Regions
Northwest Coastal.
Confidence
Fair - Timing, track, or intensity of incoming weather is uncertain on Thursday
Weather Forecast
Tuesday: Mainly sunny with no precipitation. Moderate outflow (easterly to northerly, low elevation) winds easing. Freezing level around 700m during the day and valley floor at night. Warm alpine temperatures.Wednesday: Light precipitation as a weak system approaches the coast late in the day. Light southerly winds. Freezing level rising to around 1000m. Thursday: Moderate precipitation associated with a frontal band is forecast, with some uncertainty about amounts and timing. Light to moderate south-west winds. Freezing level rising to around 1500m.
Avalanche Summary
A few cornice falls have been observed over the past couple of days. Wind loading led to a localized avalanche cycle near Stewart on Sunday. Several solar-triggered avalanches have been observed on sunny slopes during the heat of the day.
Snowpack Summary
Strong winds from the east and south-east have created new slabs at treeline and above. Temperatures have been unseasonably warm, leading to moist or wet weak surface snow conditions. Where a re-freeze has occurred, a crust now exists. Recent storm snow appears to be well settled. A facet layer buried on Jan 20th still exhibits hard, sudden planar results in isolated snowpack tests. It's about 120-150cm deep in the snowpack. Cornices will be weakest during the heat of the day and have the potential to act as a trigger for deep avalanches on the slope below.
Problems
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.
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.
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.