Regions
Northwest Inland.
Cloud cover, warm alpine temperatures, localized solar radiation, and rain will deteriorate the snowpack. Use a conservative approach to terrain and watch for signs of instabilities.
Confidence
Poor - Due to the number of field observations
Weather Forecast
Overcast tonight with periods of light precipitation combined with light southwest winds. Freezing levels should drop down to about 1200 metres overnight. Cloudy with light precipitation and light southwest winds during the day Sunday, freezing levels are expected to rise up to about 2200 metres. Moderate precipitation beginning overnight or early Monday morning with freezing levels around 1800 metres. Moderate precipitation continuing during the day Monday, probably rain up to at least 2000 metres. Warm and wet on Tuesday with strong southerly winds.
Avalanche Summary
Slab avalanches up to size 2 were reported in the Mt. Leach area on mostly north facing slopes. On Saturday, touchy wind slabs and storm slabs are likely, especially in areas that receive higher snowfall amounts. If the sun pokes out, solar radiation will be strong and deteriorate the upper snowpack. Watch overhead hazards like cornices, solar triggered loose and slab avalanches.
Snowpack Summary
Recent storm snow has likely formed touchy storm slabs. Strong westerly winds have redistributed this new snow and has formed wind slabs on leeward slopes and behind terrain features. Solar aspects may have a sun crust from recent localized solar radiation. The lack of bond between the new wind slabs and storm slabs over the older snow surfaces buried on April 9 th (surface hoar, crusts and facets) are the primary concern. The March 25th surface hoar / crust layer is reportedly unreactive, however; it should remain on your radar as it may re-awaken with the new load of snow, wind and effects from warming. Large ripe cornices are also of concern and will be a problem with additional loading, especially when the sun and warm temperatures come back.
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.
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 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.