Valdez

Forecast Expired

Above 3,000ftConsiderable

1,500 to 3,000ftConsiderable

Below 1,500ftConsiderable

Degrees of Avalanche Danger

Avalanche Problems

Problem 1

Wind Slab:

Likelihood:

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

Size:

  • Historic
  • Very Large
  • Large
  • Small

Trend

  • Increasing
  • Steady
  • Decreasing

Problem 2

Storm Snow:

Likelihood:

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

Size:

  • Historic
  • Very Large
  • Large
  • Small

Trend

  • Increasing
  • Steady
  • Decreasing

Problem 3

Persistent Slab:

Likelihood:

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

Size:

  • Historic
  • Very Large
  • Large
  • Small

Trend

  • Increasing
  • Steady
  • Decreasing

Avalanche Activity

2/8: Many full path avalanches were reported running around Valdez glacier lake.

2/6: 2 remote triggered avalanches on RFS at 1800-2000′.

  • SS-ARr-R1-D1-O, N aspect, 60′ wide, 50 cm crown, 1800′, failed on buried near surface facets.
  • SS-ARr-R3-D1.5-O, N aspect, 100′ wide, ~60 cm crown, 2000′, failed on buried near surface facets.

Photo of 1st remote trigger listed

-Natural avalanches observed on south aspect at mile 40, ~1800′, 1-2 feet deep and ~100′ wide. SS-NL-R2-D1.5-O.  These were triggered by small snow sluffs.

2/2: Numerous Small pockets of unsupported terrain released naturally in the tsaina valley below 2000′, 2′ deep.

1/27-1/30: Naturals were observed on RFS, N aspect ~6000′,

Avalanches were also observed on -40.5 mile, ~5000′ ,W aspect, 60 m crown

– 2 paths on Three Pigs, ~5000′, SE aspect, ran into the top 1/3 of aprons.

– 3 slides on Billy Mitchell ranging from 3000′-6000′, NW- N aspect.  The most significant was on the upper bowl of cry babys, ~5000′, ~200 m crown, 1-2 meters deep.  

1/23- Found fresh debris in a gully off point 3848′ behind the airport.  D2, ran ~2000′.

~ 1/10- There have been several natural windslabs that have released in the Thompson Pass region:

-South slope of catchers mitt, near 27 mile icefall,~3500′, ~300m wide ,~3′ deep, ran 500′ HS-N-R3-D2.5.  Photo shows extent of crown, which may have been bigger and is now filled in by wind transported snow.

– Gully Between Little and Big Oddessey, NW, 4000′, ~60 M wide, ~2-4′ crown, ran 1000′

-Averys, ~4000′, SW, ~70 M wide, ran ~1000′

1/11- Two natural wind slab avalanches observed at moonlight basin, 2500′-2800′, S aspect.  

The first was on the small last roll before the road and had debris chunks up to 3′ deep “crown filled in by wind”, 200′ wide.

The second was in a cross loaded gully ~ 300′ above the road, with a crown up to ~10′ deep, ~100′ wide.

 

 

Weather

1/9- Light to moderate snowfall will continue for Thompson Pass through Sunday.  As the front passes temperatures will begin to cool and outflow winds will begin.

 
The Thompson Pass Mountain Forecast covers the mountains (above
1000 ft) surrounding Keystone Canyon through Thompson Pass to
Worthington Glacier.

This forecast is for use in snow safety activities and emergency
management.

                   Today        Tonight

Temp at 1000`      35 F         26 F

Temp at 3000`      25 F         19 F

Chance of precip   80%          80%

Precip amount
(above 1000 FT)    0.32 in      0.25 in

Snow amount
(above 1000 FT)    3-6 in       2-4 in

Snow level         900 ft       400 ft

Wind 3000` ridges  SW 10-27 mph SW 4-22 mph

Remarks...None.
  24h snowfall (inches) HN24W (inches)* Hi Temp (F) Low Temp (F) February snowfall Season Snowfall Snow height 
Valdez 8 1.35 35 28 24 132 58
46 mile 3 .24 35 31 10 71 25

Thompson Pass “DOT”

16 1.84 26 22 397

 HN24W= total water received last 24 hours in inches

Thompson Pass weather history 19/20 season beginning 12/21 through 1/23.  Click on links below to see full size image.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

TP DEC 19

TP Jan 2020

TP Feb 2020

 

Additional Information

Our area received 1 1/2 feet of new snow on 2/8.  This new snow came in warm and wet and fell upon a foot of drier snow. This has caused the upper portion of the snowpack to become top heavy.  Below the new snow from the last week, exists a variety of different snowpacks whose strength varies depending upon location and elevation. 

Prolonged arctic temperatures in January have created a weak snowpack.  Weaknesses in our snowpack are pronounced at old rain crusts where moisture was once concentrated, and has now formed facets. These rain crusts exist up to 3000′.  Near surface facets were also formed in January and are spatially variable depending on their exposure to previous wind events.

Poor stability exists below 2500′ in the Thompson Pass region.  Near surface facets up to 2 mm exists that are now buried under 2-3 feet of snow.  This layer is especially prominent in areas that were protected from strong wind in January and north of Thompson pass where temperatures were colder.

Prior to the 2/8 storm stability improved as you go up and became good above 3000′.  Strong outflow wind events in January did not allow near surface facets to be preserved. A very strong layer of wind affected snow exists under 2-3 feet of snow that fell beginning on the 26th of January.  This wind affected snow is creating a bridging effect above a faceted mid and lower snowpack.  In alpine areas that were protected from January wind events persistent weak layers will be present in the upper snowpack that could still be reactive.

There is a high degree of spatial variability in our area.  Careful snowpack assessment will necessary slope by slope.  If you find good stability in one area don’t assume that the next place you go will be the same.

Forecast Confidence is Moderate.

Resolution is low 

 

Near surface facets found at 3000′ on Billy Mitchell 1/19. 2 MM grid.

 There have been limited observations from interior locations due to low snow at lower elevations.   Use caution if you travel in these areas.

If you see something in the mountains that could contribute to this forecast, leave a public observation.  The more observations we receive, the better we can tune our forecast. If you would rather not post an observation publicly, feel free to send me an email at [email protected]

Be aware that the elevation bands have changed on our website.  Low is now below 2000′, Mid is 2000-4000′ and high is 4000′ and above. 

 

 

 

Announcements

The avalanche hazard is considerable at all elevations. Thompson Pass reported 16 inches of snow with 1.84 inches of snow water equivalent.  Warm temperatures and heavy snowfall have created an upside down upper snowpack that will make human triggered avalanches likely and natural avalanches possible.  Travel in avalanche terrain is not recommended today.