Spooky-Moderate Avalanche Hazard: A reactive layer of surface hoar below the fresh snow is primed for human triggering. Choose conservative terrain and consider that hazard may be most tricky at treeline elevations.
Southerly winds have impacted snow at upper elevations, incoming northwest wind may reverse-load features. There's a lot of loose snow out there, expect fresh slabs to form where the wind picks up.
20-40 cm of snow is poorly bonded to the interface below (a layer of surface hoar) and has been reactive to skier traffic. Keep an eye on the wind, slabs may quickly form wherever the wind encourages the fresh snow to bond; and with a weak layer of surface hoar below, reactive slabs may be more widespread and extend into treeline elevations and be more reactive than expected in sheltered areas.
The "upper" early winter snowpack consists of around 50-70 cm of recent snow over various layers formed mid-November, including surface hoar, faceted grains, and a hard crust. While our avalanche concern is focused on the interface just below the recent snow, we're hoping to gain more information on the distribution and sensitivity of these deeper layers as we collect more field observations.
A layer of surface hoar below the fresh snow continues to demonstrate reactivity. Widespread whumpfing and cracking were reported on both Wednesday and Thursday. And on Thursday, evidence of a natural size 2 avalanche was observed on a north aspect at 2000 m.
A collection of MINs across the forecast region capture the snowpack well: touchy cut banks (MIN1), whumpfing and shooting cracks (MIN2), and reactive snowpack tests (MIN3). The interface of note in these reports is a layer of surface hoar down 20-40 cm, however, MIN3 also found another reactive layer of surface hoar down 75 cm. For now, we lack field observations to determine the distribution of this lower layer, but it is something we will be tracking.
Upwards of 40 cm accumulated around the region over the last few days. This covers a reactive layer of surface hoar now down 30-50 cm. Reports of whumpfing, cracking, and recent avalanches suggest this new snow is not bonding well.
At treeline and above around 50-70 cm of snow overlies a weak layer from mid-November consisting of sugary faceted grains, weak surface hoar crystals in sheltered terrain features, and a hard crust on steep sun-exposed slopes. We have limited information at this point in the season, we're hoping to gain more information on the distribution and sensitivity of these deeper layers as we collect more field observations.
Snowpack depths exceed 160 cm at upper elevations and the latest flurries have covered surface roughness and extended rideable snow into lower elevations.
Friday night
Cloudy with light flurries, trace to 5 cm overnight. Increasing southwest wind 10-20 km/hr. Treeline temperature low -15 °C.
Saturday
Partly cloudy with sunny breaks in the afternoon. Southwest wind 10-20 km/hr decreasing through the day. Treeline high temperature -8 °C.
SundayClear, cold, and calm. Light northeast wind, treeline high temperatures -8 °C.
MondayCold with incoming cloud and wind. Southwest wind increasing to strong. Treeline temperatures -12 °C, wind chill temperatures lower.
More details can be found in the Mountain Weather Forecast.
