Turnagain Pass Avalanche Forecast RSS

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Thu, January 5th, 2017 - 7:00AM
Expires
Fri, January 6th, 2017 - 7:00AM
Forecaster
Heather Thamm
The Bottom Line

A MODERATE avalanche danger remains in the alpine (all areas above the trees) where triggering a small isolated wind slab is possible today. Triggering a deeper 2+’ thick hard slab will be stubborn to trigger, but not impossible on specific terrain features on North and East aspects that have not avalanched yet. Avoid slopes that have existing glide cracks, these could release to the ground without warning.  Within the trees and at lower elevations there is LOW avalanche danger, where triggering an avalanche is unlikely.

***Today’s cold temps and high winds are going to make travel uncomfortable in the upper elevations; windchill factors could be well below zero. Should you decide to venture into the mountains bring extra warm layers and food. Be sure to practice safe travel protocols by only exposing one person at a time in avalanche terrain and watch your partners from a safe zone. This is not a good day to get injured in the backcountry.

In the periphery zones of Girdwood, Johnson Pass and Summit Lake a much shallower snowpack exists and it may be easier to trigger a slab avalanche in these areas.   Check out the Summit Lake Summary  HERE and recent observations from Girdwood HERE.

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Thu, January 5th, 2017
Alpine
Above 2,500'
Moderate (2)
Avalanche risk
Treeline
1,000'-2,500'
Low (1)
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
Low (1)
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

Today Northwest winds are expected to build this morning, 25-45mph in alpine and gusts in the 60’s mph. By late afternoon gusts could reach 75’s mph. Upper Northwest winds in and around Turnagain Pass can be confusing and can funnel through terrain in a more Southwest direction. Luckily there isn’t much snow available for transport in the upper elevations of Turnagain Pass. The December 30th wind event did a pretty good job of hardening the existing surface. With that said there are still some pockets of soft snow that could be blown around and form small fresh wind slabs today. The places to avoid will be steep exposed terrain where getting knocked off your feet will have high consequences. Also if winds do blow from a more SW direction it may make it easier to trigger and older wind slab 4-10” thick on North and East aspects. Watch for blowing snow along ridgtops and cracking will be an obvious sign these windslab are unstable. It is also possible that a small wind slab could step down into an older deeper layer of the snow pack in certain areas. More details on this in secondary concerns.  

Current surface conditions in the alpine are variable with some pockets of soft snow, but there is not a lot available for transport. Photo taken 1/4/17 on a SW aspect of Tincan.

 

Avalanche Problem 2
  • 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

Be skeptical of steep loaded (Northern and Eastern) slopes that haven’t avalanched yet. Likely trigger spots will be in thinner areas of the snowpack near rocks or unsupported slopes that may harbor just the right set-up. A 2-3 foot hard slab is sitting on top of very weak snow (facets and buried surface hoar) in these specific areas that haven’t avalanched. A persistent hard slab avalanche could be triggered near ridge tops or mid slope. Obvious signs like cracking and ‘wumpfing’ are becoming less common in the Turnagain Pass area and may not be an early warning sign. This problem will be stubborn to trigger, but should you find the right spot the consequence could be very dangerous. As you travel today identify Northern and Eastern aspects that haven’t avalanched. Old debris is still very visible and is a good way to identify if a slope has avalanched or not.

In the periphery areas (Girdwood, Johnson/Lynx Creek and Summit Lake) where a thinner snowpack exists several observers have experienced collapsing/wumpfing in recent days. Including a recent snowmachine triggered slab in Lynx Creek  and widespread collapsing and shooting cracks on Notch Mountain in Girdwood Valley two days ago. It will be in these areas where a persistent slab may be easier trigger.

 

Poor structure (hard 2-3′ slab sitting on weak facets) was found yesterday on a loaded North aspect of Tincan and remains a concern on loaded North and East aspects. 

 

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

Over the last two days 3 glide cracks have avalanched in Turnagain Pass; one on a SE aspect of Lynx Creek, SE aspect of Seattle Creek, and the SW face of Eddies. Glide cracks release without any warning and are not associated with human triggers. It is best to avoid existing cracks by not traveling under or within the runout of these unpredictable hazards. Should one avalanche this is the entire snowpack releasing to the ground. 

 

Weather
Thu, January 5th, 2017

Yesterday skies were sunny becoming partly cloudy in the afternoon. Winds began to increase from the NW averaging 10-15mph.   A large temperature inversion began to narrow; ridgetops temps dropped from the low 30F’s to the low 20F’s.   Valley bottom temps increased from 5F to 15F overnight. No precipitation has been recorded in the last week. A dense valley fog has been sitting in and along Turnagain Arm for many days.  

Today expect temperatures to slowly drop throughout 10-15F by late afternoon. Moderate Northwest ridge top wind are expected to build by early afternoon becoming strong (25-45mph) with possible gusts in the 60’s mph.   By early evening gusts could reach 75mph. This could bring the windchill factor well below zero (F) today.

A high pressure system is positioned over Southcentral and Interior, Alaska that will keep temperatures cool and skies clear over the coming days. Winds are expected to decrease by tomorrow afternoon in the Turnagain Pass area, and temperatures will continue to drop possible reaching single digits (F.) This pattern is expected to continue through the weekend into early next week.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 24   0   0   36  
Summit Lake (1400′)  17 0   0   11  
Alyeska Mid (1700′)  19 0   0   23  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′)  22 WNW   8   27  
Seattle Ridge (2400′) 25   WNW   12   42  
Observations
Recent Observations for Turnagain Pass
Date Region Location
12/10/19 Turnagain Avalanche: Tincan and Sunburst from the air
12/10/19 Turnagain Observation: Tincan
12/08/19 Turnagain Avalanche: Tincan
12/06/19 Turnagain Avalanche: Sunburst
12/04/19 Turnagain Observation: Sunburst
12/03/19 Turnagain Observation: Hippy Bowl
12/01/19 Turnagain Observation: Tincan, All elevations
12/01/19 Turnagain Observation: Tincan
11/30/19 Turnagain Observation: Tincan Treeline Plateau/ Common Bowl/ Ridge
11/29/19 Turnagain Observation: Sunburst Ob #2
Riding Areas
Updated Wed, December 11th, 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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