Expect to find deep and touchy wind slabs that could form large avalanches. Persistent slabs may also linger in specific terrain. Conservative terrain travel is recommended.
Expect wind slabs to be reactive on Wednesday, capable of producing large avalanches with good propagation. Recent strong southwest wind formed wind slabs in lee terrain features. Around 10 to 20 cm of new snow on Wednesday will rest atop these slabs.
We continue to see periodic avalanches on a weak layer of surface hoar and facets buried about 100 cm deep. Resulting avalanches have propagated for hundreds of metres, with some being remotely triggered from hundreds of metres away. The common trend is that they are on north to east aspects around 1500 to 1700 m in elevation.
We received reports of numerous small to large (size 1 to 2) wind slabs triggered by riders and naturally in lee terrain features over the past few days. Slabs on Tuesday were 30 to 50 cm deep around treeline and propagated widely.
On Friday, a large avalanche was triggered by riders, likely releasing on the weak layer described in the Snowpack Summary. See this MIN for details and photos, highlighting the propagation potential and high consequence nature of this layer.
Looking forward, wind slabs will likely remain triggerable by riders on Wednesday. Expect to find them in lee (north to east) terrain features at all elevations. It also remains possible that riders could trigger a persistent slab avalanche, where the layer exists.
10 to 20 cm of snow is forecast for Wednesday with southwest wind. This snow will fall onto previously wind affected snow. Tuesday's strong southerly wind affected the snow at all elevations, forming wind slabs at least 30 to 50 cm deep in any lee terrain feature. Substantially deeper and harder slabs are expected on alpine lee slopes, perhaps around 100 cm. Windward (southerly) slopes were stripped from the strong wind.
A hard melt-freeze crust that extends up to about 1700 m is now on the snow surface in wind-exposed terrain and otherwise buried about 50 to 80 cm in wind-loaded terrain. The crust appears to be bonding to the snowpack.
A weak layer of surface hoar and facets may be buried about 80 to 120 cm deep on north to east aspects in alpine and upper treeline elevations. The layer may rest on a harder melt-freeze crust. Where preserved, this layer has shown to have very high propagation potential and capable of producing large avalanches hundreds of metres wide.
Tuesday Night
Cloudy with light snowfall, accumulation 2 to 5 cm, 30 km/h south wind, treeline temperature -10 °C.
Wednesday
Cloudy with snowfall, accumulation 5 to 15 cm, 20 to 30 km/h south wind with valley outflow winds possible, treeline temperature -9 °C.
ThursdayMix of sun and cloud with intermittent snowfall, accumulation 1 to 3 cm, 30 to 40 km/h southwest wind, treeline temperature -8 °C.
FridayMostly cloudy with light snowfall, accumulation 2 to 5 cm, 40 to 60 km/h southwest wind, treeline temperature -6 °C.
More details can be found in the Mountain Weather Forecast.
