Bollettino valanghe

Central Sierra Nevada

Sierra Avalanche Center
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Pericolo valanghe

Fri
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
2 · Moderato
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In sintesi

Changing wind directions and blowing snow will continue to make wind slab avalanches possible today.  Sunny skies could also cause some wet snow instabilities on slopes with direct sun exposure.  Use caution in areas with recent blowing snow and on steep sunny slopes as daytime warming occurs.

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–2

    Changing wind directions over the last couple days have drifted snow in many areas.  Large touchy cornices and wind slabs were formed yesterday by the NE winds which switched early this morning to the W and will continue through today in the moderate to strong range.  With plenty of light new snow still available for wind transport, wind slabs will be possible on all aspects in near and above treeline areas today.  These wind slabs could be forming or formed next to other areas that are being scoured by the changing winds.  

    Look for blowing snow, drifted snow, and any snow surface clues that can help inform your group where wind slabs have formed or are forming.  Cracking around skis while traveling through wind drifted areas would indicate cohesion in the wind slab.  Make travel plans around steep wind loaded terrain and areas below large cornices.

    (2/23/2022)

    Cornices collapsed on approach with fairly wide propagation given the size of the terrain.  Hidden Peak, West Shore area.

    Photo: Steve Reynaud

  • Loose Wet

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–2

    This will be the first full day of intense late February sun after our recent storm.  Solar radiation today will warm the snow surface and cause wet snow to form on E-SE-S-SW-W aspects as daytime warming occurs.  Areas that intensify the solar radiation, around rocks and gully features, will be the first locations to show rapid warming and wet snow development.  Most wet loose instabilities are expected to be in the mid to lower elevation range, with higher elevations remaining cold with increased winds.

    Roller balls and pinwheels will occur today as wet snow develops.  Larger wet loose avalanches could also become possible today and into the weekend as temperatures warm and winds decrease.  Some of these wet loose avalanches could involve most or all of the recent storm snow we received this week.  

Avalanche Discussion

  • Near-surface faceting during the long dry spell created weak snow in the top portion of the snowpack on some wind sheltered NW-N-NE aspects. Recent snow has buried this weak layer under 1 to 1.5 feet of storm snow.  No avalanches have been reported on this weak layer at this point, but some snowpack tests still show unstable results.  On a regional scale, this near surface facet weak layer is isolated in distribution with avalanches unlikely.  With that said, it would not be impossible for an isolated avalanche to occur on this weak layer in an area with all the right ingredients. 
  • Variable snow surface conditions ranging from firm ice to soft snow still exist under the storm snow. While the storm snow should help smooth out the snow surfaces, it may not be enough to fully insulate backcountry travelers from the old snow surfaces, especially in steeper terrain. 
  • Snowmelt has sped up since the beginning of February. Many more obstacles (rocks, bushes, etc) and areas of bare ground have melted out on SE-S-SW aspects.

Regioni coperte