Valdez

Forecast Expired

Above 4,000ftConsiderable

2,000 to 4,000ftModerate

Below 2,000ftLow

Degrees of Avalanche Danger

Avalanche Problems

Problem 1

Wind Slab:

Likelihood:

  • Almost Certain
  • Very Likely
  • Likely
  • Possible
  • Unlikely

Size:

  • Historic
  • Very Large
  • Large
  • Small

Trend

  • Increasing
  • Steady
  • Decreasing

Problem 2

Glide Avalanches:

Likelihood:

  • Almost Certain
  • Very Likely
  • Likely
  • Possible
  • Unlikely

Size:

  • Historic
  • Very Large
  • Large
  • Small

Trend

  • Increasing
  • Steady
  • Decreasing

Problem 3

Persistent Slab:

Likelihood:

  • Almost Certain
  • Very Likely
  • Likely
  • Possible
  • Unlikely

Size:

  • Historic
  • Very Large
  • Large
  • Small

Trend

  • Increasing
  • Steady
  • Decreasing

Avalanche Activity

12/18- A large glide release was reported off Snowslide Gulch middle peak size 2.5.

12/15- Observed small natural avalanche on west aspect of Goodwills.   Released below a cliff band at the bottom of a slope, 100′ wide.   SS-N-D1-N

12/8-  An observer witnessed a glide crack avalanche.  SW aspect of peak 4690′ above the Valdez Glacier Lake. The debris reportedly ran all the way to the lake, with the deposition pile only feet away from a well used cross country ski trail.

Weather

12/22- Sunday is forecasted to have a clear morning before clouds and then precipitation begin to infiltrate our area. Winds are forecasted to abate, but will remain moderate at Thompson Pass out of the NE.

The Thompson Pass Mountain Forecast covers the mountains (above
1000 ft) surrounding Keystone Canyon through Thompson Pass to
Worthington Glacier.

This forecast is for use in snow safety activities and emergency
management.

                   Today        Tonight

Temp at 1000`      20 F         15 F

Temp at 3000`      11-17 F      15-24 F

Chance of precip   30%          100%

Precip amount
(above 1000 FT)    0.02 in      0.25 in

Snow amount
(above 1000 FT)    trace        3-5 in

Snow level         sea level    sea level

Wind 3000` ridges  E 3-25 mph   NE 8-30 mph
  24h snowfall (inches) HN24W (inches)* Hi Temp (F) Low Temp (F) Dec snowfall Season Snowfall
Valdez 0 0 18 14 7 31
46 mile Trace 0 2 -5

Nicks snotel

(4500′)

0 0 11 6

 HN24W= total water received last 24 hours in inches

Additional Information

Winds are beginning to fade on Thompson pass.  Human triggered avalanches are still likely today on wind loaded slopes steeper than 30°. Only expose one person to a slope at a time and avoid terrain traps.  Hazard is slowly decreasing.

With the first real cold snap of the season,  the snowpack will begin to lose strength at the surface and below.  Surface hoar up to 4 mm has been observed up to brushline on Thompson Pass.  Much of this will likely be knocked down by wind, but not in protected areas where it will continue to grow with falling temperatures.  Below 4,000′, we have two significant rain crusts in the top meter of the snowpack.  These layers, which are currently strong, will begin to lose strength as they form facets.  The amount of faceting will depend on the length of the cold snap.  This will be an important factor for subsequent snowfalls.

On 12/20, found reactive wind slab on test slopes in the Mt. Dimond area.  Wind slab was 6-18 inches deep and failed at the 12/9 rain crust. There is a lot of spatial variability with the 12/9 rain crust, as in some places it reaches only up to 3000′ and in others it is found up to 4500′. In this location, the rain crust was faceting and losing strength.  Above 4000′, where there is no rain crust, there is more available snow for transport which means deeper wind slab.  

The further north you go from Thompson Pass, expect thinner snowpacks.  Triggering an avalanche on a persistent weak layer will be more likely in the continental zone.

If you have traveled in the mountains, please leave a public observation.  The more info we can get from various locations will help us to get a clearer picture of the snowpack in our beautiful Valdez Chugach! 

Forecast Confidence is Moderate.

Video taken 12/20 in the Mt. Dimond area showing reactive test slopes.   https://vimeo.com/user106668057/review/380916811/02da5d1cc7

Announcements

The avalanche hazard is considerable at upper elevations.  Human triggered  avalanches are still likely on wind loaded terrain that is steeper than 30°. Good indicators for windslab are a rapid increase in depth of the new snow over a short distance, and a hollow, drum-like feel.  Shooting cracks will indicate unstable snow.  Use caution in the mountains today, avoid areas that are receiving active wind loading and avoid terrain traps.