The fatal incident this advisory is archived for occured near Pemberton which is on the boundary of 2 regions - South Coast and South Coast Inland. South Coast =========== Date Issued: Monday, December 28, 2020, 04:00 Valid Until: Tuesday, December 29, 2020, 04:00 Prepared by ahanna This is an archived avalanche bulletin. New snow is especially sensitive to seeing the sun for the first time. On Monday afternoon you may observe increased reactivity of storm slabs to human triggers as well as solar triggered point releases on steep south facing slopes. Danger ratings Monday Alpine - 3 - Considerable Treeline - 2 - Moderate Below Treeline - 2 - Moderate Tuesday Alpine - 2 - Moderate Treeline - 2 - Moderate Below Treeline - 1 - Low Wednesday Alpine - 2 - Moderate Treeline - 2 - Moderate Below Treeline - 1 - Low Travel and Terrain Advice Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet A moist or wet snow surface, pinwheeling and natural avalanches are all indicators of a weakening snowpack. Be careful with wind loaded pockets, especially near ridge crests and roll-overs. Problems Avalanche Problem 1: Wet Loose What Elevation? - All Which Slopes? - SE through SW Chances of Avalanches? - Likely Expected Size? - 1-2 (Small to Large) With warming temperatures and sun exposure, we can expect to see loose wet avalanches in the new snow, especially on steep south to southwest facing slopes and at elevations where temperatures rise above freezing. Avalanche Problem 2: Storm Slab What Elevation? - Alpine, Treeline Which Slopes? - All Chances of Avalanches? - Possible Expected Size? - 1-2 (Small to Large) 30-50 cm of recent snow has been redistributed at upper elevations by overnight wind from the southwest. Recent snow may become increasingly sensitive to triggering when touched by the sun for the first time. Details Avalanche Summary On Saturday, we received reports from the North Shore mountains of several skier controlled wet loose size 1 and a skier remote size 1 wet slab on a steep unsupported roll. Some whumphing was observed but very little propagation within the storm snow. Snowpack Summary 30-70 cm of recent snow appears to be adhering well to old surfaces. At higher elevations where dry snow fell, strong winds are expected to have deposited deep pockets of storm slab into lee terrain features. Around 50-100 cm of snow now overlies a hard melt-freeze crust up to around 1500 m. This layer varies so widely in depth due to the wind transport of snow as it fell over the last two storms. It seems to be bonding well with surrounding snow. The remainder of the snowpack is well-settled and hosts numerous other melt-freeze crusts which are well bonded to the surrounding snow. Weather Summary Sunday night: Clearing, light southwest wind, freezing level rising to 1500 m. Monday: Sunny, light northwest wind, treeline temperature 0 C, freezing level 1600 m. Confidence - Moderate Uncertainty is due to how quickly the snowpack will recover and gain strength. South Coast Inland ================== Date Issued - Monday, December 28, 2020, 04:00 Valid Until - Tuesday, December 29, 2020, 04:00 Prepared by ahanna This is an archived avalanche bulletin. Keep an eye on steep south facing slopes for solar triggered point releases in recent snow Monday afternoon. Danger ratings Monday Alpine - 2 - Moderate Treeline - 2 - Moderate Below Treeline - 1 - Low Tuesday Alpine - 2 - Moderate Treeline - 1 - Low Below Treeline - 1 - Low Wednesday Alpine - 2 - Moderate Treeline - 1 - Low Below Treeline - 1 - Low Travel and Terrain Advice Minimize exposure to steep, sun exposed slopes, especially when the solar radiation is strong. Be careful with wind slabs, especially in steep, unsupported and/or convex terrain features. Be aware of the potential for large avalanches due to the presence of a persistent slab. Problems Avalanche Problem 1: Wind Slab What Elevation? - Alpine, Treeline Which Slopes? - All Chances of Avalanches? - Unlikely Expected Size? - Small Wind loaded pockets below ridge crests and rollovers may be reactive to human triggers. Avalanche Problem 2: Persistent Slab What Elevation? - All Which Slopes? - All Chances of Avalanches? Unlikely to Possible Expected Size? 2-3 (small - large) Weak layers of surface hoar and/or faceted grains may be found above a hard melt-freeze crust. Recent reports suggest the weak layers may be less prevalent in the south of the region, but still exist in localized pockets. Details Avalanche Summary No recent reports of avalanche activity. A few persistent slab avalanches were reported last week, mostly in the north of the region near the Hurley, but also near Allison Pass. They were triggered by riders, heavy machinery, and naturally. The slabs were generally 60 to 90 cm deep, around 2000 m, and released on the weak layers described in the snowpack summary. Snowpack Summary 5-15 cm of recent snow has seen some redistribution by wind, resulting in good riding quality on lee aspects in the Coquihalla area, according to the great MIN reports we've received. Below treeline, recent snow may be sitting over surface hoar. A hard melt-freeze crust from early December is found around 40 to 120 cm deep in the snowpack. This crust may have weak layers above it, consisting of feathery surface hoar or sugary faceted grains. These weak layers are most prevalent in the north (e.g., Duffey Lake, Hurley) and found to a lesser extent in the south of the region. The snowpack should be treated as suspect anywhere you find either surface hoar or faceted grains above the crust. The remainder of the snowpack is well-settled in the south of the region. In the north, another melt-freeze crust with associated faceted grains around it may be found near the ground. Without evidence of recent avalanche activity, the layer appears to be dormant at this time. Weather Summary Sunday night: Partly cloudy, light southwest wind, alpine temperature -7 C, freezing level valley bottom. Monday: Sun and cloud, light northwest wind, alpine temperature -4 C, freezing level 500 m. Confidence - Low Uncertainty is due to the limited number of field observations.