If you find signs of reactivity in the persistent slab share your findings on the MIN, it could save someone else from getting surprised...
Weather Forecast
A series of weak fronts pass over the Park under a SW flow, bringing warm unsettled weather with some precipitation. Tuesday we will see sunny breaks in the morning, followed by flurries in the afternoon/evening (up to 7 cm snow/rain below 2100m). Alpine temps will be a low of -7C, high 0C. Ridge winds will be light (gusting strong) from the SW.
Snowpack Summary
Fresh wind slabs continue to build in high alpine areas. In the upper snowpack a 25 to 80 cm thick slab bridges the March 15th persistent weak layer (facets on polar, sun crust on solar). Recent warming has promoted rounding in the upper snowpack, however the mid and lower snowpack remain weak and facetted from this winters prolonged cold periods.
Avalanche Summary
We received a report of large slab avalanche on Monday in the North bowl of Whistler peak. It was remotely triggered from the ridgetop and failed as a size 2.5 persistent slab (suspect Mar 15th interface), 60cm deep by 75m wide, which ran down to treeline. Some size 1 moist surface sluffing was noted on steep solar aspects on Sunday.
Confidence
Intensity of incoming weather systems is uncertain
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.
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.
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.