Northern New Mexico

Triggering a persistent slab avalanche on northwest through east aspects today is still possible. A winter storm should begin impacting the area by early afternoon and as we accumulate snow the avalanche danger will increase. New snow and transportable winds may create drifts 4-6" deep above treeline on the leeward sides of ridges and crossed loaded features by late this afternoon. As we begin to accumulate snow this afternoon we should also begin dialing back our terrain selection. Avoiding slopes greater than 35 degrees today will mitigate the potential increasing avalanche hazard. 

A winter storm is forecast to begin impacting the area by midday/early afternoon. We can expect to see 1 to 3 inches of new snow by 5 pm this evening and 4 to 8 inches of new snow by Sunday morning. Even 3 inches isn't quite enough to increase our avalanche danger alone but with transportable wind speeds or if we see more snowfall than is forecast today we can expect our avalanche danger to increase respectively. In your travels today, keep an eye out for what the weather is doing. As we start to accumulate any more than a couple of inches or you observe wind transporting snow into deeper drifts, I would begin thinking about staying out of avalanche terrain. You are most likely to encounter this concern above treeline where snowfall should begin accumulating sooner and slopes are more susceptible to moderate southwest wind. 

Northwest through East aspects near and above treeline will be the most suspect areas moving forward. It's on those aspects that we have our most concerning snowpack structure. A series of weak layers in the top 20-30cms present immediate failure planes for newly formed slabs to stress. Avalanches that fail on weak layers in the upper snowpack have several options for stepping down in our deeper snowpack. A couple of layers of large-grained facets exist above and below another buried wind slab around 60-80cms down. Any avalanche triggered will have the potential to step down to these deeper weak layers creating a larger more destructive avalanche. 

In long column tests, we continue to get weak layers to fail with easy to moderate force while illustrating the ability to propagate.  So what is that telling us?  Even though it's a "concerning" result and shouldn't be ignored it's still stubborn to trigger an avalanche right now without the addition of a new load.  What these tests are telling me, is that the persistent weak layers have not been healing over the last week and a half. When we do accumulate snow and add a new load (starting late today) these weak layers are going to really struggle to adjust. Here's a great video from Karl Birkeland explaining the importance of adding a load on weak layers.  

Below treeline, our snowpack is entirely faceted. Stepping out of your skis in this terrain will result in immediately plummeting to the ground. There is certainly no shortage of weak snow to be found here. What we haven't been able to sustain all season long though is a cohesive slab and that's exactly what we lack currently. All season long, anytime we have developed a slab below treeline, the faceting process destroys it nearly as quickly as it was formed. As we accumulate snow from our incoming storm we can expect to go through the same process, developing a slab from new snow that increases avalanche danger, then waving goodbye to it as high pressure eats whatever strength it had left for breakfast. Southerly aspects and terrain below 10,000' are incredibly shallow and in a lot of areas, we have returned back to bare ground. Ground hazards and buried obstacles continue to be a concern here.