The Avy Rose shows the forecasted danger by elevation and aspect.
It adds more detail about where you are likely to find the dangers mentioned in the forecast. The inner circle shows upper elevations (mountain top), the second circle is middle elevations, and the outer circle represents lower elevations.
Think of the Rose as a birds-eye view of a mountain, looking down from above. The rose allows our forecasters to visually show you which parts of the mountain they are most concerned about.
The main stability concern today will once again be wind slabs on lee aspects (SE-NW). These will be possible to trigger in specific locations up to 1 foot deep. Cross loaded gullies, the lee side of terrain features and lee of ridge lines will be the areas where windslabs exist. Windslabs may exist further down from ridge lines than you may expect due to the strength of the latest wind event.
On 12/24 windslabs were found to be 4-6 inches deep and stubborn to triggers. Depth and sensitivity of recent windslabs may vary from place to place. Deeper windslabs likely exist in isolated locations. Pay attention to where winds have deposited slabs and investigate the depth and sensitivity in the area that you choose to travel to asses the hazard.
The hazard for this problem may increase during the day if new snow and wind arrives earlier and heavier than forecasted. By Monday morning new snow and strong wind will likely move the avalanche hazard to Considerable.
Faceted snow near the base of the snowpack has been identified in all three forecast zones. In most locations above brush line, faceted snow is capped by pencil-knife hard wind affected snow. This has created a strong bridging affect making a person or machines weight unlikely to directly affect these layers.
Our area received 3-4 inches of snow water equivalent over a 5 day period beginning 12/11. This put significant stress on these weak layers. Natural avalanches did occur, but activity was not widespread and natural avalanches were mostly confined to the storm snow. This points to the strength of the wind hardened snow overlying the weak facets at the base of our snowpack.
It has been eight days since the last significant snowfall event, and stability tests that directly target these layers have not been producing significant results since. One exception was an interior location just north of our continental forecast zone where propagation in stability tests still existed on 12/18.
Persistent weak layers are tricky to assess and are notorious for surprising people. As long as temperatures remain cold and our snowpack is thin, these weak layers will continue to lose strength. It is likely that facets will reactivate in the future when stress is being applied through dramatic changes in weather such as: significant snow accumulation, rapid warming and wind loading. Maintaining safe travel protocols such as skiing one at a time and avoiding traveling in or above terrain traps will increase your safety margin.
The most likely areas to trigger a persistent slab avalanche would be in steep terrain that was protected from previous strong winds that have occurred this season. This could be below brushline or in areas of terrain that are typically spared from outflows. The Continental zone remains suspect as this area has a weaker snowpack and generally receives less wind, which would decrease the bridging affect mentioned above.
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 a natural avalanche consider leaving a public observation.
Valdez Avalanche Activity
No recent avalanche activity has been recorded in the last 7 days.
Check out our updated weather tab! A collection of local weather stations are available for viewing with graphs and tabular data included.
NWS Watches and warnings
Northeast Prince William Sound-
Including the cities of Valdez and Thompson Pass
435 AM AKST Sun Dec 25 2022
...WINTER WEATHER ADVISORY IN EFFECT FROM 6 PM THIS EVENING TO
9 AM AKST MONDAY FOR THOMPSON PASS...
* WHAT...Snow and blowing snow expected. Total snow accumulations
of 4 to 8 inches. Winds gusting as high as 55 mph. Visibility
reduced to one half mile.
* WHERE...Thompson Pass.
* WHEN...From 6 PM this evening to 9 AM AKST Monday.
NWS Point forecast for Thompson Pass
Date Sunday 12/25/22 Monday 12/26/22
Time (LT) 06 12 18 00 06 12 18 00 06
Cloud Cover BK OV OV OV OV OV OV OV OV
Cloud Cover (%) 65 80 95 95 90 95 95 95 95
Temperature 7 7 8 17 20 22 26 26 26
Max/Min Temp 8 7 27 25
Wind Dir NE NE NE NE NE NE E SE SE
Wind (mph) 11 14 19 16 16 16 14 13 9
Wind Gust (mph) 39 48 52 50 46 40 27
Precip Prob (%) 5 5 40 60 60 70 60 50 50
Precip Type S S S S S S S
12 Hour QPF 0.01 0.27 0.30 0.14
12 Hour Snow 0.0 3.6 4.1 0.7
Snow Level (kft) 0.2 0.0 0.3 1.1 1.1 0.6 0.7 0.5 0.3
Click on link below for Thompson Pass weather history graph:
*HN24W- 24 hour Snow water equivalent in inches
*SWE– Snow water equivalent
**46 mile seasonal snowfall total begins December 1st.
Click on the link below for a running summary of this seasons weather history of our area.
Valdez Weather History
The avalanche hazard is moderate at all elevations. The main hazard today will be triggering a wind slab avalanche that could be 1 foot deep. Human triggered avalanches are possible in specific locations and natural avalanches are unlikely. The hazard will increases this evening once 4-8 inches of new snow arrives along with strong E-NE winds.
Posted by Gareth Brown 12/25 7:40 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.
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