Northern New Mexico

Today you can trigger a dangerous avalanche where recent snow and winds have formed a cohesive slab on steeper slopes that held snow prior to Friday's storm, which are primarily on North and East aspects.  This last storm added a significant amount of weight to our weak, shallow snowpack, overwhelming facets and depth hoar that have formed during the dry winter we've had.  As you move up in elevation, there is the potential for larger avalanches that break wider and take most of the season's snowpack along with them.

Stick to lower angle terrain below 35 degrees today and expect to get frequent audible whumpfs and shooting cracks in your travels, as our snowpack is primed for human-triggered avalanches.  Stay off and out from underneath large steep slopes today, as these conditions lend themselves to remote triggering. 

It's shaping up to be a beautiful, sunny day in the Northern Sangres now that the atmospheric river event has fully moved out.  The mountains picked up another inch or so of convective snow yesterday, but this doesn't change my forecast discussion much as the main topic is the overall significance of this last storm, which has had a big impact on the stability of our snowpack.  The avalanche danger remains Considerable at all elevations today.  Please be cautious and make conservative decisions if you're taking advantage of the nice weather today and getting out, as avalanche terrain remains a dangerous place to be on or near.  Here is why.

Extremely weak snow pervades the Northern NM snowpack after 3 months of weather dominated by drought and shallow overall snow depths.  Large facets and depth hoar crystals can be found all throughout the oldest parts of the snow that date back to November 8th, and in many cases the snow that fell between then and Friday (though there isn't a whole lot of that).  Easterly and northerly aspects that held on throughout the extensive drought show this trend the most dramatically, and the weak snow hasn't showed any signs of healing even with record-breaking temperatures in early February.  Below treeline, these weak layers are fairly close to the snow surface and easiest to impact as a traveler.  Near and above treeline, greater exposure to the sun and strong wind events have built and sustained melt-freeze crusts and hard slabs on or close the old snow surface, and the faceted weak layers are a now a bit further down.  These areas can hold a bit more of the weight from this last storm but are still struggling to adjust to the new load.

In the last two days since the storm hit, it couldn't be clearer that our snowpack has been primed for human-triggered avalanches.  We've continued to experience widespread collapsing and cracking in our travels and seen some impressive natural avalanches up to size D2 from the last 48 hours in below treeline terrain.  Avalanche mitigation teams have also produced some impressive results up to size 2 in uncompacted terrain, speaking to the same overall picture: in the backcountry, we have built fresh slabs that are overstressing the incredibly weak depth hoar and facets in our snowpack.  This is a widespread persistent slab problem that may not improve for some time.  Right now, persistent slab avalanches will generally be the easiest to trigger below treeline where the layers of facets and depth hoar are closer to the surface and easier for you to impact.  These avalanches won't break incredibly deep but they can certainly propagate widely, as I witnessed yesterday scoping out a natural avalanche crown that I estimated to be about 250 feet wide.  In terms of the higher elevation terrain, the potential avalanches will be larger and break deeper, but they may also be harder to trigger.  This is because the melt-freeze crusts or hard slabs in between the new slab and the faceted snow can hold a bit more weight.  That said, you should definitely not underestimate these deeper areas in higher elevation terrain.  Looking out at some of the big pieces of terrain near and above treeline yesterday, I saw minimal signs of natural avalanches, and I'm interpreting that to mean that these areas are just waiting for a little extra weight to trigger.  Don't let that trigger be your backcountry group.  This avalanche problem is the most dangerous that we currently face and it's worth approaching it with serious caution over this holiday weekend.

Wind slabs are also important to discuss really quick.  The atmospheric river event loaded different slopes variably because it came through with such intense and gusty winds.  The winds eased off yesterday but continued to blow moderately throughout the day and we witnessed some large plumes forming across ridgelines in the afternoon.  Wind slabs are a concern on their own and if you're getting up high today you should be cognizant of the signs and symptoms of a wind slab: drifted pillows, textured or unusually shaped snow, etc.  But the big concern is these slabs will be thicker and heavier than the slabs in more sheltered areas, an additional stress to our persistent weak layers.  If you come across the signs of a wind slab in leeward terrain today, consider that there's a increased chance of triggering the slope on the facets or depth hoar, or that a smaller wind slab avalanche could easily step down to these deeper weak layers and lead to a more destructive slide.

If you're getting out into the backcountry today, keep it simple and stick to a conservative tour plan.  Carefully evaluate the snowpack and back off as soon as you get the sure-fire signs of instability like loud audible collapses or big shooting cracks.  Be cognizant of the potential for remote triggering today, meaning you might be standing on relatively flat terrain but could trigger an avalanche above you.  It's best to give large steep areas or known avalanche paths a wide berth.  The good news is that travel conditions have improved in a lot of places in the wake of the storm.  Enjoy the snowy mountains over this long weekend and please be safe!