Avalanche forecast

Maritime

Valdez Avalanche Center
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Avalanche danger

Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Highlights

The avalanche hazard is Moderate above 1500 feet and low below.   Fresh wind slabs less than 1 foot in depth will be possible to trigger in specific areas.  Natural avalanches are unlikely.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–1.5

    There are currently two types of windslab out there in our forecast area.  The first are old hard slabs that were created 2/27-3/2 by a strong prolonged north wind event.  These have had a week of settlement time since their formation and have been reported and observed as unreactive to human triggers.  Slab depth and distribution are variable and knife hard.  Old wind slabs could be a concern where they are thinner and a person's weight can still penetrate them, or in the continental zone where they may overlie facets in isolated locations.

    The second type of wind slab we have is shallow (< 1 foot) but may be more sensitive to human triggers.  After a few days of mild weather, North winds kicked back up on the night of 3/7 to near 50 mph for a brief period on Thompson Pass.  Wind slab formation was limited in depth due to just 1-4 inches of snow that fell on 3/5 being available for transport.  Expect to find shallow wind slabs in specific locations such as the lee side of terrain features, high elevation ridge lines, and cross-loaded gullies.  Be on the lookout for these fresh wind slabs and use small test slopes to judge their sensitivity.  A couple of inches of new snow has fallen overnight which will add to the amount of snow available for transport.

Avalanche Discussion

We are entering a pattern shift towards light accumulating snowfall after the late February windstorm that caused widespread damage to the snowpack throughout our forecast area.  Strong winds have left us with a variety of scoured surfaces and knife-hard wind slabs. Several large  D2-D3 avalanches failed naturally during the windstorm and were triggered by intense wind loading. Windslabs created during this period have had almost a week to bond and stabilize and are unreactive.   The question moving forward will be how well will new snow bond to these old wind affected surfaces.  We currently don't have enough new snow to make a storm slab issue, although shallow fresh wind slabs are likely forming in specific locations.

Very hard snow surfaces exist that have created a strong bridging effect above the mid and lower snowpack.  This hard snow will confine instabilities to above the late February wind damaged snow for the near to mid term.  As time goes on and old wind affected surfaces become buried, their bridging effect will slowly decrease as they break down and lose strength with time.  Avalanches beneath this layer may occur later in the season but are unlikely at this time.

On 3/7 widespread surface hoar was observed from Thompson Pass and to the North from road level to above 3500ft. This may become a layer of concern in areas where it wasn't destroyed by the brief outflow the night of 3/7.

Glide cracks exist in isolated areas and will be a hazard throughout the season until they fail.  Avoid exposure to glide cracks.

Valdez season snowfall: 249  inches

Valdez March snowfall: 1 inches

Valdez height of snowpack: 69 inches

Thompson Pass season snowfall: 596 inches as of 3/1

46 mile height of snowpack: 72 inches

 

Regions covered