Warm temperatures have increased the avalanche hazard.
Slabs are now primed to release and smaller avalanches may trigger buried weak layers producing large avalanches.
Three weak layers are buried at a prime depth for human triggering within the top metre of the snowpack. Rain, wet snow, and warm temperatures will increase load on these layers making large avalanches a possibility.
Fresh low density snow is sitting on a variety of weak surfaces that were formed during this past week's cold spell.
Strong southwest winds at higher elevations has redistributed recent snow. Expect to find wind slabs in the alpine and at treeline. They will be thickest and touchiest in lee terrain features.
Heavy snowfall over the weekend has increased avalanche activity substantially producing numerous small and large-scale avalanches.
The majority of these avalanches have occurred naturally from the storm snow. There have been a number of small and large avalanches that people have triggered accidentally. Again these have occurred from storm slabs but several large avalanches that were accidentally triggered by people have slid on buried weak layers.
Warming temperatures will promote slab properties in the snowpack. Slab reactivity is expected to increase in the storm snow as well as the multiple buried weak layers buried beneath.
The top 50 to 75 cm of the snow pack was fairly unconsolidated before Monday's warming event. This is expected to change as warmth may promote slab properties of this top layer. At higher elevations, strong southwest winds will have redistributed much of this snow into fresh wind slabs. Slabs that are formed may not bond well to older surfaces.
Sitting just below this top layer lies up to three weak layers created earlier in December. Some of these may not exist in all areas of our region. The November weak layer, which will continue to be a concern in this warm-up, can be found anywhere between 75 and 125 cm down. The bottom of the snowpack is generally weak and faceted.
With snowpacks such as this, it is important to keep a heads up and know that very small avalanches can become very large very quickly. Check out our forecaster blog to learn about how to manage persistent slab problems.
Monday Night
Mostly cloudy, up to 8 cm accumulation, 25 to 40 km/h south southwest wind, freezing levels between 1500 and 500 m.
Tuesday
Cloudy, 5 to 15 cm accumulation, 25 to 45 km/h southwest wind, treeline temperatures -2 °C.
Wednesday
Cloudy, 2 to 10 cm accumulation in some places, 10 to 25 km/h south wind, treeline temperatures -5 to -2 °C, and freezing levels up to 1100 m.
Thursday
A mix of sun and cloud, trace accumulation, 20 km/h southeast wind, treeline temperatures -8 to -5 °C.
More details can be found in the Mountain Weather Forecast.
