Bollettino valanghe

Silver Valley & Bitterroot Mountains

Idaho Panhandle Avalanche Center
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Pericolo valanghe

Sat
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 4 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Although the snowpack has been slowly trending toward greater stability, a fragile faceted layer remains buried 1’ to 3’ deep. The potential to trigger a large slab remains possible. Do not become complacent: continue to make good terrain choices and practice safe skiing/riding habits.

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1.5–2.5

    Although it’s showing less reactivity, trigging a large avalanche on a buried layer of weak November snow remains possible. Kevin Davis summed it up well in Tuesday’s Selkirk/Cabinet forecast, “What we're dealing with is a structural problem. We have built our house on a foundation of potato chips.” The layer is widespread, 1’-3’ft deep, and difficult to predict. It is most likely to break in steep (>35°), unanchored terrain and could be triggered remotely from above, below or adjacent slopes.

    The challenge right now is to not become complacent. Pay attention to slope angle, travel one at a time with eyes on your partner, heed whumpfs and shooting cracks and avoid terrain traps. Choose low angle and sheltered terrain for the safest riding today.

Avalanche Discussion

Kyla Berendzen and I toured up Glidden Ridge yesterday. The skiing/riding conditions remain great with lots of soft powder in sheltered terrain. The difficulty right now is not letting a lack of feedback give you false confidence about the strength of the snowpack.

Our season total snow depth remains shallow (100-150cm), which means the buried persistent weak layer is never far from the surface and could be triggered by a skier/rider if they hit just the right spot. Yesterday we performed two extended column tests in the same pit: One sheered on 29 taps (ECTP29) 31inches (80cm) from the surface. The second, a couple feet away, did not propagate. The only difference was that the first column had a rock and cavity buried in the snow right behind it, illustrating that the weak point in the snowpack is nearly impossible to pinpoint, but could be anywhere.

For an insightful explanation of the current conundrum that is our “deceptive” snowpack I recommend reading Blase Reardon’s, Executive Director of Flathead Avalanche Center, Forecast Discussion from yesterday, Thursday Dec. 15th (https://flatheadavalanche.org/avalanche-forecast#/whitefish-range), before deciding to huck into big terrain.

Looking ahead: conditions look like they will remain stable through most of Saturday. Saturday afternoon into Sunday an arctic blast will begin to move into our area from the east, with the potential for frigid temps and significant snow. Remember snowpack likes the weather to be boring: mild temps and little helpings of snow. Dramatic changes in weather are times that avalanche danger increases. Note that forecasts show the winds carrying the arctic blast will be out of the north and northeast, opposite our typical weather pattern, so wind slabs will build in unusual locations.

Call to action: Avalanche professionals rely on weather reports, snotel sites and field days to gather the data needed to build a forecast. But effective avalanche forecasting is a community effort: please submit observations. Don’t be intimidated, you don’t have to be a professional to make observations. Basic information such as: location, snow depth, whumpfs, shooting cracks, wind effected snow, and incidents of natural or human triggered avalanches are all helpful in building a more complete picture of what is happening across the forecast area. Help us help you. So far this season there have been five observations submitted to IPAC by the public. I hope you all have made more than five trips into the backcountry! Thanks for submitting.

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