Southern San Juan

Snowpack

Becs Hodgetts · Mar 13, 2021 · Southern San Juan

Weather

Squalls of heavy snow coming through, some gusts blowing snow from trees below treeline. In near treeline terrain, wind was light, but seemed to be picking up at road level when I got back to the car.

Snowpack

Travelled on south, north and northeast below treeline. Traveled on northeast near treeline (11600').The recent dust layer was evident on all aspects up to 10cm deep. South below treeline HS varied form bare ground to 1m deep. A breakable 1cm thick melt freeze crust sits over a soft 5cm layer which then sits on a 5-10cm thick (pencile to knife) hard melt freeze crust. Quick hand pits did not show any percolation columns, however the entire snow pack has rounded and is transitioning to a spring snowpack. A very rapid warm up could produce problems on steep below treeline slopes if water hit the basal depth hoar, but a slow seasonal warmup will not. Only around 3 inches of new snow was bonding well to the old snow/crust surface - so far. With maybe a foot or more new snow (which is not forecast) we may see small storm slab avalanches from steeper slopes. I dug on a northeast sheltered form the wind at 11600'. The buried near surface facets were present, but not reactive in snowpit tests I think due to the soft slab above. As other forecasters have noted, this layer would be reactive with a stiffer slab above it. Making the most likely place to trigger an avalanche on this layer any wind drifted slope facing NW- N-NE where this stiffer slab exists below the new snow. ECTN18 - no propagation - below this buried buried nsf layer, and a compression test revealed an unenthusiastic, resistant planner N24 result, both at the late December weak layer. Where I travelled below treeline it will take a significant load (~1.5-2"SWE) to increase the avalanche danger.