We anticipate an avalanche cycle on Tuesday and Wednesday as freezing levels rise to 2500 - 3000 m and the sun comes out on Wednesday. This, plus 5-10 cm of snow and rain to treeline on Tuesday will increase the likelihood of avalanches. Avoid avalanche terrain on both days and expect better conditions starting Thursday as it cools.
Windslabs up to 40 cm deep have been releasing easily from ski cuts, with one report of a skier going for a ride in a size 1.5 that broke 2 meters above them. Expect this problem in the somewhat predictable, leeward and cross-loaded areas at treeline and above.
A 40–90 cm slab sits atop mid-pack facets and depth hoar at the ground. Many avalanches have failed on both layers with wide propagations (persistent and deep persistent slabs). The potential for remote triggering remains. These problems are slow to heal and will remain with us for some time.
Lake Louise and Sunshine ski resorts both reported numerous surface windslabs up to size 1.5 in leeward areas. Additionally, Sunshine reported a large (size 3) deep persistent slab in north-facing terrain at 2500 m elevation that started as a windslab, then propagated a 200 m wide fracture line that ran down into mature timber. This kind of large, deep avalanche should be expected over the next few days with the warm temperatures.
Over the past few days, 15-20 cm of moist (heavy) new snow has been blown into windslabs up to 40 cm deep in leeward areas. This adds to the dense slab, 50-100 cm thick, overlying weak facets in the mid to lower snowpack and is responsible for the recent large avalanches. This condition has been most sensitive in the Bow Summit area, but expect the likelihood of avalanches to increase at all elevations with the warming.
Warm air continues to invade the region on Tuesday, accompanied by 5-10 cm of snow which may turn to rain on Tuesday afternoon. Valley bottom temperatures in Lake Louise will hit +10 on Tuesday and +13 on Wednesday when the sun comes out. Freezing levels will peak on Wednesday between 2500 - 3000 meters.
