Regions
Northwest Inland.
Slight cooling and increasing cloud may take the edge off loose wet avalanche problems on Thursday, but it's still a tricky time to be in avalanche terrain. Get an early start if you're heading out.
Weather Forecast
Wednesday night: Clear. Light southeast winds. Freezing levels remaining near 3000 metres.Thursday: Sunny with cloud increasing in the evening. Light to moderate southwest winds. Alpine high temperatures around +6 with freezing levels easing from 2900 to 2500 metres over the day.Friday: Mainly cloudy with scattered rain showers or wet alpine flurries beginning in the evening. Moderate east winds. Alpine high temperatures around +4 with freezing levels to 2400 metres, dropping to 1500 metres by Saturday morning.Saturday: Cloudy with flurries bringing 5-8 cm of new snow by end of day and light rain below about 1100 metres, easing overnight. Alpine high temperatures around -3 with freezing levels to 1500 metres.
Avalanche Summary
Reports from Monday included an observation of a size 3 (very large) persistent slab running full path and within 100 metres of the viewing platform at Twin Falls. This highlights the current elevated danger in lower elevation areas threatened by large overhead avalanche paths. Please see the Northwest Coastal forecast's avalanche summary for a description of the natural avalanche cycle that is ongoing in this neighbouring region. With limited observations inland, it is advised to treat this activity as an indication of potential in our region.Natural loose wet avalanches have been widespread and reaching size 2 (large), but were confined mainly to solar aspects on Monday. Only small (size 1) loose wet avalanches have been observed on north aspects thus far.Looking forward, expect heightened avalanche activity to continue and potentially expand to all aspects as temperatures remain elevated and overnight cooling remains weak.
Snowpack Summary
Up to 50 cm of settled snow from storms last week sits on the surface. With the help of warm temperatures, this snow has either settled into a slab on shaded aspects or becomes increasingly isothermal (slushy) each day on sun-exposed aspects. Where it exists as a slab, it overlies previously wind affected surfaces, sun crusts (on solar aspects) and weak, sugary facets. The prolonged period of cold temperatures in February had an overall effect of weakening the upper and mid-snowpack, as well as the basal snowpack in thinner areas. These weaknesses are increasingly being tested under the pattern of strong warming currently affecting the region.
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.
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.