Northern New Mexico

Triggering a persistent slab avalanche is possible on Northwest through SE aspects near and above treeline.  It's on these slopes that you're most likely to find stiff cohesive slabs on top of weak faceted snow. This structure may be difficult to identify on the surface, take the time to dig down into the snow to identify if this strong over weak snowpack structure exists. It's still possible that one of these avalanches if triggered would be large enough to bury, injure, or kill a person. You should seek to evaluate snow and terrain carefully, especially on slopes over 35 degrees. 

Avalanche activity has quickly quieted down since Tuesday where many slopes near and above treeline on North through East aspects avalanched naturally.  Many of these avalanches were able to step down into deeper weak layers and a good reminder that we have a suspect snowpack structure on many slopes that did not avalanche.  Although triggering an avalanche may be more stubborn right now, it's hard to put any trust in the snowpack we currently have. Stiff slabs from previous wind events have fragile weak faceted snow beneath in an overall shallow snowpack (typically less than 1 m of snow).  Playing on hard stiff slabs can be a scary proposition. Often times immediate feedback will not be present and it may not be the first or second person on the slope to produce an avalanche.  These slabs can be supportable until there not, often when you hit a part of the slab where it is thin and you are able to impact the weak layer. 

Working on a research project yesterday out in the field, the question came up when can spatial variability be your friend and when can it be your enemy?  Right now the variability is in our slabs and not our fragile weak layers that very uniform across slopes.  Our slabs on the other hand are present on some slopes, but may not be on others.  They vary in thickness with some slopes I've been on recently having slabs as thick as 1' but quickly taper off down to 10cm in thickness. The variability in the slabs right now is probably some combination of our friend and our enemy in our current snowpack. These slabs don't appear to be well-connected helping limit the size of our avalanches.  Many natural avalanches observed from Tuesday tended to be pocketed and not propagating wide distances across the slope. The varying thickness of the slabs though is concerning in that they tapper in thickness rather quickly, leading to likely trigger points where you may be able to impact those fragile weak layers. The other concern is digging a pit on an adjacent slope might not tell what's happening on the slope you plan to play on right now. To help with this uncertainty assume that any slope that hasn't avalanched is suspect until proven otherwise.  This will mean taking the time to dig down into the snow or using a probe pole to figure out if the slab weak layer combination exists.     

Below treeline, we lack cohesive slabs with mostly a weak shallow cohesionless snowpack.  Ground hazards are abundant and in steep terrain, you may get snow to start to entrain itself creating a loose snow avalanche that could drag you down the slope over a cliff.

Even with all the talk about a poor snowpack structure, there is great skiing and riding conditions right now. Wind-sheltered slopes less than 35 degrees is a great way to stay safe and have fun as we begin 2021!