Bollettino valanghe

Central Sierra Nevada

Sierra Avalanche Center
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Pericolo valanghe

Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
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Non aggiornato — questo bollettino è scaduto 8 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

CONSIDERABLE avalanche danger exists today in near treeline and above treeline areas due to a wind slab avalanche problem. MODERATE avalanche danger exists below treeline due to possible storm slabs. Please note that this advisory is valid for 12 hours. The next update to this advisory will occur at 7 pm this evening. Increasing avalanche danger is expected tonight.

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1

    Blowing and drifting snow has been occurring for over 24 hours now with additional new snowfall added last night. Newly formed wind slabs exist near treeline and above treeline. These wind slabs are becoming larger in size and more widespread. The vast majority of wind slabs will be encountered on NW-N-NE-E-SE aspects. Isolated wind slabs may also exist in other areas where wind drifted snow is depositing, including below treeline. Wind slab avalanches large enough to bury or injure a person are likely today (size D2).

    Identify and avoid specific areas where wind drifted snow is depositing to form wind slabs. Ridgetop areas below cornice features and wind pillows will certainly hold wind slabs today. Snow surface cracking is also a sign of unstable snow.  Move around these areas with a wide margin for error and seek wind sheltered terrain in order to reduce avalanche hazard.

  • Loose Dry

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1

    New snowfall last night and additional snowfall today creates the possibility of storm slab avalanches. This avalanche problem forms in wind protected areas and is possible today near treeline and below treeline on all aspects. Open areas on NW-N-NE aspects where isolated patches of surface hoar were buried under last night's snowfall could have greater sensitivity to triggering. Storm slab avalanches up to size D2 are possible today, especially where new snow amounts approach 1 foot or more.

    Continually assess for signs of instability in below treeline avalanche terrain including snow surface cracking and recent avalanche activity. If signs of instability are encountered, be conservative with terrain choices and slope angles. Create wide margins for error.

Avalanche Discussion

* SSW ridgetop winds began moving and drifting snow near and above treeline yesterday before the start of new snowfall. Reports of blowing snow were received from parties in the Luther Pass, Desolation Wilderness, and Donner Summit areas.

* Two unintentionally skier triggered wind slab avalanches were reported yesterday in near treeline and above treeline terrain on NE-E aspects that traditionally receive efficient wind loading. The avalanches occurred on Mt. Tallac's Corkscrew Bowl (Desolation Wilderness area) and on Mt. Judah's East Face (Donner Summit area).

* No signs of instability were reported yesterday from below treeline areas. This was prior to last night's snowfall.

* A few isolated patches of surface hoar were noted pre-storm in wind protected open areas below treeline yesterday on Trimmer Peak (Luther Pass area).

* The mid level and deeper portions of the snowpack remain well consolidated and without problematic weak layers.

Regioni coperte