Lawinenlagebericht

Silver Valley & Bitterroot Mountains

Idaho Panhandle Avalanche Center
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Lawinengefahr

Sat
Hochgebirge
1 · Gering
Waldgrenze
1 · Gering
Unterhalb
1 · Gering
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Veraltet — dieser Lagebericht ist 4 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

The return of consistent below freezing temperatures throughout the area has helped lockup moisture that penetrated much of the snowpack last week. 4-5” of soft snow on top of the bullet hard “Lucky Friday Crust” is likely to sluff and entrain dry loose snow on steep slopes (>35°). Winds have had enough energy to transport and deposit available snow into wind slabs on the leeward side of ridges.

Lawinenprobleme

  • Loose Dry

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

    The most recent surface snow does not appear to have setup into a cohesive slab. The 4-5” of light snow sitting on a stout crust is therefore likely to sluff, gather speed, and entrain more snow on steep slopes (>35°). This, in and of itself, is not exceptionally dangerous, however the consequences of being swept off your feet and carried into a terrain trap could be dire.

    Manage this hazard by making good terrain choices and planning ahead. Avoid traveling on steep open slopes directly above cliffs, gullies, or steep strainers (trees). Before dropping in, identify which direction you can ski/ride to safety in the event you find yourself surrounded by moving snow.

    Yesterday, while following the tracks of my two travel partners on a steep slope, I found myself surrounded by moving snow. I was able to slow and move out of the loose dry avalanche while it entrained more snow down slope. Once it had arrested I was able to continue.

  • Wind Slabs

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

    Winds have been strong enough to transport recent snow that has remained soft and lite. Look for wind slabs on north and east aspects at ridgeline. Wind slabs will look like a chalky pillow and sound/feel hollow. Heed shooting cracks in wind effected snow.

Avalanche Discussion

Yesterday we toured from Thompson Pass to Granite Peak. We found 4-5 inches of soft light snow blanketing the “Lucky Friday Crust”, all the way up to the 6,775 ft. peak. The crust is widespread, hard, and supportive. The skiing was better than dust on crust, but you could feel and hear the scrapping on every turn.

Although current avalanche danger is low, we will need to keep an eye on how recent snow and the Lucky Friday Crust bond and react to any new precipitation. Our pits on multiple aspects showed no reactivity in Extended Column Tests (ECTX), but consistent planer failure just below the Lucky Friday Crust during Compression Tests (CT25 Q2). What I take from this, is that the crust is bridging a significant density change beneath it. We have yet to see how the recent snow and any new snow will react on the crust when it is buried deeper.

Last week’s warm temperatures infused much of the snowpack with moisture which has now refrozen and added strength. However, in a pit at 6,600ft on a west aspect I did find a significant (30-40cm) layer of dry weak faceted snow at the base of the snowpack. Again, the Lucky Friday Crust appears to be bridging deeper buried instabilities, but this finding shows that the structure of the snowpack is not uniform throughout the forecast zone. Also, many early season hazards have reemerged at lower elevations since the height of snow diminished last week. Continue to make your own observations about the conditions of the snowpack to inform your travel decisions.

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