|Avalanche Details Location: North Face of Battleship, southeast of Ophir State: Colorado Date: 2020/12/19 Time: Unknown Summary Description: 2 backcountry skiers caught, buried, and killed Primary Activity: Backcountry Tourer Primary Travel Mode: Ski Location Setting: Backcountry|
crédito total, Eric Ming
|Number Caught: 2Partially Buried, Non-Critical: 0 Partially Buried, Critical: 1Fully Buried: 1 Injured: 0 Killed: 2||Avalanche Type: SSTrigger: AS – Skier Trigger (subcode): u – An unintentional release Size – Relative to Path: R2Size – Destructive Force: D2.5 Sliding Surface: O – Within Old Snow||Site Slope Aspect: NW Site Elevation: 11155 ft Slope Angle: 30 °Slope Characteristic: Sparse Trees|
This was a soft slab avalanche triggered by the group of skiers. The avalanche was small relative to the path and destructive enough to injure, bury, or kill a person. The avalanche failed on a 15 cm thick layer of faceted snow (SS-ASu-R2-D2.5-O). The crown face of the avalanche was 12 to 20 inches deep and about 700 feet wide. At the crown of the avalanche, the most recent snowfall sat above a firm, wind-stiffened surface that developed during a strong wind event on December 15. Several hundred vertical feet below the crown face, the snowpack was not wind affected, the weak layer was softer, and the slab was more cohesive. This was a Persistent Slab avalanche.There were two avalanches in the main bowl to the east that released sympathetically to the the fatal avalanche (SS-ASy-R2-D2-O)
The avalanche occurred on a steep, northwest through north to northeast-facing slope above treeline, locally known as the North Face of Battleship. The avalanche ran 1600 vertical feet, from the alpine into a below treeline creek bed.
Backcountry Avalanche Forecast
The Colorado Avalanche Information Center’s (CAIC) North San Juan zone rated the avalanche danger as Considerable (Level 3) near and above treeline, and Moderate (Level 2) below treeline. The forecast listed Persistent Slab avalanches as the primary problem at all elevations on west through north to southeast-facing slopes. The likelihood of triggering was Likely and the potential size was Small to Large (up to D2). The summary statement read:
Recent snowfall has thickened slabs above weaker snow inching the snowpack toward its tipping point. Slopes that have not failed naturally may be sitting there waiting for the extra push from a rider or machine. For today, the threat of triggering an avalanche remains elevated and you’re more likely to get into trouble on west through north to southeast-facing slopes. Areas harboring the thickest drifts are the most dangerous and where a small slide could trigger a larger, more deadly one. Strong northwest winds today may help thicken and expand the distribution of wind-drifted slabs below ridgeline and in cross-loaded terrain features.
Treat any steep slope where you see evidence of recent wind-loading, textured snow surfaces, or smooth rounded pillows of snow, as suspect. Although the size of avalanches that you can trigger will be smaller below treeline, these avalanches can be just as dangerous if you are pushed into trees or buried in a terrain trap. Pay attention to surface cracking, audible collapses, and stick to slopes less than 35 degrees to help reduce your avalanche risk.