Avalanche forecast

Continental

Valdez Avalanche Center
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Avalanche danger

Alpine
3 · Considerable
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

The avalanche hazard will begin as Moderate and move to Considerable during the day at upper elevations.  Strong south winds and heavy snowfall will build storm slabs that will be likely for a person or machine to trigger once new snowfall amounts exceed 6 inches.  The majority of accumulation is expected to begin this evening, if heavy snowfall arrives sooner than forecasted the hazard will move to Considerable at all elevations.

 

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2

    A strong winter storm has begun to affect our forecast area with 12-18 inches of new snow expected above 2000' by mid day Monday.  High elevation zones that are typically favored for heavy snowfall may see up to 3 feet of new snow.  The majority of accumulation is expected to begin around 4 pm today and continue through the evening.  Expect for the hazard to begin the day as Moderate as only shallow storm slabs exist.  Snowfall rates are expected to reach 1"/hour by this evening at upper elevations, at that point the hazard will quickly rise to Considerable.  The freezing line is forecasted to rise to 1700' briefly this evening with rain at low elevations becoming possible.  Cold air is then forecasted to filter in overnight and return snow lines to sea level.

    Heavy new snowfall is falling on surface hoar above 3000' that formed on the night of 3/27.  This type of snow grain is notorious for acting as a weak layer and has the potential to be very sensitive and prolong instability much longer than a typical storm slab.  Surface hoar has been reported and observed to be widespread above 3000'.   Once more than 6 inches of snowfall has accumulated expect for human triggered avalanches to become likely.  Initially their depth will equal new snowfall amounts, however if new snow amounts exceed 2 feet it will become possible to see the 3/9 buried surface hoar layer reactivate and produce very large avalanches in the Continental zone on north aspects.  In addition to heavy snow, winds from the south are expected to become strong which will build deeper slabs on lee slopes that will be even more sensitive to human triggers.

    Today it will be important to pay attention to new snowfall amounts.  The hazard will directly coorelate with new snowfall amounts.  Shooting cracks, collapsing and recent avalanche activity are all signs that unstable snow exists.

     

    (3/28/2024)

    2-6 mm Surafce Hoar on ridgetops in The Books ~5400'.

    Photo: Gareth Brown

Avalanche Discussion

RECENT AVALANCHE ACTIVITY:  

No natural or human triggered avalanche activity was reported or observed in the last 24 hours.

The previous 48 hours saw some wet loose activity on solar aspects.

DISCUSSION:

Significant snowfall is expected over the next 36 hours.  Upper snowpack stability will rapidly change this afternoon from stable to unstable as heavy snowfall arrives.  New snow will be accompanied by strong southerly winds with gusts in the 70's possible at upper elevations overnight.  Deep storm slabs that form will be deposited on a layer of surface hoar that formed during the clear and calm weather at the end of last week.  This layer will exist on the northern half of the compass above 3000'.  

Easterly winds were on the increase yesterday which may have destroyed surface hoar in some locations.  There is considerable uncertainty regarding the extent to which yesterday's wind affected the surface hoar.

Additional Concerns:

Rain on snow may happen below 1500' this afternoon and create the potential for wet loose activity to occur.  This problem is expected to be short lived as colder air is forecasted to return overnight and drive the freezing level back to sea level.

This is the time of year when cornices begin to fail.  You can significantly reduce your overall exposure in the mountains this time of year by avoiding traveling on top of or under cornices.

A very significant Glide avalanche/ landslide in Upper Stuart Creek last week is a great reminder of the destructive forces involved with glide crack failure.  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: 269  inches

Valdez March snowfall: 20 inches

Valdez height of snowpack: 70 inches

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

46 mile height of snowpack: 68 inches

 

Regions covered