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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Sun, January 1st, 2017 - 7:00AM
Expires
Mon, January 2nd, 2017 - 7:00AM
Forecaster
Wendy Wagner
The Bottom Line

There is a MODERATE avalanche danger in the mountains surrounding Turnagain Pass on all slopes above 1,000′ where winds have affected the snow. Triggering a wind slab avalanche on slopes steeper than 35 degrees will be possible. These slabs are hard and sitting on a variety of weak layers. They also have the potential to be triggering from below or when you are well onto them.    

Summit Lake area on the Kenai:  Heightened avalanche conditions exist – Please see Heather’s Snowpack Summary from yesterday if you are considering this zone.

JOHNSON PASS REGION:   This area has a thinner and potentially more dangerous snowpack in open areas where Friday’s winds wreaked havoc. Triggering a slab avalanche is possible on steep slopes loaded by winds – these could be pulled down from below and occur on small steep slopes as well. We are in need of information from this zone (Bottomless snow in the alders? Hard wind slab above the trees? Any avalanche activity?) – please considering submitting an observation if you head this way!!  

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Sun, January 1st, 2017
Alpine
Above 2,500'
Moderate (2)
Avalanche risk
Treeline
1,000'-2,500'
Moderate (2)
Avalanche risk
Below Treeline
Below 1,000'
Low (1)
Avalanche risk
Alpine
Above 2,500'
Avalanche risk
Moderate (2)
Treeline
1,000'-2,500'
Avalanche risk
Moderate (2)
Below Treeline
Below 1,000'
Avalanche risk
Low (1)
Danger Scale:
No Rating (0)
Low (1)
Moderate (2)
Considerable (3)
High (4)
Extreme (5)
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 word on the street is Friday’s wind event…. Very strong winds from the West and South did a number to the snow surface, the snowpack and triggered numerous natural wind slab avalanches. Certain areas are stripped to the ground while others have sastrugi and rock hard wind drifts 2-3′ thick. In general, many slopes sport a variety of 4-8″ supportable wind slabs, thinner breakable wind crusts and even some soft snow in between. Don’t get too down though, there are zones that managed to survive and harbor soft settled snow, but folks seem a bit reluctant to give up the coordinates. The clear (but warm) weather forecast for the next week may start eating away at the hard surfaces and riding conditions could improve.  (Check out what folks reported yesterday HERE.)

PERSISTENT SLAB AVALANCHES (In our current case: Hard WIND SLABS SITTING ON WEAK SNOW):

What to keep in mind and watch for:

  • Wind slabs are likely to be sitting on any number of weak layers (facets and/or buried surface hoar)
  • Look for hard snow over soft snow – slabs can be strong enough to support the weight of a snowmachine or skier, allowing you onto them before they release
  • Triggering a slab from below is possible
  • Slabs on unsupported slopes in steep rocky terrain are prime suspects
  • Listen for whumphing
  • Look for cracking around your snowmachine, skis, board

It may be a busy New Year’s Day – remember safe travel protocols:

  • Expose one person at a time
  • Watch your partners
  • Have an escape route planned
  • Watch for other groups
  • Consider, what will happen if the slope slides?

 
Photo below: Wind damage and older avalanche activity on Magnum’s NW shoulder

 

Large natural wind slab avalanche from Friday on the Northerly aspect of Magnum (back along ridge toward Taylor Pass). Crown mostly filled in, debris ran up other side of creek bed near common up-track to Taylor Pass.

 

Illustrating the complex nature of our snowpack and multiple weak layers:  The Alaska Avlanche School Level 1 course had a CT (compression test) that resulted in three weak layers failing simultaneously on the 21st tap! This is a rare test result (top 2 layers were buried surface hoar and bottom layer was basal facets) Details HERE.

 

Summmit Lake area: Anti-tracks on Manitoba Mtn. Similar to scoured areas in Turnagain Pass. (photo J Haffener & S Galoob)

 

Additional Concern
  • 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

Watch for cornices in unusual places from the Dec 30 wind event. Though these may seem rock hard and welded into place, it’s good practice to always give them a wide berth – we do have warm, sunny weather on tap and this can help to weaken them.

Friday’s Southwesterly winds across Sunburst ridge attempted to strip the large cornices formed by the predominately Easterly winds.

Weather
Sun, January 1st, 2017

Mostly overcast skies filled the area yesterday. Ridgetop winds were light from the South and West. Temperatures were in the upper 20’s F on the ridgelines and lower 20’s F in the parking lots.

Today, we should see sunny skies with WARM and breezy conditions. A very warm air mass is over us associated with a “Blocking High Pressure”. Temperatures will be near 32F on the ridgelines and in valley bottoms a bit cooler, in the 20’s F. Ridgetop winds are slated for 5-15mph from the South and West.

The high pressure in place looks to remain through the week. From the NWS: “there is high confidence in a prolonged dry spell over Southcentral Alaska and Kodiak Island, on the order of 7 days or longer”. Yes, not anything snow lovers want to hear.  The next chance for snow does not show up in the longer range model runs, yet – fingers crossed!

*The new year is creating a glitch in some weather stations reporting after 11pm.  

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 28   0   0   39  
Summit Lake (1400′) 16   0   0   12  
Alyeska Mid (1700′) 27   0   0   27  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 30*   W*   6*   18*  
Seattle Ridge (2400′) 32   NE   5   19  
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Riding Areas
Updated Mon, December 02nd, 2019

Status of riding areas across the Chugach NF is managed by the Glacier and Seward Ranger Districts, not avalanche center staff. Riding area information is posted as a public service to our users and updated based on snow depth and snow density to prevent resource damage at trailhead locations. Riding area questions contact: mailroom_r10_chugach@fs.fed.us

Area Status Weather & Riding Conditions
Glacier District
Johnson Pass
Closed
Closed.
Placer River
Closed
Closed.
Skookum Drainage
Closed
Closed.
Turnagain Pass
Closed
Closed.
Twentymile
Closed
Closed.
Seward District
Carter Lake
Closed
Closed.
Lost Lake Trail
Closed
Closed.
Primrose Trail
Closed
Closed.
Resurrection Pass Trail
Closed
Closed. Will be open for the 2019/20 season pending adequate snow cover.
Snug Harbor
Closed
Closed.
South Fork Snow River Corridor
Closed
Closed.
Summit Lake
Closed
Closed.

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