http://www.pc.gc.ca/apps/scond/Cond_E.asp?oID=23025&oPark=100244The persistent slab will be with us for sometime. Adjust your spring skiing strategy accordingly. Despite the moderate rating, there is a low probability of triggering but a high consequence if your wrong. Spatial variability adds to the complexity.
Weather Forecast
Expect 5-10cm Sunday night with -10 Celsius. Monday will be freezing levels of 1500-2000m depending on cloud cover. Could be colder temperatures Monday night as a Northerly wind dominates. Tuesday-Wednesday daytime temperatures may spike up to 2300m with less overnight recovery. This depends on cloud cover. No snow expected. Sun Thursday-Friday.
Snowpack Summary
The snowpack is settling into spring like conditions at TL and BTL on solar aspects. Good overnight recovery with temps to -10 and rising 0 in the alpine by midday. Significant variation in snowpack depth through-out the forecast area with a large proportion being shallow and valley bottoms below 1800m in spring bloom. Basal depth hoar exists.
Avalanche Summary
No field patrol Sunday. Several loose wet slides on solar aspects in the south end of the park likely occurred on Friday when temperatures were higher. Saturday observationed a sz 2.5 on a SW'ly aspect near the Boundary. Large serac collapse on the north glacier of Mt. Athabasca. Cornice failure noted in Marmot Basin backcountry.
Confidence
Freezing levels are uncertain on Tuesday
Problems
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.
Cornices
Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.
Loose Wet
Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.