Avalanche Observation

Front Range: Peak 3 to 4 ridge

Human triggered avalanche (presumably HS-ASu-D2-R2-O) and close call along the ridge line from Peak 3 to Peak 4 (~4100′, presumably SW aspect).

One human caught and carried briefly, but able to escape off the slab.  One dog caught and carried, but uninjured.

The involved party’s report: It whumphed deeply and then propagated across the entire bowl feature with a crown ~4′ in center and tapering to ~10″ near the flanks, estimated at ~150-200′ wide.  It was triggered from ~20 degree slope, but the slope angle at the crown was ~40 degree.  Seemed to be persistent slab that failed at faceted layer between old wind slabs.

Approximate location at yellow diamond in center of photo:

Looking up at the crown:

Some size perspective:

Another view, looking towards Peak 4.  This avalanche start zone is a repeat offender.  It has been triggered multiple times unintentionally and intentionally; it releases relatively reliably when stressed from the typical thin and weak trigger point just to the looker’s left of the apex of the crown.

This photo shows the trigger point (circle).  The party was practicing safe travel rituals, and only exposing one at a time.  The human trigger was booting from the X along the dashed line to the O trigger point.  The human trigger was able to crawl and roll off the slab back towards the rock outcrop near the X.

The triggering party estimates the slide to have run ~1000′, possibly triggering another slide as it descended.