Lawinenlagebericht

Central Sierra Nevada

Sierra Avalanche Center
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Lawinengefahr

Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
2 · Mässig
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Veraltet — dieser Lagebericht ist 9 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

The avalanche danger remains MODERATE due to some wind slabs lingering in near and above treeline terrain and the potential for loose wet avalanches as the day warms up.  Some isolated persistent slabs may also linger in some near and below treeline areas, especially in the Carson Pass and Ebbetts Pass regions. 

Lawinenprobleme

  • Loose Wet

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

    More warm weather today will cause loose wet instabilities including roller balls, pinwheels, and point release avalanches to become possible on steep sun-exposed slopes as the surface snow becomes wet. The forecasted afternoon cloud cover could dimish the chances of larger loose wet instabilities on slopes where the clouds provide shade. These clouds could also bounce some of the heat back onto other aspects and cause wet sticky snow to form on some more northerly aspects. Most of these loose wet instabilities should not entrain enough snow to bury a person, but they could knock a person over or push a person into terrain where collisions or a fall would have serious consequences. 

  • Wind Slabs

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

    Some wind slabs may still linger on near and above treeline N-NE-E aspects and cross-loaded SE and NW aspects. Complex or extreme terrain like unsupported slopes, cliffy areas, or steep exposed couloirs hold the best potential for unstable wind slabs, but some could also exist in the most heavily wind-loaded terrain. Avalanches resulting from the failure of these wind slabs could involve enough snow to bury or injure a person (size D2). In addition to these wind slabs, large fragile cornices also exist above many wind-loaded slopes.

    Use clues like wind drifted snow, cornices above slopes, wind pillows, and wind-sculpted snow surfaces to identify and avoid areas of potentially unstable wind slabs, and give cornices a wide berth since they often break well away from their edges.

  • Deep Persistent Slabs

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

    While they are unlikely in most of the forecast area since other persistent weak layers have become unreactive, isolated persistent slab avalanches may remain possible in the Carson Pass and Ebbetts Pass areas. If a persistent slab avalanche does occur, it could involve enough snow to bury or injure a person (size D2 with some potential for an isolated D3). A layer of loose weak snow near a crust 8 to 18 inches below the surface represents the persistent weak layer for this problem (near crust facets). Observations including snowpit tests and snowmobile triggered shooting cracks yesterday continue to indicate that this layer remains weak on some near and below treeline NW-N-NE facing slopes in the Carson Pass and Ebbetts Pass areas. Significant uncertainty still remains as to how widespread this problem may be.

    Look for and avoid avalanche terrain in any areas where snow surface cracking, snowpack collapse with a possible whumpfing sound, and/or unstable snowpit test results are occurring.

Avalanche Discussion

* Snowmobile cuts triggered shooting cracks on the buried persistent weak layer of near crust facets in the Ebbetts Pass area yesterday. 

* Snowpit tests targetting the near crust facet layer near Ebbetts Pass and some tests on Red Lake Peak (Carson Pass area) indicated that if the layer breaks fractures can still travel along that layer. 

* Most snowpit tests and observations in the Mt. Rose backcountry on Incline Lake Peak and Tamarack Peak and tests on Mt. Judah (Donner Pass area) indicated that the older weak layers have gained strength and that fracture propagation along the old layers has become unlikely. 

* Some skier triggered cracking occurred on wind-loaded test slopes on Mt. Judah (Donner Pass area). Large tender cornices also existed above most wind-loaded slopes.

* Minor E wind scouring had occurred in some areas on Red Lake Peak (Carson Pass area) and on Incline Lake Peak (Mt. Rose backcountry) but observers did not report any significant wind slabs on westerly aspects. 

* Observers reported small loose wet instabilities and wet sticky surface snow during the afternoon on Incline Lake Peak, Red Lake Peak, Mt. Judah, and in the Ebbetts Pass area.

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