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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Graham Predeger  
Tuesday, December 15th 2015
Created: Dec 15th 6:33 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.
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Special Announcement

Fireside Chat #3 – Human factors and decision-making on Thursday, Dec 17th!! Join our newest CNFAIC forecaster, Aleph Johnston-Bloom Thursday night from 6:30-8:00pm in Girdwood at the Glacier Ranger Station (Forest Service office) for an introduction to what avalanche professionals and psychologists refer to as the “human factor” as it relates to decision-making in the backcountry.

More areas are open for over snow vehicles on the Seward Ranger District today!  Please see updated table at the bottom of this page.


The Bottom Line

With 6-12+ inches of snow falling on Sunday night/ Monday morning from sea level to ridgetops there is a MODERATE avalanche danger in all elevation bands today.  Storm snow instabilities and loose snow avalanches are the primary concern today and are most likely to be encountered in very steep terrain.

Ice climbers: Snowfall totals in Portage Valley have been verified at 12” or more yesterday.  This is potentially more than a “moderate” avalanche problem for this user group given the extreme and complex nature of the terrain.  


Primary Concern

Observations from yesterday are pointing toward an overall snowpack that continues to adjust to this latest pulse of snow.  The weak snow above the Thanksgiving rain crust continues to show signs that it is gaining strength and didn’t prove to be a concern in our snowpits yesterday.  Keep in mind this set up though (see secondary concern below) and recognize that areas where wind loading has occurred, there will be more weight on this weak snow/ storm snow interface.  Large triggers such as a snowmachine could prove enough to tickle out a fresh storm slab or wind slab 2-3’ deep.

Skiers pushing into steeper, upper elevation terrain (above 3500’) may also find fresh wind slabs in the 2-3’ range as we had a short but strong wind event on Sunday night.  In areas protected from the wind and lower elevations, the surface is quite unconsolidated.  Generally with more snow on the northern end of Turnagain pass, loose snow sluffs will prove to be fast moving and high volume today, particularly in steep terrain (greater than 40 degrees).

CNFAIC forecasters are elated to be able to utilize snowmachines again as a forecasting tool after last winters "snow drought" at trailhead locations.  Here, Graham Predeger digs in to look at our current snowpack structure at 2400' above 2nd Bowl (Jr's bowl) on the backside of Seattle ridge. 


Secondary Concern

We will continue to track the Thanksgiving rain crust/ facet combo (and buried surface hoar layer) until it is buried more than 3 feet deep AND proves dormant.  Though not reactive recently, all the ingredients are present to bake that cake (2’+ storm slab/ weak snow/ stout bed surface).  For the moment, look at this avalanche problem as an additional reminder to maintain safe travel protocols, and ensure you and everyone in your crew is carrying proper rescue equipment and knows how to use it.


Mountain Weather

Low-level fog persisted most of yesterday near sea level with broken clouds and partly sunny skies above about 500’.  The snowfall shut off early yesterday morning with no new precipitation added during the daylight hours.  Winds were calm (single digits) throughout the day and temps were in the 20’s from valley bottom to ridgetops. 

Today, temperatures are starting out slightly inverted, promoting valley fog, though with a weak pulse of moisture arriving mid to late morning, that should usher in easterly winds in the 25-40mph range at ridgetops and act to mix the air a bit.  We may see 1-3” of snow falling from sea level and up, around the eastern Turnagain arm region with temperatures in the 20’s F at ridgetops and low to mid 30’s F at sea level.

More active weather is on tap through the workweek as another low pressure moves into the Gulf and begins to affect Kodiak as early as tomorrow.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 24  39 
Summit Lake (1400') 23   14
Alyeska Mid (1700')  25  0  33

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 19   4 28 
Seattle Ridge(2400') 20   N/A  N/A  N/A

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
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