Forecast Expired - 12/07/2021

Above 4,000ftConsiderable

2,000 to 4,000ftConsiderable

Below 2,000ftConsiderable

Degrees of Avalanche Danger

Avalanche Problems

Problem 1

Storm Snow:

A strong winter storm will be affecting our area on 12/ 6 with additional snowfall of 12-16 inches along with moderate to strong southerly winds.  Increasing temperatures during the last 24 hours have been significant with the Tsaina snotel going from -20 to 20 above in 24 hours!  All of this combined weather will be adding  stress to a weak snowpack.  It will be likely that storm slabs will be reactive to human triggers in terrain steeper than 35°.  This will be especially true in convex or wind loaded terrain.  Avoid large avalanche paths and runouts.


A greater concern will be storm slabs stepping down into persistent weak layers deeper in our snowpack and creating larger more destructive avalanches.



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


  • Historic
  • Very Large
  • Large
  • Small


  • Increasing
  • Steady
  • Decreasing

Problem 2

Persistent Slab:

Very weak snow exists in our snowpack buried 1.5-2 feet in depth.  This weak snow (facets) are being stressed by new snowfall, wind and rising temperatures.  If our area receives the forecasted 2-3 feet of snow out of this storm it is possible that these layers will fail naturally.  Wether they fail naturally or not, human triggered avalanches will be likely that could injure, bury or kill a person.



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

Avalanche Activity

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

Northeast Prince William Sound-
Including the cities of Valdez and Thompson Pass
446 AM AKST Mon Dec 6 2021


* WHAT...Heavy snow occurring. Total snow accumulations of 16 to
  30 inches.

Point forecast for Thompson Pass


Snow. Areas of blowing snow after noon. High near 26. South wind 15 to 20 mph, with gusts as high as 30 mph. Chance of precipitation is 100%. Total daytime snow accumulation of 2 to 4 inches possible.
Snow. Areas of blowing snow before 3am. Low around 16. Southeast wind around 20 mph, with gusts as high as 30 mph. Chance of precipitation is 100%. New snow accumulation of 3 to 5 inches possible.
A 50 percent chance of snow. Areas of blowing snow after 3pm. Mostly cloudy, with a high near 19. East wind 10 to 15 mph becoming north 20 to 25 mph in the afternoon. Winds could gust as high as 30 mph.
Tuesday Night
Scattered snow showers between 9pm and 3am. Areas of blowing snow. Mostly cloudy, with a low around 8. North wind around 30 mph, with gusts as high as 40 mph. Chance of precipitation is 30%.
Partly sunny, with a high near 8. North wind 10 to 15 mph, with gusts as high as 20 mph.
Wednesday Night
Areas of blowing snow after 9pm. Partly cloudy, with a low around 3. North wind 15 to 25 mph.
Snow likely, mainly after 3pm. Areas of blowing snow before 9am. Mostly cloudy, with a high near 16. Chance of precipitation is 70%.

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

DATE             MONDAY 12/06            TUESDAY 12/07           
TIME (LT)        06    12    18    00    06    12    18    00    06
CLOUD COVER      OV    OV    OV    OV    OV    OV    OV    OV    BK
CLOUD COVER (%) 100   100   100   100    75    75    70    85    55
TEMPERATURE      20    25    22    20    18    15    13    10     8
MAX/MIN TEMP                 26          17          19           8
WIND DIR          S     S    SE    SE     E    NE    NE    NE     N
WIND (MPH)       19    20    24    21    12    10    20    20    12
WIND GUST (MPH)  36    41    44    40          32    37    37      
PRECIP PROB (%) 100   100   100   100    50    60    20    30    10
PRECIP TYPE       S     S     S     S     S     S     S     S      
12 HOUR QPF                0.39        0.41        0.07        0.03
12 HOUR SNOW                5.4         5.9         0.1         0.0
SNOW LEVEL (KFT)0.1   0.0   0.1   0.4   0.3   0.0   0.0   0.0   0.0

Snow and Temperature Measurements


Date: 12/06 24 hr snow  HN24W* High Temp Low Temp Weekly SWE (Monday- Sunday) December Snowfall Season Snowfall HS (Snowpack depth)
Valdez 13 .66 25 17 .66 26 51 30
Thompson Pass 4-6″ N/O wx station down wx station down N/O
46 Mile Trace 0 27 -9 0 5 5**  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.  This moderate outflow wind event resulted in the formation of wind slabs that were very reactive to human triggers.  This is yet another sure indicator of the weaknesses present in our snowpack.



The avalanche hazard is Considerable at all elevations.  Heavy snowfall and moderate to strong winds will create dangerous avalanche conditions.  Human triggered avalanches are likely up to 3 feet deep.


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