clouds, light precipitation and sunny breaks later Friday into Saturday. Thursday: Snow amounts near 5-10 cm. Ridgetop winds strong from the South, potentially blowing over 100km/hr. Alpine temperatures -4, freezing levels near 1100 m during the day then dropping to valley bottom at night. Friday: Snow amounts 5-10 cm. Ridgetop winds moderate from the South. Freezing levels valley bottom. Saturday: Occasional light flurries and cloud cover. Sunny breaks expected with intense solar radiation during those times. Freezing levels are expected to be near 600 m.
Avalanche Summary
On Tuesday, numerous reports of loose wet avalanche activity occurred. These all occurred on solar aspects up to size 2. Explosives control (using 75kg charges) produced several avalanches up to size 2.5. West aspects were targeted, at 900 m. These did run to ground surfaces, and left up to 2.5 m of debris on the road. Unsettled weather conditions are forecast. It's important to pay attention to weather, and it's influence on the snowpack when recreating in your local mountains. I suspect the period will be fairly cloudy, but if periods of sun shine through, beware of solar aspects.
Snowpack Summary
Moderate to strong southeast winds have created wind slabs on opposite slopes and terrain features in the alpine, and treeline. I expect this to continue through Thursday with cranking Southerlies all day. Spring-like conditions have existed over the past several days. This has formed crusts on solar aspects at all elevations that become moist under sunny skies during the day. Melt-freeze conditions exist on all aspects below 1000 m. This has developed a well settled upper snowpack with no significant layers of concern. New surface hoar growth up to 10 mm has been reported on sheltered North aspects. Forecast snow may initially have a poor bond to these new surface forms (crusts, surface hoar). Below all this, down 60-120 cm exists a very spotty surface hoar/ facet interface. Operations from the field noted no recent activity on this layer. I suspect it's becoming dormant, but would be suspicious of large triggers like cornice fall, or under the weight of a sled and it's rider in specific areas. Cornices in the region are reported to be very large and potentially unstable.
Problems
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.
Cornices
Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.
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.