Active persistent slabs and skyrocketing alpine temperatures are a bad mix. Time to back off from avalanche terrain entirely.
Forecast warming will test 30 cm and 50 cm-deep layers below the recent storm snow as well as the January crust 80 - 130 cm deep. Smaller avalanches may also step down.
These layers have produced numerous recent avalanches.
High freezing levels and solar warming will work to destabilize snow on steep slopes sheltered from the wind. Moist or wet snow may shed naturally or with a human trigger and loose releases may trigger more destructive slab avalanches.
We have an initial report of a natural size 3 avalanche in the Little Sand area on Friday. More details soon.
The field team saw five new persistent slabs in Corbin Thursday, part of an ongoing pattern of persistent slab activity that was mixed with storm and wind slabs earlier this week. Activity has been on a range of aspects, mainly in alpine.
A natural size 3 deep persistent slab was also seen Wednesday, suggesting isolated full-depth releases may occur during the warmup.
A melt-freeze crust moist or snow now glazes the surface on solar aspects and potentially to mountaintop by Saturday afternoon. High overnight freezing levels mean crust recovery may be weak. This process will affect 30 to 60 cm of settling recent snow that is wind-affected in alpine. About half of this overlies a crust formed early in the storm. It otherwise overlies faceted snow.
A weak layer of preserved surface hoar or facets from late January is buried 80 to 130 cm deep. This weak layer is expected to stay reactive as warming tests the snowpack. The lower snowpack is generally well-settled, however a lone deep persistent slab observed Wednesday suggests isolated deep releases may occur during the warmup.
Friday Night
Partly cloudy. 20 km/h southwest ridgetop wind. Freezing level remaining near 1800 m.
Saturday
Becoming sunny. 20 km/h southwest ridgetop wind. Freezing level rising to 3300 m, remaining high overnight. Treeline temperature 5 °C.
Sunday
Mainly sunny. 5 - 10 km/h southwest ridgetop wind, easing. Freezing level 2700 m - 3000 m. Treeline temperature 6 °C.
Monday
Cloudy with scattered flurries, negligible accumulation. 20 - 30 km/h northeast ridgetop wind. Freezing level 1500 m. Treeline temperature around 0 °C.
More details can be found in the Mountain Weather Forecast.
