Reactive storm slabs continue to build at higher elevations. At lower elevations, loose wet and wet slab avalanches are likely.
The danger rating reflects the forecast for the Southern part of the region. Elsewhere, avalanche danger may be a step (or two) lower.
Storm slabs will continue to develop throughout the day at elevations where precipitation falls as snow. Storm slabs are especially likely to be triggered in steep or convex terrain and in wind loaded areas.
Loose wet avalanches will become increasingly likely as rain soaks the snowpack at lower elevations.
Continued rain and higher freezing levels are making the upper snowpack very unstable. Wet slabs are releasing easily and sliding on a firm melt freeze crust buried below. Reports indicate this is specific to the Southern part of the region.
Strong southwesterly winds result in an onshore flow of a cool, and unstable air mass. This brings moderate to heavy snow at upper elevations to a drying and cooling trend by Thursday.
Tuesday Night: 10-20 cm of new snow with strong southerly winds. Freezing levels 1400 m falling to 1000 m by the morning.
Wednesday: Another 5-10 cm of snow with freezing levels 1000 m to 1500 m. Strong southwest wind continues.
Thursday: Drying and cooling trend with the freezing level dropping to 900 m with light northwest winds at ridgetop and clearing skies.
By early Tuesday afternoon, reports from the southern part of the region saw a widespread natural wet loose and wet slab cycle up to size 3. A few glide slab releases also occurred up to size 1.5. These avalanches may have actually occurred on Monday. In the northern part of the region, snowballing was seen from below treeline elevations. No new reports from the southern half of the region.
On Monday, natural loose wet avalanche activity was observed size 1-2 at low elevations throughout the region. In the Pemberton Valley, storm slabs size 1-2 were observed initiating at 1600 m and running 1000 m, entraining wet snow. In the Duffey Lake area, a natural size 1.5 wind slab triggered by a cornice failure was observed on a NW aspect in the alpine.
Storm snow continues to accumulate over a variety of surfaces including surface hoar and/or facets in shady, wind-sheltered areas, sun crust on solar aspects, and hard wind slab in the alpine. Deeper deposits building thicker slabs exist on leeward slopes at upper elevations. The snow is becoming moist/wet and rain-soaked at lower elevations producing wet loose avalanches.
A crust that formed in mid-February is now down around 30-50 cm in the north and 70-90 cm in the south. Recent snowpack tests have shown resistant planar results on this layer in the Duffey Lake area. Another crust/facet layer from late-January is buried down 40-120 cm and has shown no results in recent snowpack tests.
