Valdez

Forecast Expired - 12/02/2021

Above 4,000ftModerate

2,000 to 4,000ftModerate

Below 2,000ftModerate

Degrees of Avalanche Danger

Avalanche Problems

Problem 1

Wind Slab:

The recent 4-8″ of new snow beginning 11/30 was accompanied by moderate winds in channeled terrain.  Wind direction began as northeast and eventually moved to east and finally southeast as the storm progressed.  Expect to find fresh windslabs on a variety of aspects. Triggering a wind slab 1-1.5 feet deep will be possible today, and may step down to deeper layers in the snowpack (discussed in problem 2) and would create larger, more dangerous avalanches.  Watch for signs of wind slab including: hard snow over soft, shooting cracks, pillowed snow surfaces and areas where the new snow depth varies significantly in a small area.  It is possible for the hazard to increase through the day if winds become stronger and more widespread than forecasted.

Likelihood:

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

Size:

  • Historic
  • Very Large
  • Large
  • Small

Trend

  • Increasing
  • Steady
  • Decreasing

Problem 2

Persistent Slab:

The cold and dry weather in November caused a lot of faceting to occur in the snow, creating a weak snowpack.  At this point it is unclear as to how much stress our snowpack will be able to withstand before failing.  In protected areas, it is unlikely that the 4-8″ of new snow will be enough to tip the scales naturally.  Although, where wind has loaded the new snow into deeper slabs it is possible that avalanches either natural or human triggered could step down to these weak layers creating larger more dangerous avalanches.  While early season conditions exist, snowpack structure will vary from place to place.  Don’t expect to find the same snow stability across the forecast area. Re-assess the snowpack every time you are traveling to a new location.

Likelihood:

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

Size:

  • Historic
  • Very Large
  • Large
  • Small

Trend

  • Increasing
  • Steady
  • Decreasing

Weather

Point forecast for Thompson Pass

 

Today
Snow showers, mainly before 3pm. High near 15. Southeast wind 10 to 15 mph becoming northeast in the afternoon. Winds could gust as high as 30 mph. Chance of precipitation is 80%. Total daytime snow accumulation of 1 to 3 inches possible.
Tonight
Scattered snow showers before midnight, then a slight chance of snow after midnight. Cloudy, with a low around 4. North wind 15 to 20 mph, with gusts as high as 30 mph. Chance of precipitation is 40%.
Thursday
Partly sunny, with a temperature falling to around 0 by 5pm. Northeast wind 20 to 30 mph, with gusts as high as 40 mph.
Thursday Night
Mostly cloudy, with a low around -9. Wind chill values as low as -35. Northeast wind around 30 mph, with gusts as high as 40 mph.
Friday
A 30 percent chance of snow after 3pm. Partly sunny, with a high near -8. Northeast wind 30 to 40 mph, with gusts as high as 45 mph.
Friday Night
Partly cloudy, with a low around -8. Northeast wind around 40 mph.
Saturday
Mostly sunny, with a high near 1.
Saturday Night
A chance of snow after 3am. Partly cloudy, with a low around -4.
Sunday
A chance of snow. Partly sunny, with a high near 8.
Sunday Night
A chance of snow. Mostly cloudy, with a low around 0.
Monday
Snow likely. Mostly cloudy, with a high near 16.
Monday Night
Snow likely. Cloudy, with a low around 9.
Tuesday
Snow likely. Cloudy, with a high near 18.

 

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

 
DATE             WEDNESDAY 12/01         THURSDAY 12/02          
TIME (LT)        06    12    18    00    06    12    18    00    06
CLOUD COVER      OV    OV    OV    OV    OV    BK    SC    BK    OV
CLOUD COVER (%)  90    95    95    90    70    55    45    70    75
TEMPERATURE      17    14    12    10     7     4    -1    -4    -6
MAX/MIN TEMP                 17           5           9          -6
WIND DIR         SE     W    NE    NE    NE    NE    NE    NE    NE
WIND (MPH)       10     4    11     9    14    20    21    18    16
WIND GUST (MPH)  27    23    29    31    34    41    41    40    42
PRECIP PROB (%)  80    60    40    20    10     5     5    10    20
PRECIP TYPE       S     S     S     S                             S
12 HOUR QPF                0.17        0.05        0.00        0.00
12 HOUR SNOW                2.4         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: 12/01 24 hr snow  HN24W* High Temp Low Temp Weekly SWE (Monday- Sunday) December Snowfall Season Snowfall HS (Snowpack depth)
Valdez 8.5 .3 27 21 .3 8.5 34 11
Thompson Pass ~6 ~.4 21 0 .5 6 125 N/O
46 Mile 4 .24 8 4 .24 4 4**  

12

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 present as of 11/30 in all three forecast zones.

 

Announcements

The avalanche hazard is Moderate at all elevations.  Human triggered avalanches will be possible today on specific terrain features. The most likely place to trigger an avalanche will be on terrain steeper than 32°, where the 4-8″ of new snow has been redistributed into deeper and stiffer slabs by wind.

 

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