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ARCHIVED - Forecasts expire after 24 hours.
Issued
Mon, December 16th, 2013 - 7:00AM
Expires
Tue, December 17th, 2013 - 7:00AM
Forecaster
John Fitzgerald
Avalanche risk The Bottom Line

The avalanche hazard is MODERATE today above and below treeline.   Snowfall that occured over this past weekend has deposited soft slabs up to 18 € in depth.   These slabs will be sensitive to human triggers today on all aspects and elevations.   Human triggered loose snow sluffs will also be a concern in steep terrain today.  

Special Announcements

Join us for a FREE Fireside Chat tomorrow, Tues Dec 17th at 6:30pm at the Alaska Avalanche School in Anchorage.   The topic is Snowpack & Mountain Weather.

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All motorized areas on the Chugach National Forest remain closed due to low snow cover.   We’ve made some headway this weekend towards an opener but we’re not there yet.   Stay tuned later in the week for an update.

Mon, December 16th, 2013
Alpine
Above 2,500'
2 - Moderate
Avalanche risk
Treeline
1,000'-2,500'
2 - Moderate
Avalanche risk
Below Treeline
Below 1,000'
2 - Moderate
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
  • Persistent Slabs
    Persistent Slabs
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.
More info at Avalanche.org

The storm that dropped 12-18” of new snow on Turnagain Pass came down with very little wind and relatively cold temperatures.  The rate of loading was slow enough to not create widespread natural activity.  Over time this new light density snow has formed into more cohesive slabs.  Yesterday we received numerous reports of low volume slab activity around Turnagain Pass.  All activity observed and reported yesterday ran on a crust that formed earlier in December.

The crust that exists below this new snow is fairly uniform in its distribution (i.e. is similar on all aspects and elevations).  The new snow is also uniform in its distribution.  The interface between this crust and new slab has shown poor bonding in many areas.  As such, all aspects above and below treeline are harboring soft slabs that will continue to be sensitive to human triggers.  Throw in the occasional pocket of buried surface hoar into the mix and it becomes trickier to figure out where the most sensitive areas are.  Your best bet for avoiding this problem today is to stick to lower angled terrain.

Graham-Seattle 12-15-13

Soft slabs triggered remotely in steep terrain off of Seattle Ridge.  (photo: Wagner)

Avalanche Problem 2
  • Dry Loose
    Dry Loose
Dry Loose
Dry Loose avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.
More info at Avalanche.org

Loose snow avalanches will begin to come into play a bit more today with cold temperatures helping to weaken the snow surface.  Expect sluffs to run slowly and be low volume.  Pay attention to sluffs in steeper terrain where terrain traps are present.  While the volume will be low the chances for injury will go up if you are knocked over and carried into trees, over rocks or into gullies.

Weather
Mon, December 16th, 2013

The mountains around Eastern Turnagain Arm picked up a trace of new snow in the past 24 hours.   Winds have been light out of the Northwest and temperatures have averaged in the single digits F.   Ridge top temperatures early this morning are hovering around 0 degrees F.

Clear and cold is in store today as a ridge of high pressure has built into the area.   Winds will be light out of the North and Northwest.

Weather conditions will remain similar over the next several days.   The next chance for precipitation looks to be late Wednesday into Thursday.

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.