Lawinenlagebericht

Lawinenlagebericht

Payette Avalanche Center
Auf der Karte ansehen

Lawinengefahr

Mon
Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
1 · Gering
Veraltet — dieser Lagebericht ist 4 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

The avalanche hazard is Moderate today. Human triggered avalanches are possible.  Multiple weak layers exist in the upper two to three feet of the snowpack. Persistent slab avalanches will be difficult to trigger but the size would be destructive. The weight of a snowmachine is more likely to impact these deeper weak layers than the weight of a person.

Small, wind slab avalanches will become reactive today with the recent storm snow and strong winds yesterday. You may also find sensitive wind deposited snow at or near ridgelines. Watch for clues that indicate wind direction and pay attention to how the snow changes with the terrain. 

Lawinenprobleme

  • Persistent Slabs

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

    In some locations, we have a decent slab overlying a persistent weak layer. This weak layer is composed of 1-1.5 mm facets sitting on or near the interface from the 03/01 storm that produced rain up 7800'. We have not seen a persistent weak layer problem all season long. It may surprise people to be dealing with a persistent weak layer problem this late in the season, but this problem warrants your attention. We have received multiple reports throughout our advisory area of reactivity on buried weak layers in our upper snowpack. With a little bit of new snow yesterday and last night, there is additional stress on these weak layers.

    Triggering a persistent slab avalanche will be difficult unless you find a shallow spot in the snowpack (see video). However, the consequences are fairly high as an avalanche would involve the top 2-3 feet of dense snow.  There is a lot of variability with these persistent weak layers. The sensitivity may vary depending on aspect and elevation. Below 7800' exhibit caution on steeper slopes that face the northern half of the compass. Pay attention to collapsing of weak layers like the sounds of whumpfing. If you experience a collapse, stay off of steep slopes in that terrain.

  • Wind Slabs

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

    You can expect wind slabs to become more reactive today. Our advisory area saw anywhere from 2-6 inches of snow in the past 12-18 hours. Winds were moderate to strong out of the W/SW yesterday through the afternoon. Last night, the winds shifted out of the NW and eventually north. Wind-deposited snow could be up to a foot deep in some locations at or near ridgelines. Pay attention to visual clues near ridgelines and in areas where blowing snow may have been deposited.

Avalanche Discussion

Today's advisory is sponsored by Mile High Powersports just South of McCall on highway 55, Thanks for supporting the PAC and the Friends!

Although today's advisory reads moderate, this is a different kind of moderate than what we've been dealing with over the past few months. Since early January, we have experienced little in terms of significant snow. Over the past few months, the avalanche hazard would rise and fall in conjunction with incoming storms. You may remember reading about shallow wind slab avalanches or dry loose avalanches. Within the past week, we are now dealing with a different type of moderate. This is when it's time to pay closer attention to the avalanche problems (listed above). A persistent slab problem presents different challenges than a wind slab or dry loose avalanche. Persistent slabs are more difficult to trigger and are much more destructive. These buried weak layers lurk under feet of snow and can make it seem as they are not present most of the time. Now is a good time to be digging into the snow. Take a few moments to look for these buried weak layers and see if they exist in the particular terrain you are wanting to recreate in. I would be alert to activity on buried weak layers on slopes below 7800' that face east through west on the northern half of the compass. You are more likely to experience collapsing or whumpfing than you are shooting cracks. Collapsing of a buried weak layer is a red flag and you need to adjust your terrain selection accordingly if you experience any red flags.