Valdez

Forecast Expired - 02/24/2023

Above 3,000ftModerate

1,500 to 3,000ftModerate

Below 1,500ftModerate

Degrees of Avalanche Danger

Avalanche Problems

Problem 1

Falling Cornice:

Falling cornices have been reported in multiple locations on 2/22 that failed within the last 48 hours.  These have produced D3  (very large) avalanches in multiple locations including The Books.  Cornices have been observed and reported as being larger than normal and poorly attached.  Cracks on ridge tops showing cornices separating from ridge lines have been observed.  

 

Cornices are an objective mountain hazard that should always be a concern.  Although, recent activity strongly shows that we need to keep an extra cautious approach to avoiding overhead exposure to cornices.  Avoid traveling below or on top of cornices.  The avalanches that cornice fall has recently produced are unsurvivable events.

 

Likelihood:

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

Size:

  • Historic
  • Very Large
  • Large
  • Small

Trend

  • Increasing
  • Steady
  • Decreasing

Problem 2

Wind Slab:

North winds ramped up on 2/20 with gusts to 50 mph along ridge tops.  Wind slabs were found to be initially sensitive up to 1 foot in depth on SE-NW aspects.  On 2/22 slabs were found to be gaining strength and stubborn to triggers. Signs of instability were observed and reported in isolated areas.

 

In many places these slabs were deposited on very low density snow, making slabs quite sensitive initially.  This interface has been compressed since and sensitivity has decreased, although this problem may remain reactive in specific locations today up to 1 foot in depth.  As slabs settle and gain strength the likelihood of triggering one of these decreases, but propagations could be wider due to the stiffness of the slab.  Failure could occur once a person or machine is already on slope and initiate behind you.  This problem will currently have a hollow drum like feel, shooting cracks will be a sign that avalanches remain possible.

 

Areas where the surface is unaffected by wind will provide better riding conditions and good stability.

Likelihood:

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

Size:

  • Historic
  • Very Large
  • Large
  • Small

Trend

  • Increasing
  • Steady
  • Decreasing

Problem 3

Persistent Slab:

Natural avalanche activity caused by cornice fall reported on 2/22 indicates that a persistent weak layer in the mid snowpack exists at upper elevations. The 1/14 buried surface hoar layer is likely the weak layer involved, although this has not been confirmed.  This layer has been dormant for over three weeks, but recent activity shows that large triggers can still produce avalanches.  Human triggered avalanches remain unlikely at this layer although large groups, cornice/ice fall, or large groups may be able to still produce avalanches at this layer

 

Rain crusts that formed in late January have promoted faceting in the mid snowpack at low elevations (below 2500′).  No natural or human triggered avalanches have been reported or observed that failed at this layer, although poor structure exists and stability tests have produced propagation at this interface.  

 

As time goes on and this layer becomes deeper in the snowpack with additional snowfall, the likelihood of human triggers will be decreasing.  It is still worth investigating this layer if traveling in steep/ consequential terrain at low elevations.  Areas where the snowpack is thin will be the most susceptible to failures at this plane.

Likelihood:

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

Size:

  • Historic
  • Very Large
  • Large
  • Small

Trend

  • Increasing
  • Steady
  • Decreasing

Problem 4

Deep Slab:

Weak snow created by early season cold temps, dry conditions and strong north winds have showed poor structure near the base of the snowpack.  This weak snow has been dormant through the majority of the season with human triggered avalanches being unlikely at this layer.  As the sun has come out the last few days several very large natural avalanches have occurred with cornice and ice falls being the triggers.  Human triggers remain unlikely at this layer, although these events show that large triggers can affect this weak snow.  Cornice fall will be the most likely trigger to affect this weak snow, although it is possible that a large group could have the same affect.  Avoid overhead exposure to cornices.

 

In most location facets near the ground have been found to be rounding and unreactive in stability tests.  In thin areas of the snowpack basal facets have been found to be more developed.  If you find it is possible to push a ski pole to the ground in areas you travel, assume that a weak faceted snowpack exists in that location. These areas could act as a trigger point.  An example of the difference in faceted snow that has been recently found can be seen below.

 

Depth hoar from Nicks Buttress ~4000′ North aspect 1/31. This was from an area where the snowpack 3 feet deep.

 

Rounding depth hoar on Cracked Ice / north aspect/ 3000′  on 2/11.  This was from an area where the snowpack was 7 feet deep

Likelihood:

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

Size:

  • Historic
  • Very Large
  • Large
  • Small

Trend

  • Increasing
  • Steady
  • Decreasing

Avalanche Activity

Below is a summary of observed Avalanche activity from the last 7 days.  Avalanches that were noted earlier in the season can be viewed by clicking the link below.

If you trigger or observe an avalanche consider leaving a  public observation.

Valdez Avalanche Activity

2/22- Natural D 2.5 cornice fall avalanche was reported on a NW aspect/ ~6000 in the books.

 

2/20- Numerous D1-D2 natural and human triggered avalanches were observed and reported up to 1 foot in depth on a variety of aspects.  These occurred in areas where fresh wind slabs were present.

– D3 natural avalanche observed on Snoopys (Port of Valdez). NW aspect/ ~5000’/ ran ~3500 vertical feet with a track length of approximately 1 mile mapped on Google Earth.  This was a hard slab avalanche the failed at weak layer in the mid snowpack. HS-N-R4 D3.  No other avalanches of this size have been observed or reported in our forecast area.

 

2/15- The sun came out in full force after 6 inches of new snow and produced a significant amount of point release wet/loose activity near the coast on solar aspects.  2- D2’s were also noted in the mid and high  elevation band of town mountain and Mile high.

 

Weather

Check out our updated weather tab!  A collection of local weather stations are available for viewing with graphs and tabular data included.

NWS Watches and warnings

NONE
NWS Point forecast for Thompson Pass
Today
Snow. High near 26. Southwest wind 5 to 10 mph, with gusts as high as 20 mph. Chance of precipitation is 80%. Total daytime snow accumulation of 1 to 3 inches possible.
Tonight
Snow. Low around 19. Southeast wind around 5 mph. Chance of precipitation is 90%. New snow accumulation of 1 to 2 inches possible.
Friday
Snow likely before 3pm, then snow showers likely after 3pm. Cloudy, with a high near 25. Southwest wind around 5 mph becoming northwest in the afternoon. Chance of precipitation is 70%. New snow accumulation of around an inch possible.
Friday Night
Scattered snow showers before midnight. Mostly cloudy, with a low around 8. North wind 10 to 15 mph increasing to 20 to 25 mph after midnight. Winds could gust as high as 30 mph. Chance of precipitation is 50%.
Saturday
Partly sunny, with a high near 17. North wind around 25 mph, with gusts as high as 30 mph.
Saturday Night
Mostly cloudy, with a low around 3. North wind 20 to 25 mph decreasing to 10 to 15 mph after midnight.
Detailed forecast for Thompson Pass Mid elevation (2000-4000 Feet)
Date                           Thursday 02/23/23       Friday 02/24/23
Time (LT)          18    00    06    12    18    00    06    12    18
Cloud Cover        OV    OV    OV    OV    OV    OV    OV    OV    OV
Cloud Cover (%)    80    95   100   100   100   100   100    95    95
Temperature        17    13    14    22    24    21    19    22    21
Min/Max Temp                   12          26          19          23
Wind Dir           NE    SW     S     S     S    SE     W     W     N
Wind (mph)          2     4     8    10     6     3     4     5     8
Wind Gust (mph)                21    23                              
Precip Prob (%)    10    50    90    90    90    80    80    70    70
Precip Type               S     S     S     S     S     S     S     S
12 Hour QPF                  0.03        0.16        0.12        0.13
12 Hour Snow                  0.2         2.3         1.6         1.9
Snow Level (kft)  0.0   0.0   0.0   0.0   0.1   0.0   0.0   0.1   0.0

 Click on link below for Thompson Pass weather history graph:

https://docs.google.com/spreadsheets/d/e/2PACX-1vR_Fl5087NrNCo2BtsSaum-gxrx1QioHSO4YqEmjW76LhuDu9ZsSxbBCTl6zkYIFarys-5eM_7P5GpV/pubhtml

 

 

 

Date:

02/23

24 hr snow HN24W* High temp Low temp 72 hour SWE* February snowfall Seasonal snowfall Snowpack Depth
Valdez 0 0 29 11 0 69 214 63
Thompson pass  0 0 N/O N/O 0 69 356 67
46 mile 0 0 26 2 0 ~16 ~85** 42

 

 

*HN24W- 24 hour Snow water equivalent in inches

*SWESnow water equivalent

**46 mile seasonal snowfall total begins December 1st.

Additional Information

 

Click on the link below for a running summary of the seasons weather history.

Valdez Weather History

Announcements

The avalanche hazard is moderate at all elevations. Triggering a wind slab avalanche remains possible in isolated locations up to 1 foot in depth.  Shooting cracks, collapsing and recent avalanche activity are all signs of unstable snow.  Light snowfall today is not expected to be enough to affect stability.  Multiple large-very large natural avalanches have been reported over the last 48 hours that have resulted from cornice and ice falls.  Cornices should always be a hazard that we watch out for, although they appear to be particularly weak at this point.  Avoid exposure to cornices as they have shown the ability to produce very large unsurvivable avalanches.

 

Posted by Gareth Brown 02/23  8:45 am.

 

For a description of current avalanche problems, weather information, season history and more click the (+ full forecast) button.  Avalanche forecasts will be issued Wednesday-Sunday.

If you have pictures of recent natural or human triggered avalanches or notice signs of instability such as shooting cracks or collapsing, leave an observation to help improve forecast accuracy.