On Wednesday, touchy storm slabs are expected in the high alpine. Extra caution is also required on all sun exposed slopes if the sun comes out in full force.
Confidence
Low - Due to the number of field observations
Weather Forecast
Wednesday is currently expected to be mainly dry with a chance of sunny breaks. Alpine wind is expected to be light to moderate from the southwest and freezing levels are expected to be around 1300 m. The next pulse of precipitation is expected to arrive Wednesday overnight or Thursday morning and 30-40 mm is currently forecast between Thursday morning and Friday morning. Ridgetop wind is expected to be moderate from the southwest on Thursday with freezing levels around 900 m. Friday is currently forecast to be mainly dry with the next storm system arriving Friday overnight or Saturday morning.
Avalanche Summary
No new avalanches have been reported, but it should be noted that the warm, stormy weather has been discouraging backcountry travel and obscuring visibility into alpine terrain so observations have been very limited.On Wednesday, stability is generally expected to improve as temperatures drop. However, if the sun comes out, it can quickly destabilize the snowpack on sun exposed slopes. In the high alpine above the rain line, any recent storm snow is expected to remain touchy, especially in wind loaded terrain.
Snowpack Summary
Heavy rain has saturated the upper snowpack at all but high alpine elevations after roughly 50mm of precipitation fell over Sunday night and Monday morning. Any new snow that may have accumulated at high alpine elevations is likely to remain reactive to human triggering over the short term. At higher elevations, lingering potential may exist for loading from rain or snow to promote reactivity at the late February interface, roughly 1.5 metres deep. This layer is composed of a sun crust on southerly aspects and surface hoar on shaded aspects. An avalanche on this layer would be large and very destructive. No concerns exist below this interface and the snowpack at treeline and below is generally well settled and strong.
Problems
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.
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.
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.