Lawinenlagebericht

Galena Summit & Eastern Mtns

Sawtooth Avalanche Center
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Lawinengefahr

Tue
Hochgebirge
3 · Erheblich
Waldgrenze
3 · Erheblich
Unterhalb
3 · Erheblich
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Kernpunkte

Both human-triggered and natural wet snow avalanches are likely today. Conditions will become more dangerous as warm temperatures and brief periods of sun melt the weak crust on the surface of the snow. Be ready to retreat to gentler terrain (or your vehicle) as the crust on the surface breaks down. There is a small chance of triggering a dry slab avalanche on very steep, wind-exposed, shady slopes.

Lawinenprobleme

  • Loose Wet

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

    An extended period of above-freezing temperatures is creating a range of wet snow avalanche problems. You are most likely to encounter wet snow problems during the heat of the day, but thanks to consecutive nights of very weak/absent freezes, conditions may be hazardous earlier and later as well. The slide pictured at right/above occurred yesterday at 6:30PM. In addition to warm temperatures today, we also have a chance for rain falling on the snowpack, which will exacerbate any wet snow problems.

    Temperatures have been warm enough that the snow has become wet even on upper elevation slopes that face away from the sun. You can encounter wet snow problems on any slope that has snow on it and even on dry slopes with snow above them, as the photo at right/above illustrates. Today's list of wet snow problems includes wet loose avalanches, wet slab avalanches, and cornice failures. Any of these can produce a slide large enough to bury you today. Please read the Forecast Discussion below for more details on all of these.

    (3/27/2022) This sizable wet snow avalanche occurred at 6:30 PM on Sunday, 3/27 in the Warm Springs Creek drainage. It started on a NE-facing slope at 6,500' and carried some large debris with it as it traveled down the slope. Photo: B. Smith

  • Persistent Slabs

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

    Triggering a dry, persistent slab avalanche has become unlikely—but not impossible. The last triggered slides were over a week ago (photo), but the weak layers responsible for these avalanches still exist in middle and upper elevation shady terrain. In some locations, these layers have become moistened by meltwater that is percolating through the snowpack and these slides will have the character of a wet slab, described in the Forecast Discussion below.

    Where is there still a lingering chance of triggering a persistent slab avalanche? On shadier, very steep (over about 35 degrees) slopes where past wind events and warm temperatures have built a stiffer, denser slab. 

Avalanche Discussion

Today is the 6th day of an extended period of well above average temperatures. Unfortunately, last night's freeze was the weakest of this entire period. Cloudy skies overnight prevented the snowpack from radiating out the heat that it absorbed during the day and the crust on the snow surface will be thin and weak. Because of this, wet snow problems will quickly become an issue as the day warms. In addition to warm temperatures today, we also have a chance for rain falling on the snowpack, which will exacerbate any wet snow problems. Here is a look at the type that you might encounter today:

WET LOOSE AVALANCHES: In many locations, the snowpack is deeply saturated with the meltwater that has been generated in the past 6 days. Because of this, any loose snow avalanche that is triggered or that releases naturally is likely to gouge down into the pile of wet, mushy snow below. This type of slide can involve most or all of the seasonal snowpack and these slides can become large and destructive quickly. Take a look at this photo of one such slide that released naturally yesterday at 6:30 PM in the Warm Springs Creek drainage to get a sense for what these will look like. That slide only had about 500' to pick up steam, you can imagine how large these can become in bigger terrain.

WET SLAB AVALANCHES: These types of slides occur when water percolates through the snowpack and weakens the bonds at weak layers in the snowpack. On Thursday I spotted a large, destructive wet slab that released on an E/SE-facing slope at 9,700' in the Boulder Mtns. Yesterday, I went to check in on our weak layers on north-facing slopes and found that even at 8,700' these weak layers were becoming wet thanks to the very warm temperatures. You can read my observation for more details and to see photos of the snowpack I encountered. Predicting the timing of wet slab avalanches is notoriously challenging.

CORNICES: Remember December and early January, when it snowed for days on end? I do, but it feels like a lifetime ago. During that period, large cornices formed in many locations. Warm temperatures are allowing these huge chunks of snow to gradually melt, and they are creeping and sagging downwards as they do. This adds stress to weak spots where the cornice is attached to the ridge and can cause the cornice to break off and tumble down the slope below. When this happens it can entrain large amounts of wet snow. I spotted a cornice that had done this in the Sawtooths on Thursday (photo). Similar events are likely today.

If you head out into the mountains today, pay close attention to how well the snow surface has frozen overnight. Flip your pole around and try to push it through the crust, or hop off your machine and see if you can kick through it with your boots. Keep in mind that the snow surface at the trailhead is likely to be the best freeze you will see. As you travel above the inversion and into a snowpack that hasn't seen as much melting through the season you can expect to find a much thinner, weaker crust. This crust is about the only thing that is holding the snowpack together and it is likely to break down quickly again today.

Wet snow avalanches become less predictable when the snowpack fails to refreeze. You are most likely to encounter wet snow problems during the heat of the day today, but its a good day to have your guard up from the time you leave your car to the time you get back. In my personal travels over the past week, I've been progressively stepping back from avalanche terrain. Yesterday I chose to avoid avalanche terrain entirely and I plan to make the same choice today. We will be seeing much safer conditions and better skiing and riding when the snowpack has a chance to refreeze more deeply.

You can catch up on what happened this past week and hear a little more about warm temperatures and melting snow in Ethan's latest Weekend Update!

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