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ARCHIVED - Forecasts expire after 24 hours.
Issued
Sat, January 4th, 2014 - 7:00AM
Expires
Sun, January 5th, 2014 - 7:00AM
Forecaster
Kevin Wright
Avalanche risk The Bottom Line

**************************12pm update******************************************

An Avalanche Warning has been issued for the forecast area, beginning at 5pm today and ending at 5pm Sunday January 5th.   Hazard will increase to HIGH at the end of the day and remain elevated into tomorrow.

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Our condolences go out to the family that lost a dog in an avalanche on Tincan yesterday.  Numerous avalanches  were reported over the last 2 days.  Combined with a storm coming in today, the danger rating is  CONSIDERABLE for persistent slab and storm snow concerns.  The danger rating will increase as the storm snow builds today.

The avalanche problem as we saw yesterday is undeniably dangerous.  Avalanches are ripping out remotely, large, and full depth.  Extra caution is absolutely essential through the weekend and steep terrain should be avoided completely.

Special Announcements

Thanks to everyone who sent us observation information from the last couple days.  This is potentially life-saving information for all backcountry users this weekend.

Sat, January 4th, 2014
Alpine
Above 2,500'
3 - Considerable
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. 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
  • 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

A busy couple days in the backcountry brought a lot of avalanche activity through Turnagain Pass and Summit.  On Thursday a group of skiers triggered at least 5 disconnected avalanches remotely from the ridge (See color picture below).  Yesterday, a dog triggered an avalanche on the lower part of Tincan ridge (black and white photo below).  Despite the search efforts of at least a dozen people, the dog was not found and is presumed dead.  For reference, this is the same slide path that slid almost exactly a year ago.

Other reported avalanches include – Eddies, south and west aspectsSunburst – SW aspectSeattle ridge – Bowl 2.  (Click on links to go to observations and more photos)

These avalanches are sliding on older and deeper weak layers.  Once they get moving the entire depth of the snowpack can get stripped out.  They are unmanageable in size, will trigger remotely, and can connect across large distances.  

Terrain management is key to safe travel this weekend.  This means stay off steep slopes and avoiding terrain traps and complex terrain.

 

 

Black and white photo – lower CFR, Tincan ridge.  Crown at 2300 feet elevation

Upper Tincan ridge.  Crowns near 3500 feet elevation.

Avalanche Problem 2
  • Storm Slabs
    Storm Slabs
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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

New storm snow will exacerbate the persistent slab problem today as new stress gets added to the snowpack.  By late today, the storm snow on its own may be deep enough to be its own distinct problem.  

With over a foot of snow expected (possibly 2+ feet), we can expect natural avalanche activity to start late today and continue over night.  We will likely reach HIGH avalanche danger during the peak of this storm.

Weather
Sat, January 4th, 2014

The last major storm was over the Dec 31st/Jan 1st holiday.  Since then conditions have been mild and pleasant.

A big change is in the forecast today.  A powerful storm is directing a moisture laden southern jet stream from warm lower latitudes straight at southcentral Alaska.  The picture below describes the scenario far better than I could in words.  

Snowfall is expected to start this morning and increase in intensity this afternoon and into the evening.  Wind will be associated with this storm with a ridgetop wind from the East at 56-73mph.  Rain at sea level is expected, transitioning to snow at 300-400 feet.  Storm totals are predicted in the 16″-29″ range for the next 24 hours.  

Observations
Recent Observations for Turnagain Pass
Date Region Location
03/28/24 Turnagain Observation: Sunburst
03/27/24 Turnagain Observation: Tincan Trees
03/26/24 Turnagain Observation: Cornbiscuit
03/25/24 Turnagain Observation: Tincan
03/22/24 Turnagain Avalanche: Magnum Northwest Aspect
03/21/24 Turnagain Observation: Sunburst
03/21/24 Turnagain Observation: Tincan Proper North Aspect
03/20/24 Turnagain Avalanche: Seattle Creek Drainage
03/19/24 Turnagain Observation: Tincan CFR
03/18/24 Turnagain Avalanche: Tincan – Eddies – 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.