Avalanche Advisory

Turnagain Area Avalanche Advisory
Thursday, April 26th 2018 7:00 am by Heather Thamm
ARCHIVED ADVISORY - All advisories expire after 24 hours from the posting date/time.
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The Bottom Line

The avalanche danger is MODERATE, but may increase to CONSIDERABLE if the sun appears this afternoon. Triggering a wet avalanche is possible today on steep slopes below 2500’. If the sun comes out natural wet avalanches are possible in the afternoon in the alpine. It is also possible to trigger a storm slab 1-3’ deep in the alpine where drier snow exists. Cornice fall could trigger a storm slab or wet loose avalanche below.

**In Portage Valley where precipitation totals were much greater this week, be aware of popular hiking areas with avalanche terrain above like Byron Glacier trail. Some hikers last Saturday had a close call when an avalanche released naturally from above. 

Friday outlook: Similar weather is forecasted for tomorrow. Springtime conditions require constant evaluation of the snowpack and flexible objectives. Evaluate terrain and snowpack as you travel. Extra caution if solar radiation starts changing the snow.

 Show the Complete North American Avalanche Danger Scale
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.
Special Announcement
  • CNFAIC is closing up shop and today, April 26, is the final forecast of the season. We do monitor/post any observations that come in all spring and summer - so please keep us, and the community, posted on any snow/avalanche information you may come across on your upcoming adventures! Check back on Saturday, April 28th for springtime tips. 
  • Turnagain Pass, Carter Lake and Snug Harbor remain open. Keep an eye on the riding status at bottom of the page in the coming weeks as the snow continues to melt. 

Avalanche Problem 1

Wet Loose

Almost Certain
Very Likely


Very Large


Triggering a wet avalanche is possible today where rain has saturated the snowpack in the mid and lower elevations. Daytime temperatures are expected to rise into the mid-40F’s in the lower elevations and mid-30F’s to 2500’. Today’s forecast is calling for scattered rain showers (0.15” of rain) below 2300’. As instability showers move through our region, patches of blue sky and sun are also possible at times. Today’s avalanche danger will depend on how warm it gets and if radiation from the sun impacts the snow. Even a little sun shining through thin cloud cover can create rapid warming of the snowpack. Expect surface snow to be wet and ’pushable’ in the mid elevations. Areas like Portage and Girdwood Valley that received more rain in the last few days, there is more potential for a wet avalanche to entrain deeper into the snowpack, and larger avalanches are possible. If the sun heats up dry snow in the upper elevations, natural wet snow avalanches could release naturally, especially near rocks or where chunks of cornice are shedding. Pay attention to how wet and saturated the snow feels. Is this the top 2 or 3” of wet snow or a deeper issue? If your skis or snowmachine start punching deeper into the snowpack, avoid all steep slopes. Triggering a wet avalanche, once it's picked up momentum, can be difficult to manage. 

Water totals (inches of rain) in the last two days. New snow in the upper elevation since Tuesday could range from 1 to 3 feet (Turnagain Pass vs. Girdwood)  

  • Turnagain Pass:   0.5”    (1.6” total since Saturday)  
  • Girdwood Valley:  1.2”    (2.8” total  since Saturday)
  • Portage Valley:     2.4”    (7.4” total since Saturday)
  • Summit Lake:       0.1”    (0.3” total since Saturday)

Slopes above Byron Glacier trail have seen a lot of avalanche activity this week. Note the large cornice that still looms above, and rocks that can easily heat-up and shed snow with daily warming and sun.  


Visibility was limited yesterday, but we did see a few new natural wet loose avalanches on Seattle Ridge. This aspect has seen a lot of wet avalanche activity this season, but it doesn't mean this aspect is done. Human triggered avalanches are still possible. Monitor how wet and saturated the snow is and how it changes throughout the day. 

Avalanche Problem 2

Storm Slabs

Almost Certain
Very Likely


Very Large


If you are heading out to catch new snow at higher elevations, extra caution is warranted where little information exists about how well the snowpack is adjusting. Storm slabs that formed on Tuesday due to heavy snow and strong winds could range from 1 to 3 feet deep depending on what part of the forecast zone you are in. Expect storm slabs to be deeper in Portage Valley and Girdwood. Any sun on solar heating could make them easier to trigger in the afternoon.  Evaluate snow and terrain carefully and ease into steep slopes with caution. Also be aware of slopes that suddenly change from drier snow in the upper elevation to wetter snow mid elevation.  

Upper elevation North aspects: Shaded aspects in the Alpine had a thin layer of facets and/or surface hoar over a crust under last week's new snow. This layer may still be lurking, which could result in slab avalanches 2 - 4+' thick composed of couple of storm layers of snow.   

Additional Concern


Warm and stormy weather this week has caused cornices to shed. There are some places, like Seattle Ridge where Cornices are large and challenging to judge if you are on them. Give them plenty of space and avoid being under cornices. Daily warming and any sun that might appear today will be adding additional stress. 

A brief clearing yesterday afternoon showed recent cornice fall below CFR on Tincan ~2400'.  

Mountain Weather

On Tuesday an impactful storm front moved through our region bringing strong winds, periods of heavy rain and snow to our region. Turnagain Pass remained on the drier side with 0.4” of rain that tapered off Tuesday night and 0.1” was recorded in the last 24 hours. Portage on the other hand had near 2” of rain on Tuesday and additional 0.4” yesterday. Rain/snow line has fluctuated from 500’ to 2000’, but daily warming yesterday showed a period of above freezing temperatures as high as 2400’ on Seattle Ridge.  Winds on Sunburst were Easterly and averaged 24mph with gusts reaching the 90’s mph on Tuesday. Yesterday winds were moderate from the East 15-30mph.  

Mostly cloudy skies and scattered rain showers will continue across our region with up to 0.15” of rain possible. This could be 1-2” of new snow above 2500’. Temperatures could range from the mid-40F’s at sea level to mid-30F’s in the mid elevations. Easterly ridgetop winds are expected to be 10-20mph. 

Tomorrow looks similar with more scattered rain and snow showers on tap. Daily temperatures swings will range from 40F’s during the day to low 30F’s at night near sea level. Cooler temps in the alpine.  Winds will remain moderate from the East. A similar pattern is expected through the weekend. 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 36   0 0.1  65 
Summit Lake (1400') 36  18 
Alyeska Mid (1700') 35  0.03  65 


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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 24  ENE  14  34 
Seattle Ridge(2400') 30  ESE  14   36

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 15, 2019 )

Glacier District
Johnson Pass: ClosedClosed as of 4.3.19
Placer River: ClosedClosed as of 3.20.19 due to lack of snow.
Skookum Drainage: ClosedPlacer access closed as of 3.20.19 due to lack of snow.
Turnagain Pass: Open
Twentymile: ClosedClosed as of 3.20.19 due to lack of snow.
Seward District
Carter Lake: Closed
Lost Lake Trail: ClosedClosed as of 3.22.19 due to lack of snow
Primrose Trail: ClosedClosed as of 4.3.19 due to lack of snow
Resurrection Pass Trail: ClosedClosed for the 2018/19 season. Next season will be open to motorized use.
Snug Harbor: OpenRainbow Lake was still frozen with small patches of melting ice as of Sunday afternoon Apr 14th. Snow is melting fast along the first 1/2 mile of road from trailhead.
South Fork Snow River Corridor: ClosedClosed as of 3.20.19 due to lack of snow.
Summit Lake: Closed

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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.

If you have comments or questions regarding CNFAIC operations or winter recreation management, please email
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