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ARCHIVED - Forecasts expire after 24 hours.
Issued
Fri, March 21st, 2014 - 7:00AM
Expires
Sat, March 22nd, 2014 - 7:00AM
Forecaster
Graham Predeger
Avalanche risk The Bottom Line

A MODERATE avalanche danger continues to persist above treeline where weak snow exists above and below a series of crusts.   The probability of triggering a large avalanche today is low but the consequences remain high making safe travel protocol in the mountains right now absolutely critical.

Below treeline and on slopes under 35 degrees the avalanche danger is  LOW  today.

Please take a look at the Observations page for several write-ups CNFAIC staff has been able to compile of some of last weekends large, human-triggered avalanches.

Special Announcements

Come join CNFAIC forecasters this Sunday for a FREE AVALANCHE RESCUE WORKSHOP at Turnagain Pass!   Focus will be on beacon practice through avalanche rescue scenarios.   We’ll meet in the motorized lot at 10:30am and wrap up by 1:30pm.   Skiers and sledders welcome!   Please drop a note to kevin@chugachavalanche.org to reserve a spot for you and your crew, as space is limited.

Fri, March 21st, 2014
Alpine
Above 2,500'
2 - Moderate
Avalanche risk
Treeline
1,000'-2,500'
1 - Low
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
  • 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

Almost a full week has passed now since any reports of major avalanche activity in the backcountry, and with people pushing into bigger terrain without incident yesterday this points toward a stabilizing snowpack. 

We do know however that weak snow still exists below the March 10-14th storm cycle that produced a slab up to 5’ deep.  It is becoming increasingly more difficult to upset this weak layer but if affected the resulting avalanche will be large and potentially un-survivable.  Tracks on a slope do not correlate to stability when dealing with a deep slab avalanche problem.  Shallow spots in a slab are likely areas to trigger an avalanche up to 5’ in depth today.  These may be difficult to recognize but some clues to a shallow, tapering slab include areas near rock or tree outcroppings or directly adjacent to wind-stripped terrain.

                            This photo from the Crested Butte Avalanche Center is a good illustration of how a slab tapers.  
                            Likely trigger spot for this avalanche would be near the lower right corner of the photo where the
                            slab is thin and a human is more likely to affect the weak layer.

If your tolerance for risk is taking you into bigger, steeper terrain today it is fundamental that you and your group exercise safe backcountry travel protocol.  This includes communicating travel plans, escape routes and islands of safety.  Expose only one person at a time on a slope and re-group in safe areas well away from run-out zones.

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

Strong solar radiation late in the day continues to push cornices toward their natural breaking point.  Add a skier or snowmachiner on a ridge in close proximity to one of these backcountry bombs and cornice failure will be possible.   Your best bet to mitigate this problem today and everyday is to give cornices a very wide berth when travelling on ridges and limit your exposure when travelling beneath. 

Weather
Fri, March 21st, 2014

The first day of Spring yesterday did not disappoint with sunny skies, temperatures reaching into the mid-30’s at 1,000′ and light to moderate winds out of the east.  

Today we can expect partly cloudy skies by this afternoon, winds out of the east in the 10-25mph range and temperatures again warming into the mid to high 30’s by the heat of the day.  Looking into the weekend an upper level ridge will persist over the mainland, keeping southcentral Alaska mostly sunny and completely dry at least through early next week.

Observations
Recent Observations for Turnagain Pass
Date Region Location
11/16/23 Turnagain Observation: Tincan Common
11/14/23 Turnagain Observation: Sunburst/Magnum
11/14/23 Turnagain Observation: Seattle Ridge
11/13/23 Turnagain Avalanche: Tincan Trees
11/12/23 Turnagain Observation: Sunburst
11/12/23 Turnagain Avalanche: Goldpan – avalanche
11/11/23 Turnagain Observation: Tincan Common
11/11/23 Turnagain Observation: Taylor Pass – Sunburst
11/10/23 Turnagain Observation: Tincan
11/10/23 Turnagain Observation: Tincan Trees
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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.