Northern New Mexico

Heightened avalanche danger exists today on East, North, and West aspects where you may find a fresh, cohesive slab sitting atop abundant weak snow.  Our snowpack harbors widespread persistent weak layers that are being stressed by snowfall and wind in the last 24 hours, so be on the lookout for a strong-over-weak snowpack structure that could produce a slab avalanche.  Cracking and collapsing are obvious red flag signs that you've found this unstable structure.  Keep in mind that any avalanches triggered today could be large enough to bury or kill a person.

After weeks of waiting, we finally got our first significant snowfall for the month of February, a welcome Valentine's Day treat.  Storm totals are about 4-7 inches in the mountains, but the storm came in warm and wet, so the local accumulations are elevation-dependent and the snow is a little more dense than we're used to seeing mid winter (about 10% on average).  Adding to the inch of snow we saw on Thursday, this is a decent amount of moisture (0.5"-0.75" SWE) that we've added to our mountain snowpack in the last several days.  This will be quite helpful to improve travel in the mountains, but we'll also start to see some avalanche activity again as this new snow has added some stress to our widespread weak layers and reintroduced a more cohesive slab in some terrain.

Today you should be actively looking for a strong-over-weak setup, especially if you're getting up higher in elevation where the most snow has fallen, including areas below treeline.  The storm came in with some winds in the 15-20mph range, so you should be on the lookout for stiffer, more reactive slabs if you're heading out.  There's some uncertainty as to the degree of reactive slab development, but any of this is concerning because we have widespread persistent weak layers on all northerly and East-facing terrain, in addition to the usual West-facing chutes near Williams Lake.  Well-developed near surface facets sit right below the new snow on colder aspects, while more solar aspects hide a not-so-strong crust with really weak facets just below that.  In places where the new snow has formed a more cohesive slab, it would be most likely to propagate on one of these upper layers of facets that are very close to the surface.  In addition, our December drought depth hoar will continue to be at play - we've had propagating test results on this widespread layer recently so it's possible to see any smaller slab avalanches step down to this layer and propagate much more widely.  We saw this happen on multiple occassions during our last storm cycle, and this layer of depth hoar has only continued to grow and weaken since then. 

In totality, this storm ended up being a bit smaller than the last two storms, but we saw plenty of avalanche activity with both and similarly to today, they followed long drought weather periods.  Earlier this week, ski and boot penetrations were at or near the ground with all the faceting occured during this most recent drought.  So a prudent take-home message to you today is this: it will be very easy to impact our abundant weak layers in travels today, so wherever you're finding more of a slab, you could trigger a persistent slab avalanche.  Keep your focus on the changing snow underfoot today and pay close attention to any feedback (whumpfs or collapses) that you're getting from the snowpack.  If you suspect a strong-over-weak setup on any terrain greater than 35 degrees, consider staying off of it.  There's more snow and potentially some extreme winds on the horizon for next week, so conditions will continue to change in the coming days.  Stay safe out there and enjoy winter while it's here.