Storm snow sits over surface hoar which remains reactive to human triggers. Watch for deeper deposits in wind loaded terrain. Stick to conservative terrain and be alert for signs of instability.
Monitor snow conditions on sun baked slopes, avalanches become more likely in the afternoon as daytime temperatures rise and sun effect increases.
Around 30 to 40 cm of snow is settling into a slab that rests on large and weak surface hoar in sheltered terrain and old hard interfaces elsewhere. Triggering remains likely and avalanches could propagate widely on this surface hoar layer.
Rising freezing levels and sunny periods will create moist surface snow at low elevations and on sun affected slopes. Wet and slushy snow indicates surface snow is losing cohesion.
Avoid steep sun-exposed slopes during the heat of the day, especially around rocks where warming will be amplified. Cornices may also weaken with daytime warming.
On Thursday natural slab avalanches were observed to size 2, and skier triggered avalanches were observed to size 1. Most avalanches were thought to occur on the buried surface hoar layer, with greater reactivity in wind loaded features. Explosive control work triggered cornice falls that produced slab avalanches to size 2.5 on the slopes below.
Loose wet avalanches were reported to size 1.5 from steep sun affected terrain.
The primary concern is the new snow that overlies surface hoar and/or hard interfaces. As the snow further settles and forms a slab, it is expected to become more reactive. A warming trend with sunny skies could rapidly form slab properties within the storm snow.
30 to 40 cm of storm snow overlies large, weak surface hoar crystals in shaded and wind-sheltered terrain, wind affected snow in wind-exposed terrain, and a hard melt-freeze crust on sun-exposed slopes. Southwest winds have created deeper and more reactive deposits on north to east facing terrain features near ridges. Warmer weather and sunny skies may moisten the snow surface on sun-exposed slopes and at low elevations, which may refreeze into a melt freeze crust overnight.
Another layer of surface hoar and/or weak faceted grains may be found about 60 cm deep, particularly on shaded aspects near treeline.
The remainder of the snowpack is consolidated and strong.
Friday Night
Partly cloudy with moderate southerly winds. Freezing levels drop to valley bottom for most areas, but remain elevated around 1200 m overnight for the immediate coast.
Saturday
Mostly sunny with increasing afternoon cloud. Freezing levels rise to 1400 m, alpine high temperatures of -3 °C.
Sunday
Cloudy with snowfall beginning early morning, 5-15 cm over the day. Moderate southeast winds. Freezing levels reach 1200 m.
Monday
Cloudy with moderate easterly winds. Light snowfall continues. Freezing levels remain around 1000 m.
More details can be found in the Mountain Weather Forecast.
