Lawinenlagebericht

West Mountains

Payette Avalanche Center
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Lawinengefahr

Mon
Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
1 · Gering
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Veraltet — dieser Lagebericht ist 8 months ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

Triggering a 1-1.5 feet thick avalanche in wind-drifted snow is possible today. The likelihood of triggering an avalanche will increase throughout the day as a storm brings new snow and wind. While less likely, avalanches in terrain sheltered from the wind can't be ruled out. Small loose snow avalanches involving the new snow will be easy to trigger later in the day. 

Lawinenprobleme

  • Wind Slabs

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

    The current storm has already brought 1-3" of snow, with an additional 3-5" today. Snowfall will be accompanied by moderate to strong winds blowing out of the S/SW. Expect to see wind slabs building throughout the day, growing in size and sensitivity as they do. You're most likely to encounter a wind slab in exposed, upper-elevation terrain, near ridgelines, and on the sides of terrain features such as gullies, ribs, and rolling terrain traps. These features slow the wind down and force it to drop the snow it is carrying.

    As you travel through the mountains today, look for signs that the wind has been at work. Dunes, pillows, and ripples on the snow surface are all indicators that the wind has been transporting snow. If the snow you are moving through is becoming deeper and denser, you're likely moving through wind-deposited snow. Cracks shooting out from your skis or machine are a clear sign of an unstable slab. If the storm delivers more than 5 inches of snow by the end of the day, you may also find storm slabs in sheltered terrain.  A "top-heavy" feel to the snow indicates that soft slabs are forming. Stack the odds in your favor by seeking lower-angle terrain and avoiding traveling above terrain traps such as trees, cliffs, or gullies at the bottom of steeper slopes.

Avalanche Discussion

Snowfall returned to our region overnight and will continue today. If wind could be measured the same way, we have received multiple feet of it, with moderate to strong winds gusting to 20-30 mph. In the past week, we've seen the likelihood of triggering avalanches gradually decrease. Today, we head in the opposite direction. While forecasted snow totals appear to vary from one model to the next, expect that there will be plenty of new snow today to change the picture out there. Your likelihood of triggering avalanches will increase throughout the day as the snow piles up. Today's snow is falling on a variety of snow surfaces, much of which will be a rain crust up to 7,000 feet (and beyond in some locations). Some surface hoar and facets are also likely to have formed in terrain above rain lines and are currently being buried. Any weak snow that has survived in the upper portion of the snowpack will make today's wind slabs more reactive than they would be otherwise. 

In the past month, we've seen the character of the snowpacks in our region diverge significantly with elevation, primarily due to an above-average warming trend and rainfall. Above 7,000 feet, the snowpack is 6+ feet deep in most locations. In contrast, many middle- to lower-elevation locations still have only 1.5-2.5 feet of snow. In both of these examples, older weak layers have either a) become deeply buried and compressed in the upper-elevation case, and triggering avalanches on them is unlikely, or b) permeated with rainfall and have formed what is essentially a frozen cement brick of snow. Thus, our main concern today is the new snow at the surface. 

It's a safe bet that conditions will become more dangerous as this storm progresses. Go into the mountains ready to take a step back from the type of terrain you played in yesterday. Spend a bit of time thinking about the consequences of triggering and being caught in an avalanche in the terrain you are in. Even small slides can have bad outcomes on slopes with cliffs, trees, and terrain traps. 

If you're out in the mountains, submit an online observation HERE. Even simple snow and weather observations can help keep other users safe and help us craft a more reliable forecast for you.

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