Lawinenlagebericht

Lawinenlagebericht

Payette Avalanche Center
Auf der Karte ansehen

Lawinengefahr

Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
1 · Gering
Veraltet — dieser Lagebericht ist 6 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

The Avalanche Danger is Moderate today above 7000 ft.  Human triggered avalanches remain possible, especially where a dense slab of snow overlying weaker layers below is thinner and more easily influenced by the weight of a skier or snowmobiler.

New snow and gusty winds  from the WSW-NW have likely created sensitive wind slabs. Pay attention to red flags like cracking and whumphing and changing snow surface conditions.  Be cautious of early season conditions and buried logs and rocks.

Lawinenprobleme

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–2

    The bad problems in the upper half of our snowpack are easily within depth of human triggering. The slab over the weak layer is getting stronger and harder to predict, but everywhere we dig, (even our neighboring avalanche centers are seeing a similar bad set-up) we see the same disturbing bad recipe:

    In the middle of the snowpack , about 2 feet down, exists our layer of greatest concern,  a very weak, loose layer of faceted snow made up of  buried surface hoar and near surface facets that formed during the 3 weak, early December high pressure.   The upper half of the snowpack has been gaining strength, and is resting on a very weak layer below.  We trended from a softer slab to a dense hard slab after the 12/20-12/21 warming and rain event.  Hard slabs are much more tricky to predict and generally have much higher consequences if you do trigger them.  The potential to trigger this type of slab increases where the slab is thinner especially in uneven rocky terrain. 

    On solar aspects and at lower elevation, this layer is preserved under melt/freeze crusts and rain crusts making it even more tricky to predict how it will react to loading.  In the lower elevations, the snowpack warmed more and the rain helped to strengthen this weak layer once it cooled back down making it less of a concern.  

    Many of the natural avalanches earlier this week started in upper elevation, wind loaded, steep rocky terrain, and scoured the snowpack down to the rocks below---meaning that you would get the added bonus of bouncing down a cheesegrater like slope in addition to the very dense blocks of snow pummeling you. 

    This is an easy layer to pick out if you are digging in the snow and also easy to notice if you step out of your skis or off your sled.  Most Steep rocky slopes slid during the natural avalanche cycle Sunday 12/20-Monday 12/21...The slab may support your weight, but chances are you will punch through to the deep bottomless snow below.  This is a layer we will likely be watching and discussing for quite a while.

     

                           

     

    Pit from Saturday above Duck Lake with a fresh crust/facet combo propigating fractures in an extended column.

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1

    Christmas day brought in some notable gusty West Southwest, West, and finally Northwest winds.  Upper elevations could still have sensitive wind slabs up to a foot deep.  Pay attention to Red Flags, and clues of  where the wind deposited, or scoured snow.

    Cracking snow under your skis or sled  or shooting away from your skis or sled are obvious Red Flags.   Wind deposited slabs may be found in unusual places right now and are a major factor that may have the trigger waiting for you.  Visual clues like drifted or sculpted snow will also let you know what the wind has been doing and where.  A sudden change in the consistency of the snowpack from soft to firm or hard  across a slope is also another great clue. You are most likely to find sensitive wind slabs near ridgetops or in other wind exposed areas right now.

     

     

    Granite Mountain Weatherstation

Avalanche Discussion

  Make sure you and all of your partners are riding or sliding with ALL of the essential avalanche equipment and are traveling cautiously in or around slopes steeper than 30 degrees.  Its time to get out, but realize that coverage and stability should drive your decision making. The problems that we have in our snowpack are shallow which allows us to effect or trigger them more easily. As slabs over weak layers gain strength, uncertanty as to its breaking point increases. Hopefully time will heal the weak layers sooner than later? It may take a couple more weeks to a month? Temperatures are forecasted to be cold and clear which could prolong our facet problem.

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.  Also, backcountry skiers and inbound skiers need to be aware of closed areas in or leaving the boundaries at our local ski resorts. The ski patrol closes areas that they deem unsafe and will open them as the conditions change.  Violating closures can result in loss of skiing privileges and can create safety or challenging conditions for patrollers working to open these areas or if they have to rescue you if you get injured while skiing in them.