Travel in avalanche terrain is not recommended due to the likelihood of large destructive avalanches
Last week, large avalanches were running on layers of surface hoar that are now buried 75 - 200 cm deep. The rain will be a big test on the snowpack, potentially overloading these weak layers and resulting in large destructive avalanches.
30-45 cm of heavy storm snow is sitting over a slippery rain crust. It is likely to become over-stressed by added weight from forecast rain, resulting in potential for both human-trigged and natural avalanches.
Loose wet avalanches will become increasingly likely at elevations where precipitation falls as rain.
On Friday a MIN post described seeing several natural avalanches near the Anderson Cabin. Thursday a vehicle triggered a large avalanche in the alpine. It was reported to have failed 1 m deep on a layer of surface hoar. Wednesday two small rider-triggered avalanches and one large (size 2.5) naturally occurring slab were reported near Shames. With rain and warm temperatures in the forecast, we expect to see a spike in avalanche occurrences.
Up to 30 mm of rain is expected to saturate and overload the snowpack. 30-45 cm of heavy storm snow has bonded poorly to a slippery rain crust formed on Christmas. At upper elevations, strong winds from variable directions have likely built reactive slabs on many aspects in open areas and near ridge crests.Two buried surface hoar layers can still be found in isolated areas, buried 75-100 cm, and 120-200 cm deep. The remaining mid and lower snowpack contains several well-bonded crusts. Snow depths are highly variable depending on elevation, and decrease rapidly below treeline.
Friday Night
Cloudy, moderate rain 5-8 mm is expected to mountain top, with the freezing level between 1800-2000 m. 30-50 km/h southerly winds and treeline temperatures around 2 °C.
Saturday
Cloudy, moderate to heavy rain 10-20 mm / which may result in 10-20 cm of snow in the high alpine above 1500m. 20-35 km/h easterly winds, freezing levels between 1800-1400 m, and a high of 3 °C at treeline.
Sunday
Cloudy with no precipitation, 10-25 km/h southerly winds, freezing level dropping to 400 m, and high of -2 °C at treeline.
Monday
Cloudy with 3 cm of new snow, 10 km/h easterly winds, freezing level around 600 m, and a high of -2 °C at treeline.
More details can be found in the Mountain Weather Forecast.
