Bollettino valanghe

Maritime

Valdez Avalanche Center
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Pericolo valanghe

Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
1 · Debole
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In sintesi

The avalanche hazard is CONSIDERABLE above 1500'.  The main concern today will be Wet Loose avalanches, which will be likely today below 3000' in steep terrain.  Above 3000' dense storm slabs continue to build that will also be likely to trigger up to 2' in depth.  Natural avalanches are possible.

The hazard is low below 1500'  in the Maritime zone due to minimal snow coverage and rain at low elevations.  Keep in mind that avalanches may be able to run into low elevations in defined avalanche paths.

Problemi valanghivi

  • Loose Wet

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

    Temperatures continue to rise with rain on snow below 3000' that is forecasted to continue through the day.   Rain is forecasted to occur all the way up to Thompson Pass at road level today.  The temperature at the road summit was 32° at 5am with .58" of liquid precipitation recorded at 12 mile in 24 hours.

     Expect to encounter wet loose activity below 3000' in terrain steeper than 35°, that could be human triggered or natural.  Roller balls or snow snails are a visual sign that wet loose conditions are present.  Pay attention to the terrain you are traveling on. What is above and below you?  The size of wet loose avalanches directly coorelates to the size of the slope above you.  The consequences correspond to what is below you, where will a wet slide potentially take you?  Is there a gully or terrain trap that could pile up deeply? Cliffs? Thin rocky areas?  The sensitivity relates directly with how saturated the surface of the snow is, this can be tested by putting your hand into the snow to feel how far down the wet or moist snow goes, and where the dry snow begins.  This problem is expected to increase through the day with continued rain on snow.

    Wet loose is only a real concern for the mid elevation band of the maritime zone due to lack of snow down low and snowfall occuring above the 3000' elevation mark.

  • Storm Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1.5–2.5

    Dense storm slabs continue to build in depth, with Nicks snotel measuring 15" of new snow in the last 48 hours.  This new snow has been deposited on a variety of old wind damaged surfaces.  An additional .5-1" of precipitable water is expected for our area in the next 24 hours, which will translate to 6-12" of additional snowfall above 3000'.  

    On 12/4, storm slabs were found to be ~12" in depth and upside down, with evidence of previous rain on snow below 3000'.  Bonding and stability were found to be fair to the old wind board, However, as snowfall continues through the day, stress will continue to be added to these upside down storm slabs, increasing the likelihood and depth of human triggered avalanches.  Pay attention to the depth of new snow, along with its sensitivity and how well it is bonded to old snow surfaces.  Sensitivity can be judged by watching for red flags such as shooting cracks, collapsing, and using small test slopes to jump or ride on to watch for failure.  Bonding can be assessed by employing simple hand shear tests to check for bonding at the new/old interface as well as looking for density changes within the new snow that could act as a failure plane.  These should be done in various areas since the underlying bed surface is currently extremely variable and bonding is likely to vary. 

     

Avalanche Discussion

Avalanche Activity last 72 hours:  Skies cleared mid day and revealed very little natural avalanche activity from the Port of Valdez through milepost 39.

D1.5 wet loose avalanche on a south aspect of Hogsback ridge at about 3000' running towards Robe lake.

D1.5 wet loose avalanche on a North aspect of North Oddessey at ~ 3400'.  

 D1.5 soft slab avalanche was observed on South aspect of South three pigs at MP 38 with crown filled in mid storm. Ran ~ 500'.

Our snowpack is undergoing a drastic change from wind damaged surfaces of every variety caused by brutal strong arctic winds to now being pressured by a warm and wet low pressure system originating from the Pacific Ocean.  This sort of drastic change will create an increase in the hazard level for any snowpack, but especially so for our thin early season snowpack.  Use caution during this period and give the snowpack time to adjust to these changes.   In addition to avalanche hazards, there are many other obstacles out there , including rocks that have just been shallowly covered, open water, and shallowly bridged crevasses.

The mid elevation snowpack continues to become rain saturated increasing the likelihood for wet loose avalanches to occur in steep terrain both natural and human triggered.  Storm slabs continue to build and be a concern above the freezing line that is wavering around 3000'.  It is a good time to be patient and avoid steep terrain or large avalanche paths as the snowpack is developing.

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