We are going to be tip-toeing around a touchy surface hoar layer for a while. Periods of sun today may result in loose avalanches and cause trees to shed their snow; enough to trigger slabs up to 55cm deep. Minimize your exposure to avalanche terrain
Weather Forecast
Light snow and moderate-strong winds should back off this morning as a ridge of high pressure builds bringing increasing sun this afternoon. Periods of sun this afternoon may strong enough to cause trees to shed snow and loose sluffing; which will be enough to trigger the surface hoar layer. Mon and Tues will see increasing cloud and flurries.
Snowpack Summary
Another 20cm snow, mild temps, and S'ly winds are forming a soft slab over a widespread surface hoar layer down 35-55cm. It is most reactive where it is largest; between 1700-1900m; or on steep solar aspects where it sits on a crust. Tests indicate it is likely to be triggered by light loads (easy planar/collapses and RB2 whole block).
Avalanche Summary
There continue to be human triggered avalanches up to size 2 on the most recent surface hoar layer. These have occurred on all aspects and elevations, with the avalanches propagating up to 300m wide and traveling fast and far. Yesterday, over 25 size 1.5-3 natural avalanches occurred from steep confined avalanche paths triggered by wind loading.
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.
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.