Conditions remain similar to yesterday, in many areas 6-12 inches of uncohesive (no slab) snow sits atop a layer of unreactive wind damaged snow. Human triggered avalanches up to 1 foot+ deep will be possible on lee aspects that have been loaded with this new snow by recent winds, creating cohesive snow (slab). Wind slabs could exist on a variety of aspects due to changing wind directions.
Good stability was observed on 12/29 above brush line where 6 inches of uncohesive snow existed above a hard base. Stability assessment should be fairly straightforward today. Watch for where and if recent wind has redistributed new snow. Hard snow over soft at the surface, shooting cracks, and collapsing are all indicators of a wind loaded slope with the potential to produce an avalanche. Terrain to be cautious of includes: lee side of high elevation ridge lines, cross loaded gullies and steep convex terrain.
The hazard will be lower in areas where surface snow is unaffected by wind.
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 above 3000′, making a person or machines weight unlikely to directly affect these layers. Below brush line where a more protected snowpack is in place, significant facets exist in the bottom half of the snowpack.
It has been 2 weeks since the last significant snowfall event, and stability tests that directly target these layers have not been producing significant results above brush line. Below brush line propagation in stability tests was observed as recently as 12/29 in the Continental zone.
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 or rapid warming. 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 in steep open places, 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
...STRONG LOW TO BRING WINDS AND WINTRY MIX TO SOUTHCENTRAL THIS
We continue to monitor the potential for an impactful weather
event to occur across Southcentral this weekend.
A storm-force low will enter the northern Gulf of Alaska Saturday
afternoon through the evening, bringing a storm-force front first
to Kodiak Island, then to the northern Gulf, including Prince
William Sound and Passage Canal on Sunday. Gusty easterly winds
are likely through Portage Valley and Turnagain Arm, beginning as
early as Saturday night.
Accompanying this area of low pressure is a deep fetch of
moisture which will also introduce warmer temperatures. This will
likely result in a wintry mix of precipitation including rain,
snow, freezing rain, sleet, or a combination of all throughout the
event. Weather models are still struggling to resolve forecast
details, and precipitation type remains the biggest challenge.
At this time, we are confident that the front will begin to impact
Kodiak Island Saturday afternoon, and the southern Kenai
Peninsula Saturday night into Sunday morning. As this system
lifts northward, it will then affect the Anchorage Bowl, Matanuska
Valley, and southern Copper River Basin during the day on Sunday,
when the bulk of precipitation is expected to occur.
Please monitor the forecast closely. We will be making frequent
updates as we work to refine these details, especially regarding
NWS Point forecast for Thompson Pass
Date Friday 12/30/22 Saturday 12/31/22
Time (LT) 06 12 18 00 06 12 18 00 06
Cloud Cover OV OV OV OV OV OV OV OV OV
Cloud Cover (%) 90 95 90 85 80 90 85 95 100
Temperature 8 13 17 17 20 20 24 19 22
Max/Min Temp 17 16 24 19
Wind Dir NE SE E SE SE E E E E
Wind (mph) 4 3 4 3 4 9 6 14 12
Wind Gust (mph) 27 24 20 34 40
Precip Prob (%) 60 50 40 50 40 50 40 70 90
Precip Type S S S S S S S S S
12 Hour QPF 0.04 0.08 0.04 0.22
12 Hour Snow 0.3 0.0 0.0 2.8
Snow Level (kft) 0.4 0.6 0.6 0.5 0.4 0.2 0.1 0.0 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 the seasons weather history.
Valdez Weather History
The avalanche hazard is moderate at all elevations. Once again, the hazard today primarily involves windslabs. Avalanche hazard will be concentrated to areas where the new 6-12 inches of low density new snow has been loaded by recent winds. Human triggered avalanches up to 1 foot in depth are possible in specific terrain, natural avalanches are unlikely.
Posted by Gareth Brown 12/30 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.
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