Mt Watson Deep Persistent Slab Avalanche

We had a report of an avalanche that was seen on Mt. Watson from a distance with limited details.  From the photo submitted, we could see that the avalanche failed mid-slope in steep below treeline terrain and thought this could be another deep persistent slab avalanche that had occurred.  Original observation here.  We headed out and tracked down the avalanche on the NE side of Mt Watson.  The terrain here is short, heavily treed, with some steep cliff features.  The avalanche crown was 3 to 4' deep, 250' wide, and ran downslope 100' into the trees with the slope angle at the crown 35-40 degrees.  There was around 4'' of new snow on the bed surface and avalanche debris covering up the scene.  This additional snow was from the Tuesday storm, putting this avalanche occurring most likely on Sunday or Monday Jan 31-Feb 1.  There were multiple visible snowboard tracks in this area and into the start zone where this avalanche was most likely triggered.  The snowpack in this area before our large storm event was very shallow and weak- 1 to 2' deep of faceted snow.  Even though the snow near the ground is still weak, the upper snowpack has gained strength and we had limited unstable snowpack test results on the deeply buried weak layers.  Although small terrain, this area has many trigger points, terrain traps (rocks, trees, cliffs), and increased consequences of being caught in an avalanche.