Bollettino valanghe

Bridgeport Avalanche Center

Bridgeport Avalanche Center
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Pericolo valanghe

Sat
Alta quota
4 · Forte
Limite del bosco
4 · Forte
Sotto il limite
3 · Marcato
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In sintesi

Fluctuating temperatures, gale force winds and heavily increased precipitation overnight, has made for dangerous avalanche conditions today.  Human triggered avalanches are very likely. Travel in, near, or below avalanche terrain is not recommended

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Very Likely
    Dimensione
    1–2.5

    Gale force winds yesterday and overnight from the S-SW combined with heavy new snow and rain, will make thick wind slabs on leeward slopes our main concern. This combined with new snow and warming temps will increase a heavy/over light upside down snowpack even more of a concern.  Look for above tree line leeward slope slab development, a widespread and reactive problem today.  Stay out of avalanche terrain, especially with larger slopes above you and consequential terrain traps below. Wind speeds over the Sierra front over the past 24 hours have been in the average of 50-60 mph with gusts up to 140 mph yesterday.  Wind can easily transport 3-5x the amount of snow onto leeward slopes and protected convexities, making for large wind slabs. This snow may sound hollow or look pillowed on the terrain or you may not even notice it until it breaks.

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1.5–3

    Our high and dry January surface facet layer is now buried 2-3 feet deep in specific, shaded and protected spots between 8500'-1100' elevation, with a thick heavy slab of wind packed snow and denser rain/snow on top of it.  This suspect weak layer will be harder to trigger but will be much a larger and consequential avalanche when it does.  The much easier to trigger wind slab on top, could easily step down to this deeper and more destructive instability.  This avalanche will propegate from rock to rock feature in the snow pack and be very large if triggered. 

    Photo: Late Dec 24' of soft weaker layer at the base of snow pack that may come into play with heavier layers on top of it.

Avalanche Discussion

  • There is a good chance that there was a large WET snow avalanche cycle overnight-last night,  with up to 3.5 Inches of SWE in the past 24 hours, means it is very heavy and condensed. Combined that with temperatures rising yesterday evening to above freezing levels in much of the terrain. New snow with rain on top and more heavily wind driven snow on top of that, has created a dangerous sandwich of layers. Much of this sitting on top of weaker snow bed surface underneath. Zones that didn't avalanche last night, are primed and ready for a trigger today.  Give the higher angle slopes time to settle today, as the weekend looks beautiful and avalanche concern will lower as time passes.
  • The VARIED surfaces of the January snow pack are continuing to come into play now. As those varied surfaces are now buried. Surface facets, buried surface hoar, melt/freeze sun crust, wind pack snow are all behaving and bonding differently making for a checkerboard of subsurface instability. 
  • Much of the South (solar) facing snow pack is shallow if it exists at all.  Look for rocks underneath the surface and walk softly in these aspects as there isn't much snow there to support ya.. AKA the sharks are out! 
  • Not all of our terrain north to south received the same amounts of precip.

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