High overnight freezing levels and balmy daytime warming should keep persistent slabs near their tipping point Sunday. It will be a great day to soak up the sun in low consequence terrain.
The warmup is testing 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, likely another persistent slab.
The field team saw fresh persistent slabs in Corbin Thursday, part of a pattern of persistent slab activity that was mixed with storm instabilities earlier in the 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 deep releases may occur during the warmup.
A melt-freeze crust or moist snow likely makes up the surface on all but high elevation north aspects. High overnight freezing levels mean crust recovery may be weak. This crust tops the upper part of 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 remain reactive for the duration of the warmup. The lower snowpack is generally well-settled, however a lone deep persistent slab observed Wednesday suggests isolated deep releases may occur during the warmup.
Saturday Night
Clear. 10 - 20 km/h southwest ridgetop wind, easing. Freezing level peaking at 3400 m.
Sunday
Sunny. 0 - 5 km/h west ridgetop wind shifting northeast late in the day. Freezing level falling from 3300 m to 2700 m. Treeline temperature 7 °C.
Monday
Cloudy with scattered flurries bringing less than 5 cm of new snow, easing overnight. 20 - 30 km/h northeast ridgetop wind. Freezing level 1600 m. Treeline temperature around 0 °C.
Tuesday
Sunny. 5 - 10 km/h southwest ridgetop wind. Freezing level 1700 m. Treeline temperature around 0 °C.
More details can be found in the Mountain Weather Forecast.
