Turnagain Pass RSS

Archives
ARCHIVED - Forecasts expire after 24 hours.
Issued
Tue, January 17th, 2017 - 7:00AM
Expires
Wed, January 18th, 2017 - 7:00AM
Forecaster
Heather Thamm
Avalanche risk The Bottom Line

The avalanche danger is MODERATE today in the mountains surrounding Turnagain Pass at all elevations and on all aspects. Loose snow avalanches are likely on steep terrain and could be fast moving and run further than expected. Triggering a soft wind slab 1-2′ thick is possible on steep terrain features and on unsupported slopes that have been loaded by winds. Northern aspects in Turnagain Pass are also suspect of deeper instabilities where a triggering a slab 2+’ thick is also possible.  

***In the Girdwood Valley where 2.5′-3′ of snow fell this weekend, twice as much as Turnagain Pass, heighten avalanche conditions exist. Careful snowpack evaluation, cautious route-finding and conservative decision making are essential today if venturing into this area. It will be important to keep slope angles less than 35 degrees and avoid being under big runout zones. Triggering a slab 3′ thick or deeper is more likely in Girdwood and should warrant extra caution!!!

Special Announcements
  • Placer area will open to Motorized use on Wednesday (1/18). The Forest Service is working to get the 20-Mile snow corridor established and opened ASAP.   Please reference the bottom of this page for the latest snowmachine area openings on the Chugach NF.  

  • Lost Lake and Primrose are now open for snowmachining!  Please STAY ON existing and hardened trail surface through the lower sections of this route.

  • Dangerous avalanche conditions exist in Hatcher Pass. Click  HERE  for a winter weather advisory update yesterday by the Hatcher Pass Avalanche Center and more details about their snowpack from the weekend.  
  • Join CNFAIC for our final Fireside Chat on Thursday night, Jan 19th! Aleph Johnston-Bloom will discuss “how has the Turnagain Pass snowpack shaped up” and more – Details  HERE.
Tue, January 17th, 2017
Alpine
Above 2,500'
2 - Moderate
Avalanche risk
Treeline
1,000'-2,500'
2 - Moderate
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

Storm totals (Jan.13th – Jan.16th) 

  • Turnagain Pass = 15” (1.1” H20)
  • Girdwood = 30” (2.3” H20)
  • Summit Lake = 7” (0.6” H20)

Two snow storms over the weekend brought significant snowfall to our region. Girdwood received about 30” total and Turnagain only 15”.  Moderate Easterly winds occurred during the first storm and blowing snow was observed during the early part of the the second event. Observers over the weekend reported good bonding in the popular areas of Tincan trees and SW shoulder of Sunburst. Due to limited visibility there is not much information from the alpine as to how well this snow has bonded to harder surfaces below. Expect Western (SW – NW aspects) to be more top loaded or cross loaded from the first storm event. Since most of the snowfall arrived yesterday without much wind previous loading patterns may be challenging to indentify. Should winds unexpectedly increase today there is a lot of snow available for transport and fresh wind slabs could be very tender. 

Be on the lookout for obvious clues like recent avalanches, shooting cracks and blowing snow. Evaluate the snow as you travel by jumping/riding over small test slopes and looking for places where the snow feels stiffer and more affected by winds. 

In Girdwood wind slabs may be closer to 3’ thick and could be more tender due to higher snowfall totals and more stress on the snowpack. More caution is advised in this area and it is best to avoid slopes steeper than 35 degrees. 

A photo of the loading patterns on the SW aspect of Tincan Proper from Saturday afternon, Jan.14th, following the first snow storm that left up to 12″ in the upper elevations of Turnagain Pass. Photo by Andy Moderow

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

Yesterday 7” of new snow fell in Turnagain Pass, 13” fell in Girdwood, all without much wind. Snow totals could be deeper in the alpine and triggering a loose snow avalanche will be likely on steeper slopes. Fast moving “sluff” could entrain snow, run further than expected and easily knock you off your feet. Manage this problem by letting the snow move past you and choose terrain that doesn’t have high consequences if you fall. Although it is unlikely to bury a person, keep in mind that larger terrain will have more volume. Cold temperatures could increase this problem today.

 

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

A variety of weak layers exist with in the snowpack and vary across our region. In the heart of our forecast zone,Turnagain Pass, Northern aspects are the most suspect. On the Southern end of Turnagain Pass towards Johnson Pass many aspects have a shallow snowpack, and may harbor more suprises. It will be in these location where triggering a slab on an older layer (facets or buried surface hoar) is possible. In Girdwood where twice as much snow fell and limited snowpack information exists, triggering a deeper more high consequence avalanche is more likely. Should you see recent avalanche activity, experience shooting cracks, or “wumpfing” these are obvious clues that the snowpack is unstable. 

In the lower elevations below 1500’ where a layer of surface hoar was buried by this last storm event, it may be possible to trigger a soft slab on steep unsupported terrain features or along steep gully’s. For today this problem is more of a concern below treeline in places like Portage or Placer Valley. Ice climbers and hikers should be aware of the terrain above, and avoid being in the run-out of large steep slopes. Observers yesterday mentioned that snow drifts near Portage Lake were up to 2’ deep. 

A photo of shooting cracks following a large collapse “wumpf” at about 1800′ an a NE aspect of Raggedtop, Girdwood Valley, following the end of the first storm on Saturday afternoon. 

Weather
Tue, January 17th, 2017

Early yesterday morning snow started falling and by late morning 7 € (17cm) was recorded at the Tincan Beaded Stream station. This snow came in with light NW winds and temperatures were in the low teens F. In Girdwood 13 € of new snow was recorded.  Overnight skies cleared and temperatures dropped to about 0F. Winds have remained light from the West. No precip was recorded overnight.

Today cold arctic air has moved into Southcentral, Alaska and temperatures are expected to remain just below zero today. Winds are forecasted to remain light from the NW and skies are expected to be mostly clear.  

A high pressure system over Interior Alaska is expected to impact Southcentral throughout the week keeping temperatures below zero for next next few days. Skies will be clear, but Northwest winds could pick up tomorrow with ridgetops near 20mph.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 9   1   .1   45  
Summit Lake (1400′) 5   0   0   14  
Alyeska Mid (1700′) 9   3   .26   45  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′)  2 W   3   10  
Seattle Ridge (2400′) 4    rimed rimed   rimed  
Observations
Recent Observations for Turnagain Pass
Date Region Location
03/28/24 Turnagain Observation: Sunburst
03/27/24 Turnagain Observation: Tincan Trees
03/26/24 Turnagain Observation: Cornbiscuit
03/25/24 Turnagain Observation: Tincan
03/22/24 Turnagain Avalanche: Magnum Northwest Aspect
03/21/24 Turnagain Observation: Sunburst
03/21/24 Turnagain Observation: Tincan Proper North Aspect
03/20/24 Turnagain Avalanche: Seattle Creek Drainage
03/19/24 Turnagain Observation: Tincan CFR
03/18/24 Turnagain Avalanche: Tincan – Eddies – Seattle Ridge
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.