Quick report
- Collapsing
- specific
Yesterday's wind event caused the storm snow to become top heavy, making for difficult trail breaking and slow plowing on the downhills. Our field objective today was to see if instabilities in the new and drifted snow will persist on southerly aspects in the days ahead. The answer is a resounding yes on southeast aspects, where we observed numerous collapses on a persistent weak layer (collapsible crust over facets). The answer on south aspects NTL is probably not, though uncertainty increases for above treeline terrain (where we didn't travel and crusts likely thin), and simply because of spatial variability with faceted crust structures. Our two pits on south aspects near treeline showed a crust that was thick and strong enough to support the current load, with no obvious facets above it, and no concerning test results or signs of instability.
Several large collapses (propagating ~50') and a handful of small collapses (propagating ~10'), failing about 2 feet deep. These fit the same pattern: freshly windloaded slopes where the buried 1/23 meltfreeze crust was thin and collapsing into weak facets below, either on SE aspects or low angle S aspects.Weather
- Cloud Cover
- clear
- Wind Loading
- previous
Weekend HST varied from 1' to 3' depending on how it was redistributed by winds. I estimate an average of 20" of settled storm snow. Some light wind drifting on a few alpine features continued today.
Snowpack
The recent snow (~30 to 90 cm, depending on drifting patterns) is still typically fist to fist+ hard, with stiffer slabs in leeward terrain. The 1/23 interface consists of a thin, collapsible crust over facets on SE aspects and a thicker (3-4 cm, pencil hard) crust over facets on steep south aspects. Stability tests on steep south aspects produced non-propagating results in mid-storm density changes. See pit photos.
Avalanche
- Size
- D1.5
- Type
- SS
- Count
- 19
- Aspect
- SE
- Trigger
- N
- Elevation
- 11800 ft
Good visibility! The Ruby Range experienced a natural cycle of soft slabs involving the new and drifted snow over the weekend, typically D1.5 to D2 in size. Yesterday's wind event has obscured some of the evidence and makes it difficult to pin down exact avalanche details. I did not see any step-down avalanches that involved layers deeper than the 1/23 storm interface.