Northern New Mexico

New snow and strong winds will continue to keep dangerous avalanche conditions at upper elevations.  A stretch of 10 days of snow and wind has created  4 to 6-foot cohesive slabs on many slopes. These slabs will be stiffer and deeper at upper elevations on the leeward sides of ridgelines and cross-loaded terrain features. Triggering an avalanche near the surface can be large and dangerous on its own, but could also step down into deeper weak layers near the ground and in the middle of the snowpack.  These deep persistent slab avalanches would be very large and most likely unsurvivable. Avoid slopes that are actively loading or where you notice obvious signs of instability like shooting cracks or loud audible collapses. Sticking to wind-sheltered, lower-angle terrain without steep slopes overhead will provide safer and better riding conditions. 

It's another cold start to the morning, with temperatures below 0 and in the single digits. Snowfall picked up yesterday afternoon and ended early this morning where we picked up an additional 4 to 6 inches of snow.  The string of consecutive days with measurable snowfall is now at 10, where we've picked up over 4 plus feet of snow and 5 to 7" of snow water equivalent (SWE). Over the last 5 days we've had moderate to strong westerly winds that look to continue through the weekend into next week.  Today will bring a return of the sun, and temperatures warming into the teens and twenties. Another low pushes into NM later this evening bringing more snow later tonight into Sunday where we could pick up an additional 2 to 4 inches.   

Whether you want to call it storm or wind slabs, moderate to strong winds and continued snowfall have led to a stiffening and thickening of slabs that are easily deeper than 4 feet deep at upper elevations on the leeward sides of ridgelines and cross-loaded terrain features. The strong winds and dense heavier snow with the second AR event have led to a mostly upside-down set-up within the storm snow. Stiffer, firmer snow on the surface rests on top of lower-density snow from earlier in the week during the first AR event.  With such strong winds, you may encounter more loading than you might expect further down the slopes.  At upper elevations, these slabs will be hard and may feel supportable on the surface, which can lead to avalanches breaking in unexpected ways, oftentimes well above you.  Most avalanches triggered will take place within the new snow but could create a one-two-punch scenario where a large avalanche within the storm snow, steps down to create a very large avalanche on deeper weak layers. 

The persistent weak layers near the ground that has plagued us much of the season are facing a significant test from the wet heavy snow, and will need time to adjust to this significant loading event. SWE totals over the last week from the two AR events are at 5 - 7" . For context, we had less than 5" of SWE for the water year on January 1st at the Snotel Powderhorn site. This has been a significant amount of loading as the SWE from the last week of storms accounts for about a third of the total water we've received this year. Many slopes released naturally during the storm, producing very large avalanches running long distances well into the valley bottoms. Even slopes where weak layers were deeply buried and dormant may be more reactive with this added weight.  Near and below treeline terrain is where depth hoar near the ground continues to linger and remain reactive in a relatively shallow snowpack (< 1.5 m) prior to last week's storm.  At upper elevations, there's still a threat of triggering an avalanche near the ground, but most slopes have a deeper snowpack where impacting these layers would be more difficult but may not be impossible with such a significant amount of loading. In the middle of the snowpack, small-grained facets sandwiched between harder slabs and faceted crusts have been observed but are not widespread.  Most of these layers have been found on north and easterly aspects near and above treeline.  These storms over a week period will be the biggest snowfall events of the season and may push us to where we see deep persistent slab avalanches that would be unsurvivable.  Recent very large avalanches during the storm should serve as a good reminder of what the consequences could be if you were to trigger a persistent slab avalanche. 

It's a strange time for the middle to end of March. Very cold temperatures, that are 10 - 20 degrees below average, 10 straight days of snow for us here in the desert southwest, and more snow on the way, it doesn't feel much like spring except for the typical strong to moderate winds. This is still very much a winter snowpack, and with more snow and cold temperatures in the forecast, it could be into April, before we start to transition to more of a springtime snowpack.   Avalanche conditions will continue to remain elevated through at least the weekend.  Sticking to lower-angle wind-sheltered terrain without steep slopes overhead will help you avoid many of the avalanche problems.