Turnagain Pass Avalanche Forecast RSS

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Tue, December 22nd, 2015 - 7:00AM
Expires
Wed, December 23rd, 2015 - 7:00AM
Forecaster
Graham Predeger
The Bottom Line

The avalanche danger is MODERATE at and above treeline in the backcountry surrounding Turnagain pass.   Pockets of lingering wind slabs 1-3′ deep will be possible to trigger after a quick but intense storm dropped 2+ feet of snow on Saturday in the core advisory area.   Obvious red flags may be absent today as wind slabs are overlain by 1-2′ of soft, unconsolidated snow in many areas.   Additional avalanche concerns today include loose snow, cornices and glide cracks.  

Below treeline the danger is LOW where there has been less snow and less wind.    

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Tue, December 22nd, 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

A skier-triggered avalanche reported yesterday and a snowmachine-triggered avalanche on Sunday point toward a snowpack that still warrants caution and respect.  Wind slabs 1-3’ in depth that formed early in this last storm cycle (Saturday Dec. 19th) resting on weak snow from early December are the suspected culprits.  As winds died down on Saturday afternoon with the storm, these slabs are masked below 6-18” of soft, surface snow in places.  With a lot of traffic in the backcountry over the last 2 days and good visibility (to view lots of terrain), this doesn’t appear to be a widespread problem; rather it’s pockets of instabilities waiting for a trigger.  With this kind of avalanche problem safe travel practices will again be a key way to manage any uncertainties as we move in to a period of high pressure.  Watching your partners, having an escape route planned, grouping up in safe zones and carry and know how to use your avalanche rescue gear will be paramount for a safe holiday season in the backcountry.

We still lack information from the periphery areas such as the Girdwood Valley, Summit Lake and now Johnson Pass/ Lynx Creek (open to snowmachines today).  Generally these areas have a shallower snowpack than Turnagain pass and can potentially harbor more weak snow.  If you are out and about in these zones today please consider submitting a quick observation or even just a photo or two here.

Close-up look at the crown face of a snowmachine-triggered wind slab avalanche from Sunday.  More details here.

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

For folks pushing in to steeper terrain today, you can expect to deal with fast moving, low to medium volume loose snow avalanches (sluffing).  As temps drop and the surface becomes more unconsolidated, these will grow in size.  Usually manageable if anticipated, this is an avalanche problem that can knock a skier off their feet in steep, unforgiving terrain but is unlikely to bury a person. 

                               Lots of loose snow sluffing initiated by skiers can be seen in the fading solstice light yesterday on Widow Maker.  

 

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! There are at least a couple of suspected cornice failures yesterday both on the Tincan ridge and the Sunburst ridge, likely from folks simply walking too close to the edge. 

Glide cracks: Really, glide cracks??  We observed a new (in the last few days) glide crack opening up looker left of Widow Maker on the back side of Seattle ridge.  As with cornices, give these features a wide berth as they are akin to the really drunk guy at the holiday party: Unpredictable!

                             Recent glide crack observed on the backside of Seattle ridge in Main bowl.

Weather
Tue, December 22nd, 2015

Valley fog lifted early giving way to high clouds and mostly sunny skies by yesterday’s solstice sunset (3:42PM).   Winds were light and variable with temps comfortably in the teens.

Along with a 2 second increase in daylight today, we can expect almost a carbon copy of yesterday’s weather.  Valley fog should burn off rather quickly with light winds from the NW in the 5-15mph range.  Temperatures will be in the teens at ridgetop locations and slightly cooler (single digits) in cold sink areas such as Summit Lake and Granite campground area.  No new precipitation is expected today.

Looking out a few days, souchcentral AK will be under high pressure (cold and clear) at least through Christmas eve with a chance of unsettled weather moving into the region on Christmas day.  

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 16    0 0    53
Summit Lake (1400′) 4   0   0   18  
Alyeska Mid (1700′) 18   0   0   36  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 15  variable 3* 10*  
Seattle Ridge (2400′) 15   NW*   3*  15*

*Both weather stations had periods of inoperable wind data yesterday.

Observations
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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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