Regions
Northwest Coastal.
Spring problems including loose sluffing and cornice failures are the main concern when the sun is out on Thursday. Lingering wind slabs may still be reactive in leeward features in the alpine.
Weather Forecast
Mostly sunny conditions are expected for Thursday with light southerly winds in the alpine and afternoon freezing levels around 1500m. Snowfall is expected to start Thursday night and 10-15cm is expected by Friday evening. Moderate to strong southerly winds are forecast for Friday with freezing levels around 1300m. Another 10-20cm is forecast for Saturday with moderate to strong southerly winds and afternoon freezing levels around 1500m.
Avalanche Summary
On both Sunday and Monday, loose wet avalanches up to size 2.5 were reported in the far north of the region. With the arrival of spring, field observations and data have become quite limited in the region. A lack of avalanche reports does not mean avalanches are not occurring. On Thursday, recently formed wind slabs may still be reactive to human-triggering in the alpine. Solar triggered loose sluffing is possible, especially in places that didn't see sun on Wednesday. Lingering cornices will become weak with afternoon warming and sun exposure.
Snowpack Summary
5-15cm of new snow fell at higher elevations on Tuesday. Strong southerly winds redistributed this snow in exposed alpine terrain and likely formed wind slabs in leeward features. The new snow has buried a widespread melt-freeze crust. With the exception of high elevation shaded terrain, the region has likely returned to melt-freeze conditions on Wednesday with surface melting during during the day and crust formation overnight. The snowpack's strength is directly related to the thickness and strength of these surface crusts. A widespread crust/facet layer from early February and depth hoar at the bottom of the snowpack (primarily in northern & inland areas) are dormant. Cycles of melting and refreezing have limited the reactivity of these old layers. However these layers, or the ground, could potentially once again be the layer for an isolated yet large avalanche with prolonged periods of warming.
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.
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.