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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Mon, December 21st, 2015 - 7:00AM
Expires
Tue, December 22nd, 2015 - 7:00AM
Forecaster
Wendy Wagner
The Bottom Line

A MODERATE avalanche danger exists in the backcountry surrounding the Turnagain Pass region. Today is the second day after a 15-25+ inch storm and although signs are pointing to a stabilizing snowpack, we are still within the window for possible human triggered slab avalanches. These are most likely to be found on windloaded slopes at, or above, treeline (see below for a slab triggered yesterday). Slabs may vary in thickness from 1-3+ feet and could break above you. Always watch your partners closely and expose only one person at a time in avalanche terrain.

*There is little information about the periphery zones such as the upper elevations of Girdwood Valley, Portage Valley and Summit Lake on the Kenai. Danger in these areas could be higher than Turnagain Pass itself.

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Mon, December 21st, 2015
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
  • 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

Yesterday was the first clear day after a quick hitting storm dropped over 2′ of snow on the North side of Turnagain Pass, lesser amounts were seen in Girdwood Valley and the South side of the Pass. Many folks were out enjoying the new snow and easing onto steeper slopes and into avalanche terrain. Despite the number of people out and about, we only had a report of one human triggered slab avalanche. This slide was triggered by a snowmachiner on the front side of Seattle Ridge (Easterly aspect ~2,200′, photos below). This slope is not especially steep, but it is on the North side of the Pass and in an area that typically sees larger snowfall amounts. More on the report HERE. Check out additional reports sent into us from Eddies, Tincan and Sunburst HERE.

If you are headed out today, remember we are still close enough to the storm that lingering wind slabs may remain sensitive to human triggers. Watch for areas with stiffer snow over softer snow and hollow feeling snow. Also look for patterns of wind loading on leeward and cross loaded slopes (35 degrees and steeper).

*Don’t forget your safe travel practices, especially considering there are very few ‘obvious signs of instability’ currently. As a reminder these signs are: recent avalanches, shooting cracks, whumphing and rapid changes in weather. Safe travel practices include: Watching your partners, having an escape route planned, grouping up in safe zones and carrying (and knowing how to use) your rescue gear in the event a person is buried.

The cooler temperatures are helping stabilize the slab avalanche potential by loosening the snow surface, but this will also contribute to larger loose snow avalanches (sluffs). Hence, keep an eye on your sluff.

 Photos above are of a snowmachine triggered slab avalanche triggered yesterday. Rider was able to throttle out. (Thanks to Chad Winberg for sending in these photos).

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

Cornices have grown a fair bit from Saturday’s storm. As we enter a several day stretch of mostly clear weather and folks are traveling further into the backcountry, don’t forget to give these features a wide berth! 

The photo below illustrates the cornice that forms at the head of Zero Bowl (Mama’s Bowl) on the backside of Seattle Ridge. This cornice, like many others, can grow larger than many greyhound buses lined up end to end. Notice the snowmachine tracks traveling along the ridge just shy of the cornice. It can often be hard to determine how far a cornice extends when approaching from the wind ward side.

 

Weather
Mon, December 21st, 2015

Mostly sunny skies with valley fog covered the region yesterday. Winds have been light from a generally Westerly direction for the past 24-hours and temperatures continue to decrease  under the clear skies.

Today, we should have mostly clear skies as we are sitting between storm systems. Cooler air continues to stream in from the West and there is a slight inversion this morning; temperatures are in the 5-10F range at the road elevation and ~15F on the ridgetops. Winds are expected to remain light and variable today.

For tomorrow, Tuesday, mostly clear skies are on tap with winds turning to the West. The winds should stay light but may pick up to the 10-15mph range. It looks as though we are in this cold and clear spell to around Christmas day.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 18   0    0 58  
Summit Lake (1400′) 10   0    0 18  
Alyeska Mid (1700′) 21   0     0   38  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 18    W 4   11  
Seattle Ridge (2400′) 19    N/A  N/A    N/A  
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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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