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ARCHIVED - Forecasts expire after 24 hours.
Issued
Tue, January 28th, 2014 - 7:00AM
Expires
Wed, January 29th, 2014 - 7:00AM
Forecaster
Wendy Wagner
Avalanche risk The Bottom Line

We have a CONSIDERABLE avalanche danger both above and below treeline. With continued unseasonably warm and wet conditions the possibility remains for large wet slab and/or deep slab avalanches to release. These have been full-depth slides consisting of heavy wet snow that can run to valley bottoms. Though the likelihood is decreasing with time and cooler temperatures today the consequences remain high. Steering clear of avalanche terrain and runout zones continues to be prudent.

There is very little to no snow below 1,000′. The danger at this elevation is from above where an avalanche releasing could deposit debris in runout areas and gullies.  

Special Announcements

There are only a few days left to apply for the Rob Hammel Scholarship Fund. This is an avalanche education scholarship sponsored by  The Friends of the CNFAIC and the Rob Hammel family. This is a great opportunity. Deadline to apply is January 31st.  Go to this page for more information.  

Tue, January 28th, 2014
Alpine
Above 2,500'
3 - Considerable
Avalanche risk
Treeline
1,000'-2,500'
3 - Considerable
Avalanche risk
Below Treeline
Below 1,000'
3 - Considerable
Avalanche risk
0 - No Rating
1 - Low
2 - Moderate
3 - Considerable
4 - High
5 - Extreme
Avalanche risk Avalanche risk Avalanche risk Avalanche risk Avalanche risk
Travel Advice Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features. Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern. Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding, and conservative decision-making essential. Very dangerous avalanche conditions. Travel in avalanche terrain not recommended. Extraordinarily dangerous avalanche conditions. Avoid all avalanche terrain.
Likelihood of Avalanches Natural and human-triggered avalanches unlikely. Natural avalanches unlikely; human-triggered avalanches possible. Natural avalanches possible; human-triggered avalanches likely. Natural avalanches likely; human-triggered avalanches very likely. Natural and human-triggered avalanches certain.
Avalanche Size and Distribution Small avalanches in isolated areas or extreme terrain. Small avalanches in specific areas; or large avalanches in isolated areas. Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas. Large avalanches in many areas; or very large avalanches in specific areas. Very large avalanches in many areas.
Avalanche Problem 1
  • Wet Loose
    Wet Loose
Wet Loose
Wet Loose avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.
More info at Avalanche.org

Despite the impressive spike in temperature yesterday at the ridgetops, we did not see or hear of any new avalanche activity. There were a few small wet point releases and one potential small slab in the Summit Lake area that may have occurred. Our last known wet slab was on Turnagain Pass Sunday – two days ago. Photo below.

One thing we have different today is a substantial drop in temperature. This is good news, both for stabilizing the snowpack as well as limiting the melt-out seen below treeline. However, temperatures are still warm in the big picture and though the snowpack continues to season and adjust to the warm conditions, large wet avalanches are still possible. 

Below is the last known wet slab avalanche. It occurred Sunday, January 26th on Pete’s South ridge – South side of Turnagain Pass.

Avalanche Problem 2
  • Deep Persistent Slabs
    Deep Persistent Slabs
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.
More info at Avalanche.org

At the upper elevations (above 3,500′ or so) where snow has been falling for almost two weeks now the snowpack has been getting deeper by the day. We had evidence of a large deep slab avalanche cycle last week, with the last known deep slab three days ago on Goat Mtn. Though it has been a few days since we’ve seen or heard of any new deep slabs, it doesn’t mean the problem has gone away. The pack dealt with a large spike in temperature yesterday (over 40F at 4,200′) and has seen persistent strong wind for over a week. It is not likely anyone will be traveling in this upper elevation terrain, but the possibility exists for natural avalanches to occur and run to valley bottoms.

Additional Concern
  • Announcement
    Announcement

A few comments on the state of the snowpack:

  • Below treeline – the pack is completely wet, unsupportable (mush) and melting out. The Turnagain Pass SNOTEL at 1880′ is reporting 29″ depth (average for the past nine years of available data is 73″). Click here for a few more details and pictures. 
  • Above treeline – the pack starts with around 40″ of wet snow at treeline and becomes much deeper and dryer with elevation. Around 4,000′ and higher the snow is dry enough that wind is able to produce plumes.

All that said, there is still a layer of weak faceted snow that sits near the ground and is responsible for our many slab avalanches seen so far this season. Depending on elevation, the faceted snow is either wet (below treeline) and melting or dry (well above treeline) and being compressed with the weight of the new snow from the past couple weeks.

Below treeline (Turnagain Pass looking Northeast)              Above treeline (South end of Pass looking North at Pk 4940)
    

Weather
Tue, January 28th, 2014

During the past 24-hours we have seen a significant drop in temperature since yesterday morning’s spike (to the low 40’s F on the ridgetops and mid 50’s at sea level). We are now sitting in the upper 20’s at the ridgetops and around 40F at sea level. Winds were averaging 50mph yesterday but have  dropped to 10mph overnight from the East. We had .4″ of rain to 3,500′, mostly falling in the afternoon.

Today we should see the remnants of yesterday’s system move out. Light rain up to 1,500′ is expected to fall during the day with around .2″ accumulating. Skies should be mostly cloudy and could clear up a bit by the afternoon. Temperatures will be in the upper 20’s on the ridgelines and near 40F at sea level. Winds are expected to remain light from the East in the 10mph range.

For tomorrow we should see conditions similar to today but for Thursday a cooling and clearing trend looks to develop.  

Observations
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05/07/24 Turnagain Observation: Turnagain Pass Wet Slabs A S
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This is a general backcountry avalanche advisory issued for Turnagain Arm with Turnagain Pass as the core advisory area. This advisory does not apply to highways, railroads or operating ski areas.
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