Turnagain Pass RSS

ARCHIVED - Forecasts expire after 24 hours.
Fri, December 11th, 2015 - 7:00AM
Sat, December 12th, 2015 - 7:00AM
Heather Thamm
Avalanche risk The Bottom Line

Today a CONSIDERABLE avalanche danger exists in the Alpine and at Treeline.  Triggering a slab 2-3′ thick will be likely in steep terrain as additional loading will be adding stress to the snowpack.  If venturing into the mountains cautious route-finding and conservative decision-making are essential.

*On the Southern end of Turnagain Pass and near Summit Lake, slab depths are shallower, but triggering a slab 1-2′ thick is likely in avalanche terrain.

Below Treeline a MODERATE avalanche danger exists where an avalanche from above in steep channeled terrain is unlikely, but possible.

Fri, December 11th, 2015
Above 2,500'
3 - Considerable
Avalanche risk
3 - Considerable
Avalanche risk
Below Treeline
Below 1,000'
2 - Moderate
Avalanche risk
0 - No Rating
1 - Low
2 - Moderate
3 - Considerable
4 - High
5 - Extreme
Avalanche risk Avalanche risk Avalanche risk Avalanche risk Avalanche risk
Travel Advice Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features. Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern. Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding, and conservative decision-making essential. Very dangerous avalanche conditions. Travel in avalanche terrain not recommended. Extraordinarily dangerous avalanche conditions. Avoid all avalanche terrain.
Likelihood of Avalanches Natural and human-triggered avalanches unlikely. Natural avalanches unlikely; human-triggered avalanches possible. Natural avalanches possible; human-triggered avalanches likely. Natural avalanches likely; human-triggered avalanches very likely. Natural and human-triggered avalanches certain.
Avalanche Size and Distribution Small avalanches in isolated areas or extreme terrain. Small avalanches in specific areas; or large avalanches in isolated areas. Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas. Large avalanches in many areas; or very large avalanches in specific areas. Very large avalanches in many areas.
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

This morning snow showers combined with moderate winds are expected to bring another 5-7” of new snow to an already precarious snowpack. Yesterday 20″ of unconsolidated new snow was observed above 2000′ on Tincan Mountain. Unfortunately the additional snow today might not be enough to tip the balance naturally. However triggering a slab up to 3’ thick should be at the forefront of our minds as Easterly winds, 20-30mph will be transporting snow and creating more of a cohesive slab.




Yesterday’s Mid Elevation Storm Totals:

  • Girdwood ~9”
  • Northside of Turnigain ~13”
  • Southside of Turnigain ~3”
  • Summit Lake: ~3”

This set up will likely be more dangerous in the Alpine of Girdwood and the Northern side of Turnagain Pass where snow totals yesterday were much deeper. This does not mean triggering an avalanche in a shallower snowpack will be any less likely.Yesterday a D-2, natural slab avalanche was reported in Summit Lake on Butch Mountain and poor structure exists in all areas of our forecast zone. Pay attention for wind loading, shooting cracks, and “wumpfing” if you decide to go into the mountains. Avoiding avalanche terrain is recommended as more snow is expected to fall through out the weekend. Give this snowpack time to adjust and avoid slopes angles over 35°. 

Its always important to watch for deteriorating conditions. Should snowfall become intense or winds become stronger than forecasted, avalanche danger could increase beyond a CONSIDERABLE danger rating. 

Yesterday Tincan recieved an unexpected 20″ of new snow compared to smaller amounts on the Sourthern end of Turnagain Pass

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

It’s important to note the current snowpack structure we are dealing with. A persistent weak layer of faceted snow is sitting on a firm bed-surface below yesterday’s storm totals. Observations yesterday confirm that this new snow was warm and wet below 1500’, but in the upper elevations it was dryer and unconsolidated. As this new snow begins to settle it will likely become more cohesive and “slab like” in the upper elevations. Additional loading due to wind and new snow will increase this process over the next few days. Warm temperatures can also cause a slab to become more cohesive. The scary part about this current set-up is that incremental loading will likely not tip the balance, leaving the slopes primed for a human trigger. The current forecast for today is an additional 5-7” of new snow and more snow forecasted through the weekend. Patience and avoiding avalanche terrain will be the key to not triggering an avalanche while this snowpack adjusts to its new load. 


Fri, December 11th, 2015

Yesterday 20 € of new snow was observed in the upper elevations of Turnagain Pass. This snow favored the Northern side of the pass and arrived with warm temperatures. Rain/snow line was around 1000′ leaving heavy wet snow along the Turnagain Pass road corridor. Winds were light to moderate from the NE.

Overnight skies cleared and temperatures dropped into the upper 20F’s. No new snow was recorded overnight and winds were light 10-15mph from the Northeast.

5-7 € of new snow is expected to arrive late morning. Easterly winds have already picked up this morning and will remain moderate, 15-30mph with Gusts in the 40 through early evening. Temps will be slightly cooler today with rain/snow line estimated for about 500′.

Snow showers and moderate winds are expected throughout the weekend.  

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 29F   3   0.3   36  
Summit Lake (1400′) 27F   1   0.1    12
Alyeska Mid (1700′) 30F   1   0.08    25

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 23F   NE   14   46  
Seattle Ridge (2400′) 25F   E   11   25  
Recent Observations for Turnagain Pass
Date Region Location
05/13/24 Turnagain Observation: Eddie’s, Sunburst, Seattle, Cornbiscuit, Pete’s South
05/13/24 Turnagain Observation: Turnagain Pass non-motorized side
05/12/24 Turnagain Observation: Warm up Bowl
05/07/24 Turnagain Observation: Turnagain Pass Wet Slabs
04/29/24 Turnagain Avalanche: Turnagain aerial obs
04/27/24 Turnagain Observation: Johnson Pass
04/23/24 Turnagain Observation: Turnagain Sunny Side
04/21/24 Turnagain Observation: Bertha Creek
04/20/24 Turnagain Avalanche: Spokane Creek
04/16/24 Turnagain Observation: Cornbiscuit
Riding Areas

The riding areas page has moved. Please click here & update your bookmarks.

Subscribe to Turnagain Pass
Avalanche Forecast by Email

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.