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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Heather Thamm  
Tuesday, January 17th 2017
Created: Jan 17th 6:15 am
2 Moderate Alpine / Above 2,500' Travel Advice: Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
2 Moderate Treeline / 1,000'-2,500' Travel Advice: Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
2 Moderate Below Treeline / Below 1,000' Travel Advice: Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
 Show the Complete North American Avalanche Danger Scale
Special Announcement
  • 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.

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!!!


Primary Concern

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


Secondary Concern

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

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. 


Mountain Weather

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') .1  45 
Summit Lake (1400') 14 
Alyeska Mid (1700') .26  45 

 

RIDGETOP 24-hour data (6am - 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812')  2 10 
Seattle Ridge(2400')  rimed rimed  rimed 

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).

Winter snowmachine use open/closed status and riding conditions updates

Riding status is not associated with avalanche danger. An area will be open to motorized use in accordance to the Forest Management Plan when snow coverage is adequate to protect underlying vegetation. Backcountry hazards including avalanche hazard are always present regardless of the open status of motorized use areas.

(Updated: Mar 15, 2017 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: OpenPlease park on road in and leave the turnaround (near outhouse) open for trailers to turn around.
Placer River: Open
Skookum Drainage: OpenSkookum drainage closes to motorized use on April 1 annually as per the Chugach National Forest Plan document.
Turnagain Pass: Open
Twentymile: Open
Seward District
Carter Lake: Open
Lost Lake Trail: OpenPlease STAY ON existing and hardened trail surface through the lower sections of this route.
Primrose Trail: OpenPlease STAY ON existing and hardened trail surface through the lower sections of this route.
Resurrection Pass Trail: ClosedClosed for 2016/17 winter season. This is a non-motorized season. This alternates every other year and will open again during the 2017/18 winter.
Snug Harbor: Open
South Fork Snow River Corridor: Open
Summit Lake: Open

Subscribe to the Turnagain Area Avalanche Advisory:

The information in this advisory is from the U.S. Forest Service, which is solely responsible for its content. This advisory describes general avalanche conditions and local variations always occur. This advisory provided by the Chugach National Forest, in partnership with Friends of the Chugach National Forest Avalanche Information Center.


USFS SNOW AND AVALANCHE HOTLINE (907) 754-2369
If you have comments or questions regarding CNFAIC operations or winter recreation management, please email staff@chugachavalanche.org
© 2017 Chugach National Forest Avalanche Information Center. All rights reserved.
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