Boletín de aludes

Boletín de aludes

Payette Avalanche Center
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Peligro de aludes

Alta montaña
3 · Notable
Límite del bosque
2 · Moderado
Bajo el límite
1 · Débil
Desactualizado: este boletín caducó 6 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

The Avalanche Hazard is Considerable today in high elevation, exposed, wind affected terrain.  Human triggered avalanches are likely near ridgetops and on wind loaded terrain where stiff wind slabs formed earlier this week.  Human-triggered avalanches are possible on all steep, protected slopes where weak layers exist under this week's new snow.   Widespread natural avalanches occurred Tuesday night/Wednesday am as a result of rain, wind, and heavy snow.  Slopes that did not release naturally may be waiting for you to trigger them.  Choose your terrain wisely today and avoid steep slopes.  

Problemas de aludes

  • Wind Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Likely
    Tamaño
    1–3

    Earlier this week, peak gusts reached near 40 mph in the mountains near McCall and over 60 mph on West Mountain and swirled around the compass.  Wind loading was substantial with deposition occurring on many aspects.   These wind slabs may also be resting on buried weak layers consisting of buried surface hoar and near-surface facets.  These weak layers will allow even shallow avalanches to propagate over large slopes and across multiple terrain features.  

    Local variations in terrain can influence wind loading on slopes that may not be on your radar.  Red flags like shooting cracks, or hollow feeling, or sounding snow should turn you around in your tracks. Visual clues like sculpted or wavy/dune-like formations will give you a good idea what slopes are affected by winds. Sudden changes in the consistency of the snow surface from soft to hard is another clue that you are on a wind slab.  Wind slabs may have the ability to step down into deeper layers below creating much larger avalanches with much higher consequences.

    Relatively small R2-D2 size avalanche on a wind loaded slope near Fisher Saddle. This had enough of a terrain trap below it that the debris was enough to bury a rider or skier.

  • Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1–2

    The storm that came in Tuesday/ Wednesday this week packed a big punch and left its mark on the West Central Mountains.  A combination of wind, new snow and rain overloaded many slopes during the storm.  Crowns ranging from inches to feet are easy to spot on many aspects.  Several large avalanches occurred mid storm as well and can be seen on wind loaded terrain on many large upper elevation slopes.  Complex crowns wrapping around terrain features and connecting multiple steep slopes are signs of the buried weak layers that allowed easy propagation.  

    A layer of buried surface hoar and near-surface facets is pretty easy to spot in the snowpack around 35-40 cm down from the snow surface.  This is last weeks snow surface and is deeper in wind loaded areas. These layers are reactive in our pit tests and relatively widespread on wind-protected slopes.  While the snow surface seems firm and unlikely to produce additional avalanches in many places, human triggered avalanches should be expected on slopes that did not experience natural avalanches during the storm cycle.  Pay attention to whumphing or collapsing sounds as you travel and avoid steep slopes.  

    This is the bottom of this week's storm slab that is failing relatively easily in pit tests. The larger crystals are well-preserved surface hoar. They are embedded in a layer of near-surface facets. CT8 SC, ECTP14 SC, CPST 45/90 SC

  • Deep Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1–3

    Our snowpack has multiple weak layers right now.  Different aspects have different problems. Solar aspects have complex combinations of crusts and facets while shadier aspects have one or more persistent weak layers that are getting harder to trigger in pit tests.  Almost all aspects have the common factor of very weak, loose, faceted snow in the lower snowpack.   These deep layers are getting hard to trigger in most areas but seem to be more easily triggered in the mountains to the south of McCall.  Several large avalanches that released in weak layers near the ground occurred and were remotely triggered last week outside the boundaries of Tamarack Resort and on Council Mt.  Avalanches triggered in these deep layers would likely be unsurvivable based on the size and density of the slab above them.

                           

     

    January 7 remotely triggered avalanche near Tamarack Resort.

Avalanche Discussion

The storm that came through earlier this week left a lot to be desired,  snowfall totals were less than expected, the rain line was higher than expected and the resulting conditions are less than ideal. Wednesday, we found survival skiing conditions with a punchy, breakable crust on slopes as high as 7700ft.  Thursday, we found nearly all time off-trail sled conditions in areas that were protected from the winds earlier this week.  High ridgelines are very firm, and scoured in many places.  Lower elevation slopes have a brittle crust on them that will be challenging no matter whether you are skiing or sledding.  

Our observations page is growing...Thank you to everyone that has been sending in observations this year!  These help the forecast team form a clearer picture across the forecast area. We will be continuing to improve the observation form to make your submissions even easier over the next few weeks. Photos of recent avalanches are also very helpful to the forecasters with a short description of aspect, elevation, and relative location.

Also, resort and backcountry skiers leaving local ski areas need to be aware that areas outside of the ski area boundary are not patrolled, have no avalanche control work being done in them and if you are injured skiing or caught in an avalanche, the ski patrol has no obligation and may not have the resources to assist you.  Backcountry rescues are subject to the direction of the Sheriff's department and Search and Rescue Teams.  Rescue could be hours away, even close to the ski area.  Self-rescue is your best option and that means that everyone in your party should have the gear, understand the risk, and have the ability to provide an avalanche rescue and to perform basic life-saving medical skills.  The backcountry adjacent to resorts has some of the statistically highest concentrations of avalanche incidents and fatalities every winter no matter where you are.  Thanks to the Friends of the Payette Avalanche Center and our local resorts, you will now see beacon checkers at our backcountry gates.  This is a great reminder of the risks you face when you leave the ski area.