Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Wendy Wagner  
Saturday, November 22nd 2014
Created: Nov 22nd 5:39 am
ARCHIVED ADVISORY - All advisories expire after 24 hours from the posting date/time.
2 Moderate Alpine Travel Advice: Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
2 Moderate Treeline Travel Advice: Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
0 NO RATING Below Treeline
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Broken Tooth Brewing
Special Announcement

Good Morning CNFAIC users!! This is our first advisory for the 2014/15 winter season and we have a couple new items to introduce:

First, we will be issuing danger ratings for three elevations bands - Alpine (above 2,500-3,000'), Treeline (1,500' to 2,500-3,000') and Below Treeline (Below 1,500'). These elevation numbers are not exact since treeline elevations are variable within the region. This expansion will help forecasters, as well as hopefully the public, to better describe and understand the differences in danger and avalanche concerns with respect to elevation.

Second, we have added a new table to the Mountain Weather section, see below.

The Bottom Line

There is a MODERATE avalanche danger for wind slab avalanches at elevations near treeline and in the upper elevation alpine zones. Below treeline a lack of snow cover results in no rating. Wind slabs and cornices have been forming over the past two days and may continue to grow today. These are 4-24" thick (variable) and will be possible to find and trigger on predominantly West and South aspects, although all aspects are suspect. The potential to trigger a wind slab will increase with elevation as the snow becomes drier and slabs need more time to bond. 

The next advisory will be Tuesday morning at 7am. 
Outlook for Sunday and Monday: The weather and resulting avalanche conditions are expected to be very similar for Sunday and into Monday.

Primary Concern

It is a pleasure to report we have had new snow during the past two days! After an onslaught of rain up to 3,500' on Tuesday, temperatures have dropped and Thursday we picked up around 6" above 1,800' with another 2" yesterday - and add to that, another 1-3" possible today. Numbers may be modest and the rain/snow line high, but it's snow nonetheless.

Very strong winds have redistributed the new snow into variable drifts and slabs from a couple inches thick to 3' in some locations. These sit on a uniform rain crust from Tuesday's rain that extends up to 3,000' and likely higher. Hence, the snow surface yesterday was a combination of new snow drifts and slabs with scoured and VERY SLICK rain crust in between. 

For anyone venturing into the backcountry today, watch for current wind loading to increase the sensitivity of wind slabs. Yesterday, slabs were stubborn and showing signs of bonding to the preexisting surface (ice) well, yet this was in one location and is not a certainty. Steeper slopes approaching 40degrees should be approached with extra caution. Any ride, in even a small avalanche, could send you down an icy slope littered with rocks. Beware of the ice under the new snow. Performing hand pits and digging in the new snow to assess the new/old snow interface are good ways to suss out how well the slabs are bonding. Also, keep an eye out for any recent avalanches and cracking in the snow around you.

If you get out this weekend please let us know what you are seeing - pass on a photo or two and/or an observation!!

Below is a classic small cornice break during a period of wind loading (Sunburst 11/21 2,300' SW facing).

A look at the snow line (~1,700')

*High elevations over 4,000': There is much uncertainty as to how much snow has fallen at these high elevations (Raggedtop Mtn for example) and if the faceted weak layer that was reported earlier in November remains under the bulk of the November snow. Under these circumstances, large avalanches are possible. Digging in the snow to assess the snowpack structure is a must if considering travel in these areas.

Secondary Concern

Watch for cornices to break under the weight of a person. Cornice growth has been significant during the past couple days at the high elevation ridgelines. 

Additional Concern

There are still a fair number of glide cracks littered about the mountains at elevations between 2,000-3,500'. Many of these are obscured by the new snow so keep an eye out and steer clear from being under cracks. Although we have seen no new glide avalanche activity for close to a week, these unpredictable avalanches are something to avoid as a general rule.

Mountain Weather

During the past 48-hours we have seen 6-8+ inches of new medium density snow at the mid and upper elevations with rain at the lower elevations. Strong Easterly winds averaging 20-30 mph with gusts in the 50's accompanied the new snow. The rain/snow line has been 1600-1800' after dropping substantially from 3000+' earlier in the week.

Today, an additional 1-3" of snow is possible above 2,000' and rain below. Ridgetop winds have decreased overnight where they are expected to remain, in the 15-25mph with stronger gusts from the East. Temperatures will stay near the mid 30'sF at 1,000' and the mid 20'sF on the ridgelines. Skies should remain mostly cloudy with a few breaks in the clouds through the day.

Sunday and Monday conditions look remarkably similar. A large low pressure system spinning in the Gulf will keep the Eastern Turnagain Arm area under off-and-on snow showers above 1,500-2,000' with 2-5" of snow accumulation each day (.2-.7 rain below 1,500').

Below are our new tables for this season that will spell out the past 24-hour weather data for key weather stations in Turnagain Pass, Summit Lake and Girdwood Valley.
Also, for a better look at November's weather see our monthy chart HERE.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880')  33  1  0.2  15
Summit Lake (1400')  34  0  0
Alyeska Mid (1700') 35   0 0.1   6


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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812')  25 E  20 48 
Seattle Ridge(2400') 28  NE  12 32



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: Oct 11, 2014 )

Glacier District
Johnson Pass: Closed
Placer River: Closed
Skookum Drainage: Closed
Turnagain Pass: ClosedClosed as of April 23rd.
Twentymile: Closed
Seward District
Carter Lake: Closed
Lost Lake Trail: Closed
Primrose Trail: Closed
Resurrection Pass Trail: Closed
Snug Harbor: Closed
South Fork Snow River Corridor: Closed
Summit Lake: Closed

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.

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