Lawinenlagebericht

Central Sierra Nevada

Sierra Avalanche Center
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Lawinengefahr

Fri
Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
2 · Mässig
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Kernpunkte

Isolated areas of weak snow below the recent storm snow could continue to exist in some sheltered near and below treeline locations.  Another warm day with sunny skies will cause snow to slide down steep sunny slopes.  Make a plan that focuses on the current conditions and utilize lower angle terrain if unstable snow is encountered. 

Lawinenprobleme

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    2–2.5

    Lingering instability could continue where a layer of buried surface hoar or near surface facets exists below our recent storm snow.  This is an isolated avalanche problem and highly variable where these layers exists and if they are still reactive.  Many recent observations have shown these layers to be unreactive, with the buried surface hoar being flattened, small in size, or not present.  Where this surface hoar is buried upright and is very large in size, greater than 10mm, are the most concerning areas.  Unfortunately, buried surface hoar can have uneven distribution through terrain and can also be highly variable in reactivity.  Unlike typical storm slab issues, these layers will take longer to adjust and fully gain strength.    

    Continue to look for signs of instability while traveling in the backcountry:  recent avalanche activity, shooting cracks, whumpfing, or collapsing would indicate an active weak layer in your area.  Remote triggering and wide propagation are also possible with persistent slab avalanche problems.  Utilize good terrain management strategies with your group to limit or avoid your exposure to this avalanche problem.  

  • Loose Wet

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–2

    Another day of warm temperatures and light winds will cause a wet loose avalanche problem to develop as daytime warming occurs.  Roller balls and pinwheels are expected with larger wet loose avalanches entraining more snow becoming possible.  Larger sun exposed slopes could have long running wet loose avalanches today.  Most sun exposed slopes are starting to develop surface crusts.  Once these melt and the snow surface becomes wet, heavy, and/or sticky-it’s time to move off of steep avalanche terrain or change aspects.

Avalanche Discussion

  • Numerous avalanches were reported and occurred on Sunday Feb 5 during or just after the recent storm.  No avalanches have been reported since this date.
  • Whumpfing, cracking, collapses, and unstable snowpack tests were reported on both Sunday and Monday.
  • The layer of surface hoar buried on Jan 29 varies widely by location in both crystal size and weakness.  Areas around I-80 and north seem to have the highest chance of larger surface hoar being buried and potentially still reactive.  These areas would include the Yuba Pass, Little Truckee Summit, Independence Lake, and potentially the Donner Summit areas.
  • Wet surface snow exists on E-SE-S-SW-W aspects up to at least 8500'.  Thin sun crusts are starting to form in these areas.

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