Lawinenlagebericht

Lawinenlagebericht

Payette Avalanche Center
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Lawinengefahr

Sun
Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
1 · Gering
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Kernpunkte

The avalanche hazard is Moderate today. Human triggered avalanches are possible.  Multiple weak layers exist in the snowpack above the 3/1 crust and in the February snow which is now 2+ feet down in the snowpack.   

You may also find sensitive layers of wind deposited snow at or near ridgelines.  Sluffing on steep shaded slopes will be something to keep in mind and loose wet activity will increase if the sun makes an appearance today on the sunny aspects.  With increased complexity in the snowpack, use caution as you choose slopes to recreate on today and over the next few days.

Lawinenprobleme

  • Persistent Slabs

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

    Prior to March first, we had not seen propagation in any of our test pits, a stable snowpack for almost all of the season....Now, since March first we have developed poor structure in the upper snowpack that we don't usually see this time of year.

    The snow we received earlier this week fell on a variety of weak layers, including that slick rain crust (Feb 28-March 1 Rain Event), and a layer of faceted snow above the crust that developed over the last 2 weeks. While this slab is made up of the new snow layer, it has now transitioned into a persistent slab problem that will likely stick with us for a while.  Additionally, there is a layer of faceted snow below the crust that developed during the same period of mostly high pressure.  Monday, Kevin was able to remotely trigger an avalanche south of Tamarack Resort on the layer above the crust, and Wednesday,  Dave experienced several large whumps that were likely in the layer below the crust.  Also worth noting are layers of loose, faceted snow that are resting above and below the 2/14 crust. The weak snow on this crust was responsible for a widespread avalanche cycle on 2/28 and 3/1. 

    These layers where they exist are going to be harder to trigger unless you find a shallow spot in the snowpack or are unlucky. If you did trigger one of these deeper layers though it would involve the top 2-3 feet of dense snow.   If you are poking around in the snow in different areas, we would love to see your observations on these layers as there is a lot of variability between different areas.

     

  • Wind Slabs

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

    It is possible that you may encounter areas of freshly, shallow wind deposited snow resting on weak layers below. Winds have gusted into the 20's recently and are forecasted to be light today with some gusts into the 20's.

    Eearlier this week, the winds gusted between 30 and 45 mph throughout the advisory area.  Pillows and drifts have grown below ridgelines but have been mostly non-reactive to ski cuts. Cornices also grew substantially with the high winds and some fresh snow, make sure you give large cornices plenty of respect and avoid the edge.  Pay attention to visual clues near ridgelines and in areas where blowing snow may have been deposited.

    Large cornices and dense snow on the ridgeline above Hum Lake.

Avalanche Discussion

Today's Advisory is sponsored by OnXBackcountry.  Thanks for supporting the Payette Avalanche Center!

March has produced some layers that trump anything we have seen thus far this season. Us avalanche forecasters and snow science people have been getting kind of bored prior to the Natural avalanche/rain event on 3/1...We are definitely not bored anymore. Now we have interesting, spooky results in our test pits. Your snow and avalanche senses should be on high alert today in the mountains. Make sure you and your partners are utilizing best travel practices like watching each other from a safe area on slopes that are steep enough to slide (30 plus degrees). The poor structure that we have seen this past couple of weeks has produced some tests that are indicating a moderately stable or unstable snowpack depending on how and where you look...A lot of slopes slid naturally during storms, so some areas are quite different...variability is truly the name of the game as conditions are dependent upon aspect and elevation. Some rocky ridges are shallow, rotten, or hold no snow at all... Our avalanche hazard is complex and should keep even the most experienced skiers and snowmobilers alert to changing conditions. We have several distinct avalanche problems that each offer a different hazard.

  • Persistent slab:  This week's storm added weight and stress to a buried weak layer on the rain crust from early March.  We are also watching a deeper layer that has been growing and weakening below the Valentine's Day crust. (see pit photos below)95% of our test scores have indicated Moderate to Hard results in propagation in the upper foot/ 3/1 rain crust as well as deeper on the 2/14 Valentine's day crust.
  • Sluffing/dry loose: If you are skiing or riding on steep, shady slopes, you can anticipate sluffing (6-12 inches) in the new snow.  We had some reports of some fairly large sluffs on steep shady slopes Wednesday.
  • Wind slab: Fresh wind slabs were created and were reactive earlier this week. We have not seen any red flags like cracking this week, but be cautious if you see indicators of wind slabs (drifted snow, pillows, large cornices, slabby or hollow feeling snow). Stay clear of steep slopes harboring recent wind slabs.
  • Wet loose: Temperatures have been trending warmer and are rising today and if the sun is out for any length of time it will be affecting and weakening the snowpack on steep solar aspects. Watch for signs of shallow wet loose instability in the form of point releases, roller balls that begin spontaneously or may be triggered if you are riding or sliding on steep slopes facing the sun.