CNFAIC LogoCNFAIC Logo

Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Aleph Johnston-Bloom  
Wednesday, January 25th 2017
Created: Jan 25th 4:19 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
Deuter USA
Special Announcement

Dangerous avalanche conditions exist in many area around Southcentral Alaska including the Anchorage Front Range, Hatcher Pass, and Southern Kenai Mountains. 

  • Click HERE for details about a skier triggered avalanche in South Fork Eagle River. 
  • Click HERE for the Hatcher Pass Avalanche Center advisory and HERE for recent snowpack observations.
  • Attention! If heading to the Southern Kenai Mountains, including the Lost Lake zone, this region is out of the advisory area but received 3-5 feet of snow from Saturday's storm that has fallen on a reported thin/weak snowpack. There were several avalanches observed after the storm. 

The Bottom Line

There is a MODERATE avalanche danger in the mountains surrounding Turnagain Pass. Wind slab avalanches around 1-3 feet thick will be possible to trigger above treeline on slopes that were loaded over the past few days. In the lower elevations (below 2,000', such as the Placer Valley area), watch for persistent soft slab avalanches 1-2 feet thick that could release on a layer of buried surface hoar. Watch for changing conditions. If the approaching storm arrives earlier in the day than forecasted the danger could rise to CONSIDERABLE. Watch for the winds ramping up and precipitation intensity increasing.
Expect the danger level to rise to HIGH overnight as a strong storm impacts the advisory area. 

Practice safe travel protocols, always carry rescue gear and please let us know what you see out there!!! 

Girdwood Valley: Slabs have the potential to be larger due to more snow that has fallen on a weaker snowpack compared to Turnagain Pass. Avalanches are running to the ground.  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!!! Also heads up for roof avalanches as rising temperatures will make these unsupported slopes unstable.

Placer Valley: In the lower elevations (below 2,000’) watch for persistent soft slab avalanches up to 2 feet thick that could release on a layer of buried surface hoar. 

Summit Lake: Rising temperatures, recent snowfall and a generally weaker snowpack has the potential for dangerous avalanche conditions. Please check out the Saturday Summit Summary HERE


Primary Concern

Monday Northeast winds on Sunburst weather station recorded sustained 30-40 mph winds with gusts in the mid 70’s mph. These strong Easterly ridge top winds combined with 8” of new snow have loaded leeward slopes in the Alpine. There was also plenty of snow available for transport and these wind slabs have the potential to be 1-3’ thick on leeward features. In many places in the alpine these wind slabs are resting on old hard wind crust from the wind event prior to this weekend’s storm. This combination was found in steep terrain in the upper elevations over the weekend where several skier triggered avalanche occured. Today it will be best to avoid loaded slopes steeper than 35 degrees where it will be possible to trigger a wind slab avalanche. Look for areas of pillowed or drifted snow and avoid cornices. Feel for hollow feeling snow, stiffer snow over softer snow or slab sitting on hard snow and watch for cracks that shoot out from your snowmachine, skis or board. 

 

 


Secondary Concern

A variety of persistent weak layers exist within the snowpack and vary across our region. In the core Turnagain pass terrain these layers have been generally dormant. However Girdwood Valley had a significant natural cycle Monday night that was observed yesterday. Large avalanches are running on basal facets and sliding to the ground. Slopes around Girdwood that have not slid are suspect for human triggering today.

Throughout the advisory area we are concerned about loading these older layers. In parts of the terrain where the snowpack is shallow there are developed basal facets and in many locations there is a mid-pack layer of facets from December. At the lower elevations, below 2,000', a layer of buried surface hoar exists under the last two snowfall events (1.5-2 feet below the surface). Slab avalanches failing on this layer are possible today where the snow on top is stiff enough to form a slab. Warming temperatures and settling snow have made this the slab more cohesive increasing the potential for a large more connected slab. Observers reported whumpfs on this layer of buried surface hoar at lower elevations yesterday. The lower terrain in Placer Valley is an area where it is possible to trigger a persistent slab avalanche on this layer. All of these weak layers are important to remember as we anticipate receiving a significant load of snow or rain tonight (elevation dependant) into tomorrow!!!

Natural slab avalanche on Penguin Ridge. Photo: Heather Thamm


Additional Concern

Roof avalanches: Heads up near buildings with loaded roof tops as warming temperatures and possible rain today through Friday will make these unsupported slopes unstable. Many roofs have 2-3’ of heavy dense snow from the last few weeks, which is plenty of snow to bury a child, pet or seriously injure an adult. 


Mountain Weather

Yesterday was mostly cloudy with periods of clearing and good visibility. Temperatures were in the 20Fs at ridge tops and 30Fs in the valleys. A few snowflakes fell in the mountains and some sprinkles of rain below 700'. Winds averaged 10-20 with a few gusts into the 30s in the afternoon. 

Today will be mostly cloudy with snow showers throughout the day. There is a small system moving through in advance of a much larger system that is on track to impact the area tonight into tomorrow. 2-6" of snow is forecasted to fall today. Winds will be easterly 15-25 today with gusts into the 30s. Tonight winds are forecasted to increase with gusts into the 70s. Temperatures will be in the 30s and are expected to increase as warm moist air and winds move into the region. Precipitation will be a mixture of rain and snow depending on elevation. There is still some uncertainty about rain/snow line in this system. Expect periods of heavy precipitation intensity overnight. Snow totals will depend on temperatures but 2" of water is predicted by tomorrow morning. The storm will continue into the day tomorrow and there is an unsettled weather pattern into the weekend. 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 34   0  0 50 
Summit Lake (1400') 30  0  0   23
Alyeska Mid (1700')  31  2  .2 49 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812')  23 ENE   14 39 
Seattle Ridge(2400')  25 SE  13  22 

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: Apr 28, 2017 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: Closed
Placer River: Closed
Skookum Drainage: ClosedSKOOKUM DRAINAGE CLOSED TO MOTORIZED USE ON APRIL 1 annually as per the Chugach National Forest Plan document.
Turnagain Pass: OpenOpen thru May 14th.
Twentymile: Closed
Seward District
Carter Lake: OpenClosed May 1.
Lost Lake Trail: OpenClosed May 1.
Primrose Trail: OpenClosed May 1.
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: OpenClosed May 1.
South Fork Snow River Corridor: OpenClosed May 1.
Summit Lake: OpenClosed May 1.

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.
FCNFAIC