Valdez

Forecast Expired - 04/22/2023

Above 4,000ftModerate

2,000 to 4,000ftModerate

Below 2,000ftModerate

Degrees of Avalanche Danger

Avalanche Problems

Problem 1

Wet Avalanches:

The strength of the Spring sun is in full affect and with it comes a variety of avalanche problems.   These include wet loose, cornice/ice fall, wet slab and glide crack avalanches.

 

Wet loose avalanches will be the most common problem to encounter today.   This is the last day of a clear weather cycle before cooler weather and clouds arrive Saturday, expect for wet loose activity to be on the increase during the day. This occurs when the sun heats up the snow surface enough to become wet and lose strength. This process creates point release slides that entrain more snow as they move down hill.  These can be small-very large depending upon the steepness and relief of the slope they occur on.  Wet loose activity goes through a daily cycle with east aspects being the first to lose strength then moving to south and finally west.  Steep rocky terrain is the most easily affected due to rocks soaking up the suns energy and transferring it into the surrounding snow.

   Other hazards of the spring include cornice fall.  This is a problem with a lower likelihood, although  currently poses the greatest danger to  people traveling in avalanche terrain.  Cornices are losing strength each day as they are baking in the sun.  Avoiding exposure to cornices is highly recommended.  Two cornice fall events in the last week have resulted in very large natural avalanches, with multiple step downs occurring resulting in failure at the ground (see avalanche activity section).

 

Avoid traveling on or below steep solar aspects during the heat of the day and traveling on or exposing yourself to cornices.

 

 

Likelihood:

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

Size:

  • Historic
  • Very Large
  • Large
  • Small

Trend

  • Increasing
  • Steady
  • Decreasing

Problem 2

Persistent Slab:

Triggering a persistent slab avalanche remains possible 1-2 feet in depth, although the likelihood is decreasing as more diurnal melt freeze cycles occur.  Near surface facets and buried surface hoar have been identified 6 inches -2 feet deep in mid -upper elevation shaded terrain.  This weak layer has recently been unreactive in snowpits and to ski cuts the last few days, although human triggered avalanches have been reported as recently as 4/17.  Near surface facets and buried surface hoar exist in specific locations and may remain reactive in isolated locations where storm totals from early April are deeper (>18 inches).

 

Settled storm snow depths since 4/5 vary significantly across our forecast zone, with some areas only having a few inches and others having as much as 2 feet on upper elevation north facing terrain.  Assess the depth and sensitivity of the interface between the settled powder at the surface and hard older layers beneath on a slope by slope basis.

 

Deeper in the snowpack faceted snow exists in most location at and below hard wind affected snow surfaces in the mid snowpack (3/17 interface).  A very large natural avalanche occurred on Meteorite on 4/15.  This avalanche was triggered by cornice fall that created a series of step-down avalanches.  This a clear indicator that large triggers can tip the scales on weak layers in the mid and lower snowpack (see problem 4).  The changing of seasons bringing warming temps increases the likelihood for more events similar to Meteorite to occur in the coming weeks.

Likelihood:

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

Size:

  • Historic
  • Very Large
  • Large
  • Small

Trend

  • Increasing
  • Steady
  • Decreasing

Problem 3

Wind Slab:

Moderate north winds on 4/17-18  kicked up through Thompson Pass, high elevation ridge lines and other wind exposed terrain.  Shallow wind slabs formed in specific areas that may be reactive to human triggers less than 1 foot in depth.  Pay attention to wind affect at the surface and the sensitivity of the surface snow where you choose to travel.  Wind slabs may have been deposited on near surface facets that have been forming at the surface during the last couple days of clear weather.  This would make the sensitivity of wind deposits higher in those locations.

 

Winds were light on 4/19 and are forecasted to remain so over the next few days.  This will lower the likelihood of this avalanche problem as time goes on.

Likelihood:

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

Size:

  • Historic
  • Very Large
  • Large
  • Small

Trend

  • Increasing
  • Steady
  • Decreasing

Problem 4

Deep Slab:

This may be the last problem on the list and least likely to encounter, but it is the most dangerous one.   There have been 2 reports in the last 4 days of cornice fall causing very large persistent slabs to full depth avalanches (see avalanche activity section).  Avoiding traveling on or exposing yourself to cornices is highly recommended.

 

Weak snow exists at the base of our snowpack.  On 4/15 our area saw the first deep slab activity occur since late February.  This occurred on Meteorite (see avalanche activity section) and was a cornice fall that triggered a series of step down avalanches that eventually stepped down to the ground.  This is a clear indication that large triggers can have an affect on depth hoar.  Increasing temperatures could produce more significant activity later in the season while our snowpack is undergoing a transition from a winter snowpack to a spring one.  

 

This problem is very difficult to assess due its depth and the fact that signs of instability will likely not be present.  You can stack the odds in your favor by avoiding steep terrain that is undergoing rapid changes such as strong solar and avoiding exposure to large triggers such as cornices.  

 

 

Likelihood:

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

Size:

  • Historic
  • Very Large
  • Large
  • Small

Trend

  • Increasing
  • Steady
  • Decreasing

Avalanche Activity

Below is a summary of observed Avalanche activity from the last 7 days.  Avalanches that were noted earlier in the season can be viewed by clicking the link below.

If you trigger or observe an avalanche consider leaving a  public observation.

Valdez Avalanche Activity

4/17- Large natural avalanche reported on the upper Tasnuna just east of  “The Wall”.  Cornice fall was likely the initial trigger with other sympathetic avalanches occurring as well as full depth step downs. SS-Nc-R2.5-D3

 

– Skier triggered avalanche reported in the Tasnuna valley “The Hammer” SS-ASu-D2-I down 40 cms on 4/7 buried surface hoar/ NE aspect ~5500′.  5th Skier on slope was caught and partially buried in a crevasse/ skier did not sustain any major injuries.

4/15- A cornice fall produced a series of step down avalanches on Meteorite which resulted in failure at the ground.  This intiatied as a cornice fall at 6500′ that triggered an avalanche most likely at the 3/9 interface which then stepped down to a persistent slab around 6100′ NE and stepped down to the ground at 5600′ NE.

 SS/HS-NC-D3-O/G 6200′ NE, step down to ground ~5600′ NE

 

 

Weather

Check out our updated weather tab!  A collection of local weather stations are available for viewing with graphs and tabular data included.

NWS Watches, warnings and advisories

NONE
 NWS Point forecast for Thompson Pass
Today
Sunny, with a high near 45. Northeast wind 10 to 15 mph.
Tonight
Increasing clouds, with a low around 26. North wind around 5 mph.
Saturday
Snow, mainly after 1pm. High near 33. East wind around 5 mph. Chance of precipitation is 80%. New snow accumulation of around an inch possible.
Saturday Night
Snow before 7pm, then snow showers likely, mainly between 7pm and 1am. Low around 21. Northeast wind 15 to 25 mph, with gusts as high as 35 mph. Chance of precipitation is 80%.
Sunday
A 30 percent chance of snow showers before 7am. Cloudy, with a high near 30. Northeast wind 20 to 25 mph, with gusts as high as 35 mph.
Sunday Night
Mostly cloudy, with a low around 19. North wind 25 to 30 mph, with gusts as high as 35 mph.
Detailed forecast for Thompson Pass Mid elevation (2000-4000 Feet)
Date                     Friday 04/21/23         Saturday 04/22/23 
Time (LT)          04    10    16    22    04    10    16    22    04
Cloud Cover        CL    FW    SC    OV    OV    OV    OV    OV    OV
Cloud Cover (%)     5    20    25    70    95    95   100    90    95
Temperature        25    33    44    29    25    30    33    28    22
Max/Min Temp                   44          25          33          21
Wind Dir           NE    NE    NE     E    NE    NE    NE     N    NE
Wind (mph)         12    11     3     2     3     4     8    19    21
Wind Gust (mph)                                                      
Precip Prob (%)     0     0     0     0     5    50    80    60    50
Precip Type                                       S     S     S     S
12 Hour QPF                  0.00        0.00        0.09        0.08
12 Hour Snow                  0.0         0.0         0.5         0.6
Snow Level (kft)  1.3   1.7   2.3   1.6   1.3   1.4   1.5   0.4   0.2
 Click on link below for Thompson Pass weather history graph:

https://docs.google.com/spreadsheets/d/e/2PACX-1vR_Fl5087NrNCo2BtsSaum-gxrx1QioHSO4YqEmjW76LhuDu9ZsSxbBCTl6zkYIFarys-5eM_7P5GpV/pubhtml

 

 

 

Date:

04/21

24 hr snow HN24W* High temp Low temp 72 hour SWE* April snowfall Seasonal snowfall Snowpack Depth
Valdez 0 0 54 33 0 11 248 41
Thompson Pass  0 0 N/O N/O 0 12 438 N/O
46 mile 0 0 49 20 0 ~5 ~116** 45

 

 

*HN24W- 24 hour Snow water equivalent in inches

*SWESnow water equivalent

**46 mile seasonal snowfall total begins December 1st.

Additional Information

 

Click on the link below for a running summary of the seasons weather history.

Valdez Weather History

Announcements

The avalanche hazard is moderate at all elevations.  Multiple avalanche problems currently exist.  The most likely hazard to be encountered today will be wet loose avalanches.  These start out as unlikely during the day and become likely on solar aspects as the sun heats the surface of the snow.  The most dangerous and least likely avalanche problem to be encountered is cornice/ice fall that triggers a deep slab.  Two deep slab natural avalanches have been reported in the last week, these were triggered by cornice fall.   A continued increase in high temps and longer days will slowly increase the likelihood of this problem occurring.  Lastly, there remains the possibility to trigger an avalanche around 1 foot deep on upper elevation shaded aspects that involves weak snow beneath the settled April storm snow. Avoid exposure to cornices and steep solar aspects during the heat of the day.  Assess the interface beneath the settled April storm snow, if traveling in steep and or consequential upper elevation north facing terrain.  

Posted by Gareth Brown 04/21  8:00 am.

 

For a description of current avalanche problems, weather information, season history and more click the (+ full forecast) button.  Avalanche forecasts will be issued Wednesday-Sunday through April 30th.

If you have pictures of recent natural or human triggered avalanches or notice signs of instability such as shooting cracks or collapsing, leave an observation to help improve forecast accuracy.