We're heading into a period of warming and its effects are uncertain. Expect stability to deteriorate over the day as the snowpack heats up. The east slope of the region could see the greatest impact.
The recent storm created large wind slabs across exposed leeward and crossloaded terrain. Many size 2-3 wind slab releases have been observed in recent days. Choose routes that minimize your exposure to these looming hazards - they may remain reactive to human triggering.
Forecast strong winds may continue to form small but touchier new slabs with any snow still available for transport.
Our deadly persistent slab problem appears to have been put to rest in snowfall hotspots in the west of the region, but the east slope is less certain. Forecast rapid warming could also produce surprising natural avalanches on this deep weak layer. Keep your guard way up in the east of the region and think of surface avalanches, cornice fall, or the weight of a machine as a trigger for this problem.
Warm temperatures and periods of strong sun will destabilize the upper snowpack in coming days. Start and finish early to reduce your exposure and be mindful of overhead terrain exposed to the sun. Larger wet loose avalanches or cornice falls could also trigger deeply buried weak layers.
WEDNESDAY NIGHT: Clearing. Moderate to strong south winds.
THURSDAY: A mix of sun and cloud. Light south winds increasing to strong over the day. Alpine high temperatures to around -1 as freezing levels jump to about 2000 metres.
FRIDAY: Mainly cloudy with flurries increasing in the afternoon. Moderate to strong south winds shifting southwest. Alpine high temperatures around -2 with freezing levels to about 1700 metres.
SATURDAY: Cloudy then clearing, with 5-15 cm of new snow from the overnight period. Moderate southwest winds. Alpine high temperatures around -7 with freezing levels back to about 1400 metres.
The weekend and early part of this week was an active period for avalanches in the region. Some highlights include:
-Monday's explosives control yielding numerous wind slab avalanches, generally size 2-3 (large to very large).
-A widespread natural avalanche cycle to size 3 in the Table River and Sentinel Pass areas, also observed on Monday.
-A size 3 natural persistent slab triggered by a wind slab release in Pass Creek, snapping trees in its path.
-This MIN report from Sunday showing a widespread touchy 25cm storm slab interface avalanching on anything over 30 degrees in the Pine Pass area.
-3 natural avalanches, the largest likely near size 3 burying the Alberta side Kakwa trail, near Kakwa Lake
Looking forward, we are heading a period of warming that should be a couple notches greater than what we saw on Monday. In some areas, high freezing levels will be amplified by strong sunshine. Over the next few days, backcountry travelers will need to manage a mix of lingering, large wind slabs, wet loose avalanches, and an uncertain persistent slab problem that hasn't been conclusively laid to rest by recent weather, especially on the east slope.
We have variable new snow totals from the weekend of up to 90 cm in Pine Pass, 50-70 cm in Sentinel Pass, 60 cm in Renshaw (including a pulse prior to the weekend), 70 cm over the previous crust in Torpy, and a less impressive (estimated) 25 cm in the Core Lodge area. Kakwa seems closer to a 5-day 30 cm. This snow has undergone significant transformation from strong south winds in exposed areas and from freezing levels reaching about 1600 metres on Monday.
We now have roughly 90-110 cm overlying a weak layer of faceted snow (and potentially surface hoar) from mid February, as well as another especially problematic, slightly deeper, widespread persistent weak layer from late January/early February that consists of surface hoar. This layer is now about 120-160 cm deep in some of our snowfall hotspots. It is most prevalent around treeline elevations, but likely reaches into the alpine and in openings below treeline too. These layers are both significantly shallower in the east of the region.
A couple of point observations from Torpy and Bijoux on Monday and Tuesday are beginning to suggest a scenario where a combination of natural avalanche activity, melt-freeze cycles, and the massive weight of our recent storm snow has done a great deal to either flush out or stabilize our persistent slab problems in the west of the region (think Pine Pass to Renshaw) The situation is less certain on the east slope, where significantly less storm snow likely leaves these problems within the reach of human triggering, with a bit of added consequence from their increased depth.
