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Turnagain Pass Avalanche Forecast RSS

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Fri, December 12th, 2014 - 7:00AM
Expires
Sat, December 13th, 2014 - 7:00AM
Forecaster
Graham Predeger
The Bottom Line

The avalanche danger is LOW today across the forecast zone.   Our snowpack has had 3 days to adjust to the warm, wet storm earlier in the week.  Recent cooler temperatures have acted to lock the snowpack up tight at mid elevations around treeline. In the upper elevations (above ~2,500′) the snowpack is exhibiting good strength, low potential for avalanches to propagate and a good structure with the lack of a  persistent weak layer. Human-triggered avalanches will be unlikely today though LOW danger does not mean NO danger.  

Concerns today will come in the form of all the other hazards associated with backcountry travel right now.   This includes cornices, glide cracks and early season hazards such as rocks, stumps, open water, etc.

Below treeline (1,500 and lower) there is not enough snow cover for avalanches to be of concern.

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Fri, December 12th, 2014
Alpine
Above 2,500'
Low (1)
Avalanche risk
Treeline
1,000'-2,500'
Low (1)
Avalanche risk
Below Treeline
Below 1,000'
No Rating (0)
Avalanche risk
Alpine
Above 2,500'
Avalanche risk
Low (1)
Treeline
1,000'-2,500'
Avalanche risk
Low (1)
Below Treeline
Below 1,000'
Avalanche risk
No Rating (0)
Danger Scale:
No Rating (0)
Low (1)
Moderate (2)
Considerable (3)
High (4)
Extreme (5)
Avalanche Problem 1
  • Normal Caution
    Normal Caution
Normal Caution
Normal Caution means triggering an avalanche is unlikely but not impossible.
More info at Avalanche.org

Snow pit test results and some substantial slope testing are pointing toward a snowpack that is gaining strength and losing energy in the upper elevations as we put time between now and the (Dec. 7-9) warm storm of earlier this week.  Perhaps the most significant slope test in the backcountry yesterday was observed when a large cornice block failed unintentionally landing on a steep (~40 degree) slope pulling out only a small slab.  Without investigating fully, this is where I’d expect to find isolated pockets of stubborn wind slab in the 12″ range.  If entering steep, committing terrain just below ridges today, practice safe travel protocol and good situational awareness identifying both safe zones and escape routes. An avalanche today is unlikely large enough to bury a person but moving snow could be enough to knock you off your skis or sweep you into a terrain trap.

We have observed widespread surface hoar growth throughout the Turnagain zone over the last 2 days.  Though not an issue today, this is sitting on a variety of surface types and could prove problematic if buried in-tact.  We’ll be mapping this layer carefully with subsequent storms.

Early season hazards and a tenacious rain crust in the mid elevations (consistency of skiing over a coral reef) are legitimate concerns and require careful travel in order to avoid injury.  Boot-packing in the 1,000 – 1,500’ elevation band was by far the most hazardous part of our tour yesterday due to ice, early season hazards and a lack of snow.

Avalanche Problem 2
  • 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

My partner and I witnessed 2 separate human triggered cornice failures in a matter of a half hour on the Tin Can ridge leading up to Hippy bowl yesterday.  Cornices in our region are fairly well developed for this early in the season.  Recognize them, and give them an extra WIDE BERTH if travelling on corniced ridges.  This holds true today and always!

                               2 separate cornice failures resulted from skiers traversing the ridge.  Hippy bowl on Tin Can.

Additional Concern
  • Glide Avalanches
    Glide Avalanches
Glide Avalanches
Glide Avalanches are the release of the entire snow cover as a result of gliding over the ground. Glide avalanches can be composed of wet, moist, or almost entirely dry snow. They typically occur in very specific paths, where the slope is steep enough and the ground surface is relatively smooth. They are often proceeded by full depth cracks (glide cracks), though the time between the appearance of a crack and an avalanche can vary between seconds and months. Glide avalanches are unlikely to be triggered by a person, are nearly impossible to forecast, and thus pose a hazard that is extremely difficult to manage.
More info at Avalanche.org

Being nearly impossible to predict or forecast glide avalanche failure, your best bet will be to simply avoid exposure to glide cracks entirely.  This avalanche concern is like a wild Horse; it has the ability to be tame through the entire season and melt out benignly or, release catastrophically without warning unleashing a fury of destruction.

Weather
Fri, December 12th, 2014

The welcomed cooling trend continued yesterday across our region with all the weather stations (except Whittier) reading below freezing temperatures and dipping to the low 20’s F.   A lack of wind allowed a persistent fog bank to embed from the Anchorage bowl down Turnagain arm and south over Turnagain pass.   Just a trace of snow was observed on vehicles in Girdwood yesterday morning, really just precip particles associated with a low fog bank.   Above the fog (roughly 1,900′) the sky was blue, winds were calm and the atmosphere stable.

Weather looks to be quiet again today with weak surface flow likely not pushing the fog out of the region.   It’ll likely be another grey day at sea level but if you are fortunate enough to be in the mountains today, sunshine abounds above the low cloud deck!   We may see a small bump in temperatures to the high 20’s F at 1,000′ with ridgetop winds remaining in the single digits from the east.   No precipitation is expected today.  

Our next best chance for winter-ish weather appears to be tomorrow afternoon and into Sunday with a significant low tracking across the north Pacific today.   There appears to be plenty of moisture associated with this system and temps appear to be hovering right around the freezing mark.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 21   0   .1    18
Summit Lake (1400′)  19 o   o   4  
Alyeska Mid (1700′)  24  0 .1   11.8  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′)  21  W  5  13
Seattle Ridge (2400′)  23 SE    3 9  
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Riding Areas
Updated Mon, October 26th, 2020

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

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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.