Bollettino valanghe

Northern New Mexico

Taos Avalanche Center
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Pericolo valanghe

Sun
Alta quota
3 · Marcato
Limite del bosco
2 · Moderato
Sotto il limite
2 · Moderato
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Non aggiornato — questo bollettino è scaduto 7 months ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Open and exposed North and East-facing terrain harbor dangerous avalanche conditions today.  Yesterday's snowstorm built slabs on top of a very weak and widespread persistent weak layer of faceted snow from the early season.  Cracking and collapsing are indicators that you've found this strong-over-weak setup.  Look carefully for these red flag signs and signals before stepping into avalanche terrain, or consider taking a fully conservative approach and sticking with low-angle, wind-sheltered terrain.

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1–2

    Fresh snow totaling 1.0-1.3 inches of SWE for this last storm cycle has built fresh slabs on top of weak snowpack that consists almost entirely of facets and depth hoar thanks to an extended drought period in December.  These slabs are more cohesive and reactive in open and exposed terrain, and less so in wind-sheltered areas.  Look for signs of instability like cracking and collapsing, as these are obvious signs that you've found the strong-over-weak setup.  Stay off and out from underneath avalanche terrain until you're positive that it doesn't contain this setup, as theses conditions make it possible to trigger a persistent slab avalanche from nearby terrain.  Any avalanche triggered could be large enough to injure or bury you while running on or near the ground.

    The crown of a persistent slab avalanche (D1.5) that we triggered yesterday from above the start zone in open and wind-exposed terrain.

    Photo: Charlie Harrison

  • Loose Dry

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1

    Be cognizant of kicking off small sluffs underneath your skis or boards in travels today.  Freshly blanketed slopes all around the compass will be receiving their first sun exposure since the storm today, which will cause a number of dry loose sluffs to release on their own.  These avalanches are generally very small, but can run over significant distances in more sustained steep areas as they gouge into the facet layers and entrain more and more snow.  Even a brief ride downhill could be nasty or injurous, as there are still many ground hazards still near the surface.

Avalanche Discussion

We've been patiently waiting for a significant storm to come our way for over a month now, and the results were fantastic:  10-14" of fresh snow now blanket the mountains near Taos.  This weekend will be a great one to get out and enjoy the fresh harvest under some bluebird skies.  Just remember to bring plenty of extra layers and gloves if you're headed out early this weekend as this high pressure weather pattern brings along some genuinely frigid morning temperatures.  I for one am excited for this come-back in travel conditions and riding quality, but I want to remind those of you reading to tamper your powder fever and think about state of the snowpack before jumping into big terrrain.

Over the month of December, we saw almost no moisture save for a couple inches over the Christmas holiday weekend, which was a significant drought pattern.  It wasn't as bad as the early season drought last year, but the nearly 40 days of high pressure caused plenty of faceting in a snowpack that was never anything but shallow (so shallow that it was hard to even travel around in it).  The point is that the old snow beneath this fresh blanket is VERY weak.  On top of that (no pun intended), this last storm has done two things:  (1.) added weight (1.0-1.3" SWE) to the entire compass, and (2.) on specific slopes, the snow has formed more cohesive slab of snow with more tensile strength.  This strong-over-weak setup is driving our primary avalanche hazard right now.  You're most likely to find it today in areas that are very open and exposed, or those that are seeing wind transported snow.

 

A snow profile at 11,600 feet in open, crossloaded terrain showing poor structure and very easy results.  The December drought facets are very easy to impact, and are leading to easy propagations in areas like this with a cohesive slab.Photo: Charlie Harrison

 

Yesterday, we saw the combinations of these two changes at play in our backcountry.  Our pit results were an obvious red flag with very easy results in the December drought facet.  We were able to get cracking and collapsing easily in open and exposed terrain near and below treeline, and this led to some small to medium slab releases (see photos in gallery).  Avalanche mitigationg teams in the area reported lots of similar results, and although we didn't get much in the way of visibility, we heard reports of a few natural persistent slab avalanches in big terrain at upper elevations above treeline.  At the same time, we didn't get as many signs of instability in more sheltered areas, save for a few smaller pockets.  The difference is that the new snow in these places has added weight but not a cohesive enough slab to cause avalanches, generally speaking. 

The point I want you to take home is that whevever you travel today, you'll be impacting our early season drought facets.  In plenty of places this won't matter because the slab isn't strong enough, but if you happen to be on or underneath an area that harbors the right kind of slab, you could trigger it and the results could be disastrous.  The most suspect area, again, will be big, open, and exposed slopes or those that are actively seeing some wind loading.  The winds have shifted directions today and are currently blowing 10-15mph out of the Northwest on ridgelines as I write, which is enough to transport the new snow on the surface onto different slopes than we saw yesterday.  Approach any open and exposed terrain with genuine caution and focus on what the snowpack is harboring before committing, and be ready to step back!  You can always take a simpler approach and stick to low angle, well-sheltered terrain.  Dry loose sluffs will also be happening easily today as the fresh snow sees sunshine for the first time, so pay attention to those smaller hazards as well.  Have a great weekend, stay warm, and be safe out there!

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