Lawinenlagebericht

Banner Summit

Sawtooth Avalanche Center
Auf der Karte ansehen

Lawinengefahr

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

Kernpunkte

Triggering a large avalanche involving weak snow capped by dense, 2-5 foot thick slabs remains a worrisome possibility. You are unlikely to get direct feedback that the snowpack is unstable; the first sign of instability may be the large avalanche you trigger. Avalanches can be triggered from long distances away from where the slide releases and can break much wider than you might expect. Wet avalanches are possible on sunny slopes this afternoon if the snow surface turns to mush.

Lawinenprobleme

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    2–3

    Layers of weak snow are buried underneath dense, 2-5 foot thick slabs here. If you dig down you'll find facets that resemble early-season weak layers on slopes that face the sun, and crust+facet combinations on sunny slopes. These weak layers produced two remarkable avalanche cycles in our other forecast zones during the two major storms of the past week (map, list). There, we've recorded over 300 avalanches large enough to bury a person in this time, though the actual number of slides likely numbers in the thousands. Observations from this zone are limited, but indicate that these weak layers aren't quite as bad here as they are further south.

    4" of SWE (snow water equivalent) was added to the snowpack here in the past 8 days. This snow has settled into a dense slab that sits perched above the weak layers below. This hefty slab makes it harder to impact the weak layers below and you may not benefit from obvious signs of instability as you move through the mountains. The first indication that the snowpack is unstable may be the very large avalanche you trigger. Avalanches may break much wider than you expect and may be triggered a distance away from the slope that slides. This includes breaking well above you on the slope you are riding or skiing. Tracks on a slope are not an indicator of stability. Avalanches can be triggered after many skiers or riders have traversed a slope.

    (3/12/2023) This avalanche failed on a SE slope at 9000' in Lola Creek. Based on the aspect and the appearance of the crown, this slide likely failed on a layer of facets below a melt freeze crust.

Avalanche Discussion

We are only 3 days out from AVALANCHE WARNINGS and HIGH avalanche danger across our entire forecast area. Very large avalanches (those big enough to destroy your house) were failing naturally just 3 days ago. That information alone should be enough to point you toward conservative terrain today. The persistent slab problem described above is our primary concern today. Here are a few other things to think about as you travel:

  • Rain falling at lower elevations formed stiff, icy crusts in many places. It may feel like you are dealing with a spring snowpack when you walk away from the car to the familiar sound of skins on icy snow or when you are forced to put your scratchers down to keep your sled cool. However, as you climb above the rain line you will quickly find yourself in a cold, winter snowpack. Expect this and plan accordingly; don't let the conditions at lower elevations lull you into a false sense of security. 
  • Temperatures will climb to near freezing today. Cloud cover will mute the effects of the sun, but the same clouds can also trap a lot of heat and help the snowpack to warm up. Be thinking about the possibility of wet snow avalanches if you're finding mushy, wet snow at the surface. You'll be most likely to encounter these conditions in the afternoon at lower and middle elevations on slopes that face S-SW-W. Keep this in mind when planning your exit route for the day. 
  • Cornices have grown to monstrous sizes in recent weeks. These beasts sag and deform during warm temperatures, eventually detaching from the ridges they cling to. Cornices that fail can be very effective triggers for the weak layers described in the persistent slab problem above. 
  • On shaded slopes, the weak snow we are worried about presents as a stack of faceted snow that developed during the extended drought of January and early February. On slopes that face the sun, you'll find a few layers of crusts and facets that were built during periods between storms in late February and early March. The weak layers are a bit closer to the surface on sunny slopes, where they may be slightly easier to impact with your weight.

Temper your ambitions today. This is not a great day to do a big drainage link-up on your sled or to ski the big line you've been eyeing all season. That time will come, but it isn't today. Staying safe in the mountains has required a lot of patience this year, and I applaud your efforts. I can feel my own patience wearing thin. But, the snowpack doesn't much care for how we are feeling, it is on its own program.

When you're traveling through the mountains today you are almost certain to see many large crowns and large piles of debris. Use this evidence to help you imagine the outcome of triggering and being caught in a large slide. While stability is gradually improving and the likelihood of triggering large avalanches is gradually decreasing, the consequences remain the same. The avalanches you trigger today will easily be large enough to bury you, and many will be unsurvivable. Our snowpack continues to behave like a winter snowpack, regardless of the month on the calendar. Follow the snowpack's lead here, she is the boss. 

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