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Archives
ARCHIVED - Forecasts expire after 24 hours.
Issued
Fri, January 8th, 2016 - 7:00AM
Expires
Sat, January 9th, 2016 - 7:00AM
Forecaster
Aleph Johnston-Bloom
Avalanche risk The Bottom Line

Today the avalanche danger is  MODERATE  both at Treeline and in the Alpine. Triggering a wind slab is possible today in steep leeward terrain. Be aware of large cornice features and recent glide crack movement and avoid putting yourself on or under these unpredictable hazards. Pay attention to changing conditions as the next storm effects the region.

Below 1000′ the avalanche danger is  LOW  where triggering an avalanche is unlikely.

*Outside of our forecast zone in Summit Lake where a generally thinner snowpack exists triggering a persistant slab 3′ thick is a concern. Cautious route-finding and careful snowpack evaluation is advised. Check out the observations page. The Summit Summary will be updated tomorrow.

Special Announcements

Tommorrow CNFAIC forecasters are hosting a FREE  Avalanche Rescue Workshop  from 11:00am to 12:30pm at the motorized lot on Turnagain Pass.  This is a great opportunity to practice beacon searches, learn strategic shoveling techniques and meet local forecasters! This workshop is open to everyone and anyone (motorized and non-motorized), novices and experts. We hope to see you there!

Filing for the PFD this week? Remember, The Friends of the CNFAIC is part of  PICK.CLICK.GIVE. Your donations are greatly appreciated and an integral part to making the CNFAIC possible and sustainable.  

Fri, January 8th, 2016
Alpine
Above 2,500'
2 - Moderate
Avalanche risk
Treeline
1,000'-2,500'
2 - Moderate
Avalanche risk
Below Treeline
Below 1,000'
1 - Low
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. Dangerous avalanche conditions. 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
  • Wind Slabs
    Wind Slabs
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.
More info at Avalanche.org

Triggering a wind slab today in steep leeward terrain is possible today. Winds over the past few days have deposited additional snow, continuing to cross load and top load terrain features. Look for pillowed snow, listen for hollow sounds and pay attention to stiff snow under your skis, snowboards or snowmachines. Investigate if the stiff snow is overlaying soft snow. Watch for shooting cracks and remember even a small pocket of wind slab in steep terrain can have high consequences. Wind slabs are notorious for letting you travel out onto them and then breaking above you. Evaluate carefully before committing to steep terrain from above or below.

****In some parts of the advisory area 5-7′ of settled and wind effected storm snow is sitting on a layer of old faceted snow on top of the Thanksgiving Rain Crust. This still needs to be a consideration as you travel into the backcountry today. This Deep Slab concern is a low probability, very high consequence set-up.  As always it is important to use safe travel practices: ride slopes one at a time, have an escape route planned, regroup and/or park in safe areas and watch your travel partners. Do not overload slopes with multiple skiers, boarders or snowmachines. 

Wind transporting snow on Turnagain Pass. 

 

Avalanche Problem 2
  • Cornice
    Cornice
Cornice
Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.
More info at Avalanche.org

Very large cornice features have formed throughout the region as a result of a two-week storm that deposited ~9’ of snow and was accompanied by very high winds. Cornices have the potential to fall naturally or be triggered by the weight of a person or machine and can be very dangerous. Travel under or on them should be avoided. They have the tendency to break farther back from the ridge than expected and can trigger an avalanche on the slope below by adding a lot of weight quickly. As you approach ridgelines and the entrances to backcountry bowls make sure you aren’t accidently traveling on overhanging snow. A snowmachine took a dip into the cornice crack near the top of the Seattle Creek uptrack.

A large crack was found on the Magnum ridge above the cornice.

Additional Concern
  • Glide Avalanches
    Glide Avalanches
Glide Avalanches
Glide Avalanches are the release of the entire snow cover as a result of gliding over the ground. Glide avalanches can be composed of wet, moist, or almost entirely dry snow. They typically occur in very specific paths, where the slope is steep enough and the ground surface is relatively smooth. They are often proceeded by full depth cracks (glide cracks), though the time between the appearance of a crack and an avalanche can vary between seconds and months. Glide avalanches are unlikely to be triggered by a person, are nearly impossible to forecast, and thus pose a hazard that is extremely difficult to manage.
More info at Avalanche.org

Glide cracks are continuing to appear throughout Turnagain Pass. They may lead to Glide Avalanches which are incredibly difficult to predict and will be deep and destructive if they do release. Travel under glide cracks should be avoided. In addition the cracks can be quite deep and falling into one could be very hazardous. They are sometimes mistaken for old avalanche crowns. The characteristic “brown frown” shape can help you identify the glide cracks in the terrain. 

 

 

Glide cracks on Seattle Ridge just north of the common uptrack. 

Weather
Fri, January 8th, 2016

Yesterday was mostly overcast. There were a few breaks in the clouds alternating with periods of very light rain/snow showers. Temps were in the 30Fs at 1000′ and in the 20Fs at 3000′. Winds were mostly light from the ENE with a few gusts in the 30s.  

Today will be mostly cloudy with light rain and snow showers, 0-2″ of snow. Snow line is forecasted to be around 1800′. Easterly winds will increase throughout the day into tonight as the storm moves into the region. Precipitation is forecasted to be heavier tonight into tomorrow morning. Snow line may increase to 2000′.

This showery pattern will persist through the weekend as the plume of warm moist air is pushed into the area by the low in the Gulf.

PRECIPITATION 24-hour data (6am – 6am)

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 31   0 0    81
Summit Lake (1400′) 30 0   0  26
Alyeska Mid (1700′) 32 0   0 58  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 23   ENE   15   38  
Seattle Ridge (2400′) 25 n/a   n/a   n/a  
Observations
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Date Region Location
11/16/23 Turnagain Observation: Tincan Common
11/14/23 Turnagain Observation: Sunburst/Magnum
11/14/23 Turnagain Observation: Seattle Ridge
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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.