Northern New Mexico

Triggering a persistent slab avalanche is possible on steep 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 on the slope you plan to ride. Evaluate snow and terrain carefully. Any avalanche triggered could be large enough to bury, injure, or kill a person. 

As we enter 2021, the trend continues of significant storm(s) ( 1-2 feet) and prolonged periods of high pressure in between.  We're currently in another high-pressure period that could be close to two weeks before we see our next snow fall sometime this weekend.  We've been switching back and forth this year from avalanche cycles with storms and loading events, a decrease in avalanche activity as we dry out and continue faceting during these prolonged periods of high pressure. With cold temperatures, no new snow, and a shallow overall snowpack, we're back in the faceting phase that you can read about in the conditions blog.  Each of the last two storms in December produced natural and skier-triggered avalanche cycles as the faceted weak layers struggled to adjust to added weight of the new snow.  

As we push further away from the last loading event on 12/29 the snowpack has been slowly adjusting and the sensitivity to triggering an avalanche has decreased. Our friends at the CAIC wrote a paper several years ago looking at loading events and the frequency of avalanches that occurred following those loading events. Avalanche activity has quieted down for us here in northern New Mexico, and although less likely to trigger an avalanche it's not impossible. It's hard to put any trust in the snowpack we currently have with very fragile weak layers and stiff cohesive slabs on top. Often times immediate feedback like collapses and shooting cracks will not be present. A great example is from the other day when it wasn't until we finished a snowpit and put our skis back on that we got the slope to collapse.  This can apply to riding a slope as 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. 

While out in the field, the question came up about 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 are 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 you 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. It's safe to assume that if you're on a supportable slab, there will be a weak layer beneath.    

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. With the warmest day over the last week and ample sunshine, we may see small point releases on solar aspects in steep rocky terrain that may be able to entrain deeper weak snow. 

Wind-sheltered slopes less than 35 degrees is a great way to stay safe and have fun skiing and riding powder.