Forecast Expired - 12/11/2021

Above 4,000ftConsiderable

2,000 to 4,000ftConsiderable

Below 2,000ftConsiderable

Degrees of Avalanche Danger

Avalanche Problems

Problem 1

Persistent Slab:

There is a 2-3 foot deep slab sitting on the November facets.  The depth of this slab increased a bit overnight with 6 inches of snow in Valdez, 3-4 inches on Thompson Pass and 10 inches at 46 mile.  Northeast wind are forecasted to increase over the next 48 hours moving from moderate to very strong.  Both of these changes in weather will make triggering a persistent slab avalanche more likely.


 On 12/8 a remote triggered/sympathetic avalanche event (see observation section) is a clear sign that our persistent slab avalanche problem is hanging on by its fingernails.  This is especially true in wind sheltered areas.  In locations were old wind slabs exist above the November facets, weak layers may be more stubborn to triggers.  But the same weak layer exists and dangerous human triggered avalanches are possible in these locations as well.  


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.  Remotely triggered avalanches are possible (triggering a slope above, below or adjacent to your position).  Pay attention to the terrain above you and what the consequences would be if that slope were to fail.  


Photo of Remote triggered/sympathetic avalanches on 12/8 


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:

As the current storm exits, our area will be setting up for what looks to be a pretty stout outflow wind event (northeast).  Winds are forecasted to go from moderate to very strong over the next 48 hours.   On 12/10 winds look to start out as moderate, which will be the right strength to effectively build wind slabs on lee aspects.  Expect to find fresh wind slabs up to 1 foot in depth that are 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°.  The hazard for this avalanche problem will be increasing over the next 48 hours.







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


  • Historic
  • Very Large
  • Large
  • Small


  • Increasing
  • Steady
  • Decreasing

Avalanche Activity

12/8- Large remote trigger/ sympathetic avalanche event occurred 12/8 with avalanches extending from Gully 1 to Nicks.  Avalanches were soft slabs that ranged in size from D1-D3.  Over 10 separate avalanches were counted with crown depths averaging 2-3′.  One avalanche had a crown length of half a mile while another was triggered over a mile away from the point of collapse.  See observation section for full report and more photos.

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’s 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


Snow showers, mainly before 3pm. Areas of blowing snow before 9am, then areas of blowing snow after noon. High near 18. North wind 15 to 25 mph, with gusts as high as 35 mph. Chance of precipitation is 90%. Total daytime snow accumulation of around an inch possible.
Scattered snow showers before 3am, then a chance of snow after 3am. Areas of blowing snow. Mostly cloudy, with a low around -2. Wind chill values as low as -30. North wind 30 to 35 mph, with gusts as high as 45 mph. Chance of precipitation is 50%.
A 20 percent chance of snow before 3pm. Areas of blowing snow. Mostly cloudy, with a high near 7. Wind chill values as low as -30. North wind 35 to 45 mph, with gusts as high as 55 mph.
Saturday Night
Areas of blowing snow. Partly cloudy, with a low around -6. Wind chill values as low as -40. North wind 50 to 55 mph, with gusts as high as 65 mph.
Mostly sunny, with a high near -5. Northeast wind 15 to 25 mph.
Sunday Night
Mostly cloudy, with a low around -13. Northeast wind 20 to 25 mph decreasing to 10 to 15 mph after midnight.

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

DATE             FRIDAY 12/10            SATURDAY 12/11          
TIME (LT)        06    12    18    00    06    12    18    00    06
CLOUD COVER      OV    BK    SC    BK    OV    OV    BK    FW    FW
CLOUD COVER (%)  90    65    50    65    80    80    55    20    25
TEMPERATURE      17    18     7     2     2     7     0    -4    -6
MAX/MIN TEMP                 19           0           9          -6
WIND DIR          E    NE    NE    NE    NE    NE    NE    NE     N
WIND (MPH)       17    16    23    24    24    27    32    35    21
WIND GUST (MPH)        36    46    47    46    52    58    65      
PRECIP PROB (%)  90    70    40    50    20    20     5     5     0
PRECIP TYPE       S     S     S     S     S     S                  
12 HOUR QPF                0.08        0.04        0.03        0.00
12 HOUR SNOW                1.1         0.0         0.0         0.0
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: 12/10 24 hr snow  HN24W* High Temp Low Temp Weekly SWE (Monday- Sunday) December Snowfall Season Snowfall HS (Snowpack depth)
Valdez 5.5 .1 27 11 1.58 46 70 36
Thompson Pass ~3-4 N/O wx station down wx station down N/O ~30 149 36
46 Mile 10 .6 22 1 .9 22 22**  24


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.  On 12/8 a significant remote/ sympathetic avalanche event occurred from Gully 1 through Nick’s Happy Valley. Incremental loading has resulted in a dangerous persistent avalanche problem at the present.



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.  Avalanches could be triggered from flat terrain, be aware of the terrain above you.  Avoid recently wind loaded terrain steeper than 32°.


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Help to improve your local avalanche center and contribute an observation to the website.  You can also contact me directly at [email protected] (907)255-7690.