Northern San Juan
AvalancheAmy Pertuz · Feb 4, 2022 · Northern San Juan
Weather
COLD. The 6" which fell in this zone Tuesday night into Wednesday mostly remained in place, but mod NW winds at ridgetop level Thursday were creating drifting in lee areas in specific areas above tree line.
Snowpack
The new snow from Wednesday measures 6" in this area, and came in upside down, with a prominent density change 3" below surface (F on top of F-...) Dry-loose slides were seen on all aspects and elevations, but the largest and longest-running were seen on W and NW aspects NTL, Two small, recent (in last 7 days, likely Weds morning?) slab avalanches were seen in the area, both occuring within areas that slid during the new year's cycle. As both were shallow, it does not appear that they ran on the same old basal facet layer as the prior slides. On a N aspect NTL, a very shallow slab (est 10") about 40'x40' had released recently in surface snow. It is possible this ran on 0121 surface hoar, which was widespread and fairly well preserved in this area. The very small and shallow nature of this avalanche points to a very weak layer that such a small and non-cohesive slab above it could still trigger it. SS-N-R1D1 NTL N aspect. Nearby, in Governor basin on an ENE aspect ATL, another small but deeper-looking slab had also released naturally within the last week, and likely within the last couple days. This slab was entirely contained within a much larger, explosive-remote-triggered slab avalanche that was triggered around the new year. The depth of this is estimated at 16" from a distance. Based on prior observation, it still does not appear that this new slab ran on the old basal weak layer, rather a shallower one, as much of this path had filled back in. Hard saying, though. While larger, this was still a small slab, SS-N-R1-D1 ENE ATL. The area around this slide receives wind-deposition and also maintained preserved surface hoar into the ATL reaches.
Avalanche
Numerous dry loose all aspects and elevations with the largest being on W-NW-N aspects NTL SS-N-R1-D1 NTL N aspect, shallow surface slab SS-N-R1-D1 ATL ENE aspect, surface slab but deeper, appears over 1ft deep