Bollettino valanghe

Maritime

Valdez Avalanche Center
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Pericolo valanghe

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

In sintesi

The avalanche hazard is Considerable above 3000' and Moderate below.  Human triggered avalanches 1-2 feet in depth are likely at upper elevations where new storm totals are higher and wind has created deeper and more sensitive pockets of snow.  Below 3000' human triggered avalanches are possible up to 1 foot in depth as we are within 24 hours of 8-12 inches of new snowfall.  Wet loose activity will become possible on solar aspects if the sun comes out.

Problemi valanghivi

  • Storm Slabs

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

    Observations from 2/28 found that the most recent round of snowfall from Thursday-Friday is 8-12 inches deep on Thompson Pass.  This new snow overlies old wind slabs that formed on the 26th in specific areas.  An increase in temperatures yesterday caused the most recent snowfall to become upside down.  The amount of snowfall received with less than 24 hours of settling time and top heavy characteristic of the new snow will make human triggered avalanches likely at upper elevations where snowfall totals are the highest and higher wind speeds have likely created deeper and more sensitive pockets of new snow.   Instabilities within the new snow are not expected to persist, but we are within 24 hours of a moderate amount of snowfall accumulation.  There is uncertainty in the stability of the most recent snowfall due to multiple recent changes in weather.  

    As stated above this new snow overlies old wind slabs at upper elevations and near wind channeled terrain.  These old wind slabs were found to be stubborn-unreactive yesterday.  However, instabilities may linger and visually identifying these old slabs is no longer possible due to the new snow we have received.  

    Use small test slopes without consequence and hand shear tests to gather information about the depth of new snow and how well it has bonded.  Anticipate what slopes would have been loaded by North wind on the 26th.  Avoiding these areas will limit the amount of potential instabilities you have to deal with.

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1.5–2

    There are currently 2 persistent weak layers on our radar, a layer of buried surface hoar from Valentine's Day as well as weak snow below a decomposing rain crust from late January. The extent of both layers is limited to lower elevations. Below 1500 feet a rain crust is buried 12-16 inches, and has shown reactivity in recent observations. Collapsing and propagation in ECTS from multiple locations has been taking place on this layer within the last few days. Currently, we have not seen any avalanche activity on this layer but that is becoming increasingly possible with continuing snow/rain loads as well as further weakening of the old rain crust. 

    Buried surface hoar from 2/14 exists in wind protected areas from 1500 -2500 feet.  Burial depth in the maritime zone is around 2 feet and a bit shallower moving inland. This layer showed reactivity in pit tests earlier this week with clean shears in ECT tests. So far we are not seeing propagation or avalanche activity on this layer but that may change with continued stress.  

    To limit exposure to both of these layers avoid terrain traps and  consider using conservative terrain while moving through low elevations..  There is uncertainty on the current and future reactivity of these two layers. We are keeping these on our list, as current weather conditions will continue to stress these layers. 

     

    (2/28/2025)

    Failure of the buried surface hoar on  a shear planar surface in pits tests. 

    Photo: Joshua McDonald

  • Loose Wet

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

    Above-freezing temperatures with moderate to heavy rain mixed with wet snow have been occurring from sea level to 1500 feet over the last  24 hours, creating the possibility for wet loose avalanches. The surface snow has already encountered above freezing temperatures which will dull the reaction the surface snow has today.  A period of sunshine is possible today that will increase the likelihood of wet loose avalanches on solar aspects especially above the freezing line where new snow exists that will be succeptible to solar input.

    When assessing wet loose hazards, it is essential to take the hazard in relation to the terrain you are exposing yourself to.  Are there terrain traps? Are there consequences if I were to be swept off my feet by even a small avalanche? 

    The size and shape of the terrain above you along with the amount of loose snow available to slide, directly correlates to the size of the wet loose activity that can occur. Terrain traps and exposure below you compound consequences.

     

Avalanche Discussion

Observed Avalanche Activity last 72 hours: 

Dry loose D1-2 natural activity releasing from steep terrain in the Port of Valdez and Thompson Pass.  Small to moderate wet loose activity in steep low elevation terrain.

Forecast Discussion:

Consistent rounds of incremental snowfall have been gradually building the amount of loose snow above a layer of hard wind affected snow above 3000' that formed in early February.  Good bonding has been continously observed at this interface at multiple locations.  This gradual building of storm slab depth was disrupted on the 26th as a brief North wind event redistributed new snow at upper elevations and locations close to Thompson Pass.  This has created a decent amount of spatial variability as potential instabilities are expected to exist at the interface of the most recent snowfall as well as weaknesses that may be lingering in older wind slabs that are now masked by new snow.  As stated above, these instabilities are not expected to persist. However, uncertainty exists with the multiple changes in recent weather.  A considerable rating has been applied to upper elevations due to this uncertainty as well as limited settlement time within the new snow.

Persistent weak layers have shown signs of instability in specific low-mid elevation terrain. These layers have not yet produced avalanches but the likelihood of doing so is increasing. This is not a widespread problem but could take a traveler by surprise in isolated steep, low-elevation terrain. Use caution when traveling up or down through areas that may have persistent weak layers. Uncertainty exists on the current and future reactivity of these layers so we will be keeping a close watch and posting updates when we get more information. 

 

 

Additional Information:

Active rockfall has been recently reported in Keystone Canyon.

A weather and snowpack season history is available by clicking on the Season Summary tab which is located below the bottom line statement once you have entered the full forecast.

Season Snowfall Data

Location 24 hour Snowfall Inches- 3/1 24 hour Snow Water Equivalent Inches Height of Snow February Snowfall Inches Season Total Snowfall Valdez   Trace    .2    50     10      Thompson Pass    N/O    N/O   N/O    N/O    ~500 Nicks    3    N/O    138    ~18 N/O 46 Mile    Trace     0   22    ~4 N/O

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