Lawinenlagebericht

Lawinenlagebericht

Payette Avalanche Center
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Lawinengefahr

Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
1 · Gering
Veraltet — dieser Lagebericht ist 3 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

Recent snow and wind from both the South and North have formed reactive wind slabs 1-2 feet thick above 7000'. in wind-loaded terrain. Avoid wind-loaded terrain steeper than 30 degrees.

Triggering a persistent slab on weak snow near the ground remains unlikely. 

Lawinenprobleme

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–1.5

    Winds have shifted back and forth over the last 2 days from NW to SW, and now back to NW winds aloft.  Winds were strong Friday and created dense slabs that were reactive enough to bring in 3 observations of shooting cracks where the snow had been wind-loaded. South wind on Saturday morning was strong enough to push snow around, reduce visibility, and fill in tracks in around 15 minutes on No Business Mt, at 7238'.

    Watch for red flags like shooting cracks and sounds like whumphs. Wind loading patterns can be dictated by local terrain and will load and or cross-load and create slabs differently in some places. 

     

    (1/6/2024) Photo: George Halcom

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Unlikely
    Größe
    1.5–2.5

    A wise use of caution on all slopes steeper than 30 degrees as weak layers have been observed in the upper and lower snowpack. Triggering a persistent slab on weak facets from November remains unlikely. We are expecting a significant amount of snow in the mountains all of next week. This new snow will add a tremendous amount of weight (and therefore strain) to upper snowpack weak layers and weak snow near the ground.

    The old November facets have continued to show signs of strengthening. Are they strong enough to withstand next week's weather events? That depends on how much snow we receive and how quickly. That depends on the location and strength of the old snow. The best advice to give is to avoid jumping right onto steep slopes during and right after a storm. Wait for the snowpack to adjust to a new load and remain skeptical of areas in the terrain where this weak snow is most pronounced (steep, north-facing terrain, above 7000').

    ADDITIONAL DISCUSSION

    Over the past week, we have noticed several weak layers in the upper part of the snowpack. Buried surface hoar has been found at multiple locations, buried several inches deep. We've also noticed facets that formed above and below some recent crusts. As this weak snow gets buried by more snow, it may become more reactive. Look for indicators of instability such as shooting cracks or collapsing (whumpfing). 

Avalanche Discussion

New snow that has fallen over the last couple of days as well as over the next week will test the weak snow that exists in our snowpack. The latest storm started on Friday, putting snow on dirt, rocks, and slick crusts which may challenge the bonding of the new snow and present loose snow problems in steep terrain, especially solar aspects where the surface can be slick. The weakest layers near the ground have gained a lot of strength, but are still lacking the structure we like. The snowpack that we have been dealing with has been shallow and minimal, Some places in the mountains below 7,000 feet had dirt a couple of days ago. This drives the formation of weak snow, especially amongst crusts that have formed from the Sun and abnormally warm temps. 

As new snow begins to fall this weekend and next week, what are impatient snow lovers to do? Remain vigilant. Pay attention to snowfall and weather changes. Watch for red flags like rapid loading. Look for obvious signs of instability like collapsing (or whumping) and shooting cracks. Of course, the best signs of instability are recent avalanche activity.

The best way for us to know what's happening as more people are out in the mountains is to submit an observation. Submitting an observation improves your skills, informs other users, and benefits avalanche forecasts. Simple photos highlighting conditions are very helpful.

Did you know there several avalanche classes this month specifically for motorized users? Check out our classes and events page to learn more.