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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Wendy Wagner  
Tuesday, December 9th 2014
Created: Dec 9th 5:50 am
3 Considerable Alpine / Above 2,500' Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision-making essential.
3 Considerable Treeline / 1,000'-2,500' Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision-making essential.
0 NO RATING Below Treeline / Below 1,000'
 Show the Complete North American Avalanche Danger Scale
Special Announcement

Our thoughts and condolences go out to the family and friends of Erik Peterson who was tragically killed Saturday, Dec 6th while skiing in the Alaska Range. Preliminarily information can be found HERE.


Upcoming FREE Avalanche Awareness talks from CNFAIC forecasters:

Tonight, Dec 9th at 6pm - REI Anchorage.  A few spots are left.  Visit the REI website to sign up.

Thursday Dec 11th at 6:30pm - Alaska Avalanche School in Anchorage.  Installment #2 of our Fireside Chat Series.  This evening's topic will be "Avalanche Basics and Rescue Fundamentals".


The Bottom Line

CONSIDERABLE avalanche danger exists this morning on all aspects above 1500ft. Below 1500ft a lack of snow cover results in no rating. Over the past 48-hours, heavy rainfall at the mid-elevations and below has created widespread natural wet avalanche activity. With a decrease in precipitation expected today, natural avalanche activity is expected to decline. However, human triggered wet avalanches, up to a foot deep, will remain likely on slopes steeper than 35 degrees. Areas of most concern are all aspects in the elevation band from 1500ft to 3000ft. At the high elevations above 3000ft, storm snow instabilities exist in the form of wind slabs, cornices and loose snow sluffs.

For today, avoiding slopes steeper than 35 degrees harboring saturated and wet snow is recommended. In the upper elevations with dry or moist snow, cautious route finding and skilled snowpack evaluation is essential.

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The next advisory will be Thursday Dec11th at 7am.

Avalanche Outlook for Wednesday: The avalanche danger is expected to decrease Wednesday due to a decrease in precipitation and a possible break in cloud cover. Temperatures should remain very warm however and extra caution will continue to be warranted for wet avalanches below 3000ft and wind slab avalanches above 3000ft.


Primary Concern

Yesterday marked the second, and most intense, period of rain on snow. Many wet loose avalanches were observed on all aspects along with two wet slab avalanches between 1500ft to 3000ft (photos below). Today precipitation is expected to decrease with potentially .3-.5" of rain falling below 2500ft.

Wet avalanches are common during extended periods of rain and warm temperatures. They typically start on steep terrain with rollerballs initiating under cornices, trees, rocks or underfoot that subsequently entrain more and more snow as they gain momentum and move downslope. If caught in a wet avalanche it is very difficult to escape as the heavy wet snow can quickly knock you off your feet, twist a knee or break a leg. Debris has the potential to run further than expected due to a melt/freeze crust 8-18" below the surface (mid-pack) providing a uniform sliding surface.

Photo below is a wet slab avalanche on the West face of Lipps Ridge (2800ft).

 

Wet loose avalanches off of Tincan's Southwest facing CFR ridge (2500ft)


Secondary Concern

Despite the grim facts concerning the wet snow stated above, at the high elevations it is snowing. Above 3,500' new snow amounts during the past 48-hours are estimated between 2 and 3+ feet in the Turnagain Pass zone - up to twice that in other areas such as Portage and the Girdwood Valley. We have little information on how this new snow is adjusting, however what we do know is this is a significant load in a short period of time that warrants respect.

Storm snow instabilities will be in form of wind slab, cornices and loose snow sluffs. With ridgetop winds and precipitation decreasing overnight, these instabilities should gain strength rather quickly. This is due to the warm temperatures of the new snow along with no known preexisting weak layers in the snowpack at these upper most elevations. 

 


Additional Concern

Although we did not see any glide avalanche activity yesterday, the poor visibility and known existence of glide cracks between 1,500 and 3,500', is enough evidence that these types of avalanches remain a concern. As with the travel advice for wet avalanches above, today is a day to avoid slopes steeper than 35 degrees and to steer clear of runout zones.


Mountain Weather

Yesterday's weather was warm, wet and windy. During the past 48-hours Turnagain Pass has received 2.5 inches of water with greater amounts in the Girdwood and Portage Valleys. The rain/snow line hovered ~2000 feet yesterday and possibly up to 2500 feet in areas. Ridgetop temperatures have been ~30F and winds were predominantly from the East, averaging 30-40mph with gusts in the 60’s. 

Overnight, temperatures have increased slightly and the rain/snow line looks to be just above 2000 feet with precipitation diminishing. Winds have also decreased and are remaining steady in the teens to 20’s mph along ridgetops from the East. Today, Tuesday, we are expecting .3-.5" of rain below 2000-2500' with 2-4" of wet snow above. Ridgetop Easterly winds should remain in the 10-20mph range with temperatures near 30F.

The low-pressure system that moved through yesterday is headed inland today bringing a slight break in precipitation. However, warm temperatures are expected to continue over the next few days with periods of light rain and freezing rain. This should continue through Thursday, followed by another low-pressure system that could bring more precipitation closer to the weekend for Southcentral Alaska.  

 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 36  1.4  19 
Summit Lake (1400') 35  0.2 
Alyeska Mid (1700') 37  1.3  12 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 29  25  61 
Seattle Ridge(2400') 31  18 47 

 

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: Nov 18, 2017 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: Closed
Placer River: Closed
Skookum Drainage: Closed
Turnagain Pass: ClosedOnly a few inches of snow sits at the motorized lot, not enough to open for snowmachining at this time. Updated Nov. 18, 2017
Twentymile: Closed
Seward District
Carter Lake: Closed
Lost Lake Trail: Closed
Primrose Trail: Closed
Resurrection Pass Trail: ClosedResurrection Pass trail is expected to open to snowmachine use during the 2017/18 winter season.
Snug Harbor: Closed
South Fork Snow River Corridor: Closed
Summit Lake: Closed

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
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