Forecast Expired - 12/09/2021

Above 4,000ftConsiderable

2,000 to 4,000ftConsiderable

Below 2,000ftConsiderable

Degrees of Avalanche Danger

Avalanche Problems

Problem 1

Persistent Slab:

The 12/5-12/6 storm that deposited 2 feet of snow in Valdez and 12-16″ on Thompson Pass has increased the depth of the slab that is sitting on the November facets.  Northeast winds have kicked up the morning of 12/8 which will add more stress and increase the likelihood of human triggered avalanches in wind channeled terrain.


There are many things that are unclear about our snowpack at the current moment.  What is clear is that we have a persistent slab avalanche problem.  What is unclear is how sensitive this layer is to human triggers at the present moment.  With red flags present as recently as 12/7, like large collapses and shooting cracks it is safe to assume that slopes steeper than 32° are reactive to human triggers. Stability tests have also showed propagation 2 feet deep in the pack.  Currently it would be wise to maintain a caution approach and avoid terrain with consequences.


The 24 hour rule will not apply for our current setup.  The only successful mitigation practices for a persistent slab avalanche problem are patience, and a conservative approach in choosing terrain.  Good protocols are very important as well during this type of avalanche problem ie: only exposing one person at a time to an avalanche prone slope, good communication and having an escape route should a slope fail.


Some important things to remember about a persistent weak layer problem is that tracks are not a sign of stability.  A slope can fail after many tracks have been laid down.  Also it will be possible to trigger avalanches remotely meaning a slope that is above you or adjacent to your position. 


Photo of 1cm+ chained facet found buried 40 cms (16″) on Catchers Mitt 3500′ SE aspect.




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


  • Historic
  • Very Large
  • Large
  • Small


  • Increasing
  • Steady
  • Decreasing

Problem 2

Wind Slab:

Northeast winds have kicked up to gusts in the high 30’s at Thompson Pass.  Expect to find fresh wind slabs up to 2 feet in depth in wind channeled terrain that will be reactive to human triggers.  Wind slab avalanches will have the potential to step down into deeper faceted layers in our snowpack (see problem 1) and produce larger avalanches.  Avoid recently wind loaded slopes in terrain steeper than 32°.







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


  • Historic
  • Very Large
  • Large
  • Small


  • Increasing
  • Steady
  • Decreasing

Avalanche Activity

12/7- Only a few natural avalanches were noted during the last storm.  It is likely there were more during the storm, but crowns may have been filled in by subsequent wind and snow.

D2 on Town mountain was observed ~3000′

A couple of D2’s were noted in N. Oddessey gully and Big Oddessey.

D2 on 40.5 mile peak ~5500′.

12/2-12/3- Several natural D2 avalanches were noted on south aspects of Three pigs, Hippie Ridge and Averys.  These windslab avalanches originated between 4000-5500 feet elevation.


NWS Watches and Warnings


Point forecast for Thompson Pass


Areas of blowing snow before noon. Mostly cloudy, then gradually becoming sunny, with a temperature falling to around 10 by 5pm. Northeast wind 25 to 30 mph decreasing to 15 to 20 mph in the afternoon. Winds could gust as high as 40 mph.
Partly cloudy, with a low around -3. Northeast wind around 15 mph, with gusts as high as 25 mph.
Snow, mainly after 9am. Areas of blowing snow before 9am, then areas of blowing snow after 3pm. High near 17. Northeast wind 15 to 25 mph, with gusts as high as 35 mph. Chance of precipitation is 80%. New snow accumulation of around an inch possible.
Thursday Night
Snow. Areas of blowing snow before midnight. Low around 14. Northeast wind 20 to 30 mph decreasing to 10 to 20 mph after midnight. Winds could gust as high as 40 mph. Chance of precipitation is 100%.
Snow showers likely. Cloudy, with a high near 18. East wind 5 to 10 mph. Chance of precipitation is 70%.
Friday Night
Scattered snow showers before midnight. Mostly cloudy, with a low around 3. East wind 5 to 10 mph becoming north after midnight. Chance of precipitation is 50%.


 Detailed forecast for Thompson Pass (mid elevation 2000-4000′)

DATE             WEDNESDAY 12/08         THURSDAY 12/09          
TIME (LT)        06    12    18    00    06    12    18    00    06
CLOUD COVER      BK    FW    SC    SC    SC    OV    OV    OV    OV
CLOUD COVER (%)  65    10    35    35    40    95   100    95    90
TEMPERATURE      19    14     5     1     3    16    16    15    18
MAX/MIN TEMP                 19          -1          18          14
WIND DIR         NE    NE    NE    NE     E     E     E    SE     E
WIND (MPH)       16     8     6     8     8    17    28    13    11
WIND GUST (MPH)  40    26    26    26    26    36    47            
PRECIP PROB (%)   5     0     5    10    20    80   100   100    70
PRECIP TYPE                               S     S     S     S     S
12 HOUR QPF                0.00        0.00        0.10        0.38
12 HOUR SNOW                0.0         0.0         1.5         6.6
SNOW LEVEL (KFT)0.0   0.0   0.0   0.0   0.0   0.0   0.0   0.0   0.0

Snow and Temperature Measurements


Date: 12/08 24 hr snow  HN24W* High Temp Low Temp Weekly SWE (Monday- Sunday) December Snowfall Season Snowfall HS (Snowpack depth)
Valdez 0 0 30 16 1.48 39 64 38
Thompson Pass 0 0 23 18 1.2 26 145 36
46 Mile 12 12**  13


All snowfall measurements are expressed in inches and temperature in Fahrenheit. 24 hour sample period is from 6am-6am. 

* 24 hour snow water equivalent/ SWE.

** Season total snowfall measurements for 46 mile began December 1st.


Season history graphs for Thompson Pass

















Click on links below to see a clear and expanded view of above Season history graphs


TP WX as of 11/29



Additional Information

Winter weather began early this season, with valley locations receiving their first snowfall on the last day of Summer (September 21st).  Following this storm, above average temperatures and wet weather occurred from late September through early November.  During this time period Thompson Pass received 96 inches of  snowfall by November 7th and Valdez recorded 7.73″ of rain.  

After the 7th of November our region experienced a sharp weather pattern change.  Temperatures dropped below seasonal norms and snowfall became infrequent.  Between the time frame of November 7th- November 28th Thompson Pass only reported 19″ of snow with 1.1″ of Snow water equivalent (SWE).  Temperatures remained below 0° F for most of the period.   This cold/dry weather caused significant faceting of the snowpack, with poor structure the result.

Moderate snowfall returned to our area the last day of November and deposited 6-12 inches of new snow.  The amount varied depending upon the locations’ proximity to the coast.  As the storm exited on the 2nd of December it was quickly replaced by moderate to strong northeast winds.  

On 12/5-12/6 Valdez received 2 feet of new snow with Thompson Pass reporting 16″.  Blaring red flags like collapsing, shooting cracks and propagation in stability tests were immediately present.  This indicates we have moved into persistent slab avalanche territory.



The avalanche hazard is Considerable at all elevations.  Triggering an avalanche 2-3 feet deep will be likely today that could injure, bury or kill a person.  Careful snowpack assessment and conservative terrain management will be necessary today if you choose to travel in avalanche terrain.


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