Turnagain Pass Avalanche Forecast RSS

Archives
ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Tue, December 11th, 2018 - 7:00AM
Expires
Wed, December 12th, 2018 - 7:00AM
Forecaster
Aleph Johnston-Bloom
The Bottom Line

The avalanche danger is  MODERATE  above 2500′ in the Alpine. Watch for wind slabs in steep, wind-loaded start zones. Triggering a slab avalanche is still possible. As new snow accumulates assess how well it bonds to the snow surface below.   Pay attention to changing conditions.  

SUMMIT LAKE:    A weak and  shallow snowpack exists  under the recent storm snow. Slab avalanches 1-2′ deep may to be easy to trigger on steeper slopes.

 

Thanks to our sponsors!
Tue, December 11th, 2018
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
  • Almost Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic
    Very Large
    Large
    Small
    Size
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.

Likelihood of Avalanches
This graphic depicts how likely you are to trigger avalanches or encounter natural avalanches while traveling on avalanche prone slopes. Unlikely means that few avalanches could be triggered in avalanche terrain and natural avalanches are not expected. The chance of triggering or observing avalanches increases as we move up the scale. Certain means that humans will be able to trigger avalanches on many slopes, and natural avalanches should be expected.

Size of Avalanches
This graphic depicts the potential size and destructive force of expected avalanches. Small avalanches are not large enough to bury humans and are relatively harmless unless they carry people over cliffs or through trees or rocks. Moving up the scale, avalanches become large enough to bury, injure, or kill people, large enough to bury or destroy vehicles and break a few trees, and large enough to destroy railway cars, buildings, or a substantial amount of forest. Historic avalanches are massive events capable of destroying villages and gouging or altering the landscape.
More info at Avalanche.org

Leeward, steep, unsupported slopes above 2500′ may still harbor wind slabs today from the winds Sunday night/Monday morning. Look and feel for stiff, pillowed snow and cracking and listen for hollow, drum-like sounds. Loading patterns can be very localized and it may be hard to tell where the wind effect is with the few inches that fell yesterday and overnight. Another 2-5″ is forecast to fall today. 

Additionally, pay attention to how new snow falling today bonds to the snow below. As the inches slowly stack up over the hard wind-blown snow surface or over the melt-freeze crust at lower elevations loose snow avalanches may be a possibility in steep terrain. If the snow is cohesive enough shallow storm slabs may form. Hand pits and small tests slopes will be useful ways to assess bonding.  

Wind effect in Tincan Common, 12-9-18

Additional Concern
  • 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

As is often the case we are concerned with the snowpack in the periphery zones of our advisory area, Crow Pass and Summit Lake.  Where the Alpine snowpack is shallower, the potential to trigger a persistent slab avalanche on weak snow near the ground increases. Observations prior to the storm showed weak facets near the ground in Summit Lake. We have limited information from north of Girdwood but suspect a weak set-up.  If traveling to these areas the possibility of triggering a dangerous avalanche remains. Choose terrain carefully.

 

Red flags to watch for:

  • Recent avalanches 
  • Whumpfing (collapsing) of the snowpack, a sign to avoid avalanche terrain.
  • Shooting cracks, likely to be seen near ridgelines where the wind has formed wind slabs.

Tenderfoot, 12-5-18 

Weather
Tue, December 11th, 2018

Yesterday:  Skies were cloudy with snow showers throughout the day. Temperatures were in the 20Fs to low 30Fs. Winds were easterly 5-15 mph with gusts into the 30s. Snow showers continued overnight, winds were light and temperatures dropped a few degrees.  

Today:  Snow showers continue with 2-5″ forecast to fall today with an additional 2-6″ tonight. Temperatures will start in the mid to high 20Fs and drop slowly throughout the day into the low 20Fs and teens tonight. Winds will be variable and light.  

Tomorrow:  Snow showers and cooler temperatures are the trend for the week. Thursday may see a brief window of clearing. The pattern remains active into the weekend. Stay tuned as we watch storm tracks and temperatures!  

*Seattle Ridge anemometer (wind sensor) is rimed over and not reporting.  

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′)  29     4    0.4     29  
Summit Lake (1400′)  27      1     0.1   5  
Alyeska Mid (1700′) 28   3   0.3   12

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 21    NE 9    36
Seattle Ridge (2400′) 25   *no data   *no data     *no data    
Observations
Recent Observations for Turnagain Pass
Date Region Location
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
11/29/19 Turnagain Observation: Sunburst Ob #1
11/27/19 Turnagain Observation: Tincan
11/25/19 Turnagain Observation: Sunnyside
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.

Subscribe to Turnagain Pass
Avalanche Forecast by Email