Extra caution is required over the next few days as freezing levels climb into the alpine for the first time this season. Storm slabs are expected to remain reactive on Monday, especially in wind loaded terrain and steep sun exposed slopes.
Summary
Confidence
Moderate - Intensity of incoming weather systems is uncertain on Monday
Weather Forecast
A ridge of high pressure is forecast to keep the region dry until Wednesday. On Monday, mostly sunny conditions are expected with light to moderate alpine wind from the northwest. Freezing levels are forecast to climb to around 2000 m or so by Monday afternoon. On Tuesday, sunny conditions are expected with the potential for valley fog to develop. Alpine wind is forecast to be light to moderate from the southwest. Freezing levels are forecast to reach as high as 3000 m and a temperature inversion will likely develop. A weak storm pulse is expected to reach the region sometime on Wednesday. Freezing levels are forecast to remain above 2500 m and high elevation rain is expected.
Avalanche Summary
On Saturday, natural activity was limited to two size 2-2.5 wind slab avalanches. Skiers remotely triggered a few size 1.5-2.5 storm slab avalanches from up to 25 m away. Explosives triggered numerous storm slab avalanches up to size 3 with typical slab thickness of 50-70 cm. Explosives also triggered one size 3.5 persistent slab avalanche which failed on the November crust layer that had been reloaded following a previous avalanche in early January. On Thursday and Friday, widespread natural and human-triggered storm slab avalanches up to Size 3 were reported throughout the region. On Monday, the recent storm snow is expected to remain reactive to human triggering, especially in wind affected terrain. Extra caution is recommended during the heat of the afternoon, especially on sun exposed slopes. This will become increasingly important through the week as freezing levels remain very high. We are entering the first period of substantial warming following months of sustained cold conditions. Any weaknesses lingering in the snowpack will be tested in the coming days.
Snowpack Summary
40-60 cm of storm snow has typically accumulated of the past few days and is settling quickly due to the warm temperatures. Recent strong winds from the south and west have redistributed this snow in exposed terrain forming touchy wind slabs. Weaknesses may still exist within this recent storm snow with reports of 'upside-down' conditions and easy shears within the storm snow. All this new snow is also bonding poorly to the old interface from early February that includes sun crust on steep sun-exposed slopes, faceted snow, as well as surface hoar on sheltered open slopes. The mid-December surface hoar/facet persistent weakness can now be found down roughly 150 cm. This weak layer has become inactive in the south of the region, but may still be lingering in the northern part of the region near Blue River and Valemount. This layer is expected to get tested with the upcoming period of sustained warming.
rbuhler,
Avalanche Canada
