Bollettino valanghe

Maritime

Valdez Avalanche Center
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In sintesi

The Avalanche hazard is CONSIDERABLE at all elevations.  Heavy snowfall at upper elevations and heavy rain at lower elevations has elevated the avalanche hazard.  Human triggered avalanches are likely up to 4 feet in depth above 2500 feet and wet loose avalanches are likely where rain on snow is occurring.  Natural avalanches will be possible today.

Problemi valanghivi

  • Storm Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    2–3

    The last 3 days of wet weather has brought nearly continoious precipitation especially for coastal areas.  What began as snow for all elevations and 6-12 inches of accumulation depending on location turned to rain the night of the 5th below 2000'.  Since then heavy rainfall has been occurring below 2000' with heavy snowfall above.  Temperatures peaked the night of the 6th along with strong southerly winds.  Freezing line may have risen to 4000' for a period.  Precipitation is expected to lighten today, although it continues with light winds, and the freezing line descending to 1000'.  This will allow the snowpack to drop from a HIGH avalanche danger to Considerable, however the overall snowpack remains under considerable stress.

    Above 2000' Human triggered storm slabs will be likely to trigger.  The depth of these will increase with elevation as areas in the 2000-3000' elevation band received rain mid way through the storm, limiting storm total amounts.  Deep storm slabs exist above 3000' that will be reactive to human triggers, strong winds the night of the 6th will have created even deeper pockets in specific areas.  Conservative terrain choices and cautious route finding will be necessary for safe travel in avalanche terrain today.

    Storm slabs will be putting pressure on various persistent weak layers that exist in the mid snowpack.  Step down avalanches are possible today especially in the Continental zone.

  • Loose Wet

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

    Rain on snow over the last 48 hours has created a high likelihood for wet loose avalanches to occur naturally and be human triggered.  The peak natural activity has already passed along with peak temperatures and rainfall intensity.  However, dangerous conditions remain.  The potential danger of wet loose avalanches is directly correlated with the vertical fall and steepness of the slope in question.  The larger the slope, the more entrainment that can occur.  Terrain traps will significantly increase the consequences of wet loose avalanches as even small slides can pile up deep debris.

    It is recommended to avoid traveling on or below terrain steeper than 30° where the surface of the snow is unfrozen. 

Avalanche Discussion

Observed Avalanche Activity last 72 hours: 

Natural D2+ D3 avalanche debris has been observed on South Three Pigs and Mt Tiekel.  There is likely more activity, however cloud cover has prevented natural activity observation.

Forecast Discussion:

The situation is rather simple.  We have received 4 feet or more of snow above 3000' since the 4th.  This amount of snow puts significant stress upon the snowpack.  Untill precipitation stops and snowpack is allowed time to accept this new weight, Human triggered avalanches will be likely.  Precipitation is expected to lighten up today but will be on the increase once again tonight and likely through the weekend.  If you decide to travel in avalanche terrain today use cautious route finding, avoid terrain traps, maintain good group communication and only expose one person to a slope that is steeper than 30° at a time.  Signs of instability such as shooting cracks, collapsing or recent natural avalanche activity are all direct indicators to travel on slopes less than 30°.

It is not just the amount of new snow that is a concern.  But there are also potential persistent weak layers in our snowpack, creating not just a higher likelihood for avalanches to initiate but also leading to the possibility of step-down avalanches that would be much larger and more destructive.

Storm totals are unclear currently, but this is the information we have:

Valdez: 2.77" storm total water (mostly rain)

12 mile: 3.22" storm total water (mostly rain)

Thompson Pass: 44" snow  estimated 

Nicks Snotel: 28" snow (strong winds have likely redistributed snow from this site)

Additional Information:

Continue to avoid Glide cracks in the area where they exist from Nick's Buttress through Cracked Ice at mid elevation.  Some of these are being filled in by snow and no recent activity has been noted

If you travel in the Continental zone today, exercise extra caution as there is very limited field data from this location.  It is unclear as to whether deep slab instabilities exist, however propagation at the ground on an ECT was observed in a snow pit as recently as 1/2.

If you get out in the mountains today consider leaving an observation to help increase the understanding of current snowpack stability.  

A weather and snowpack season history is available by clicking on the Weather History tab that is located above the bottom line statement once you have entered the full forecast.

Season Snowfall Data

Location 24 hour Snowfall Inches- 1/8 24 hour Snow Water Equivalent Inches Height of Snow January Snowfall Season Total Snowfall Valdez     0    N/O    17     10     45 Thompson Pass    15    N/O   N/O    52    N/O Nicks    wind affected    N/O    71    31 N/O 46 Mile    0     N/O   24    6 N/O

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