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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   John Fitzgerald  
Monday, January 5th 2015
Created: Jan 5th 6:12 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.
1 Low Treeline / 1,000'-2,500' Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
0 NO RATING Below Treeline / Below 1,000'
 Show the Complete North American Avalanche Danger Scale
Special Announcement

Conditions at Hatcher Pass led to a few close calls over the weekend.  Weak snow at or near the ground have produced large human triggered avalanches.  Click HERE for video and photos of these avalanches.  These are great examples of persistent weak layers producing large avalanches several days after loading events.  If you are heading up to Hatcher check http://hatcherpassavalanchecenter.org/ for up to date snow and avalanche information.

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Join us for our final Fireside Chat this Thursday, January 8th, in Anchorage! Topic: Mountain Weather and Snowpack. We will be taking a close look at the current state of the snowpack at Turnagain Pass along with a look into "when is it going to snow?".


The Bottom Line

The avalanche danger is MODERATE in the Alpine (above 2,500), where dense slabs 1-3’ in depth could be triggered in steep terrain today.  This is a low likelihood/high consequence scenario, in that avalanches, if triggered, have the potential to injure or bury a person.

The danger is LOW at Treeline (1,000-2,500'), where avalanches are unlikely.

Below Treeline (sea level to 1,000') there is no rating due to insufficient snow coverage.


Primary Concern

Layers of weak snow continue to linger below the surface.  On Turnagain Pass the predominant layer of concern is buried surface hoar roughly 2 feet down.  This setup exists mainly above 2,500’.  In the Girdwood Valley and Summit lake areas that layer is facets and is less even in its distribution.  While it has been over 2 weeks since we have seen significant precipitation and about a week since significant winds have loaded slopes, the potential still remains for avalanches to occur on these buried weak layers.

The likelihood of triggering an avalanche anywhere from 1-3 deep is on the low end of the scale.  However, if one were to trigger an avalanche there is still the potential for avalanches to propagate across slopes and be large enough to carry, injure or bury a person.

Most surfaces are firm and supportable around the forecast area.  Slabs are generally strong and can support a lot of weight.  Trigger points in the form of shallow snow and steep rollovers are the most likely areas to initiate an avalanche today.  Slabs of this hardness can break above you making escape very difficult.

If venturing onto steep terrain practice good travel habits:
Expose only one person at a time
Utilize islands of safety for spotting and re-grouping
Identify escape routes in the event of a slab releasing
Communicate route decisions and plans within your group effectively
Be aware of groups above and below you and avoid exposing other groups to avalanche hazard


Additional Concern

An “outlier” concern today are old wind slabs.  High winds of a week ago created very dense slabs on the surface as thick as 1 foot.  These slabs have shown to be generally non-reactive.  However, it is still worth keeping these slabs in mind especially if getting onto steep (>40 degree) unsupported slopes.


Mountain Weather

Clear, cold and calm was the name of the game yesterday.  Temperatures were more seasonable with ridgetop stations reporting in the teens F.  Winds have been light generally out of the Northwest and no new precipitation has fallen.

Today expect similar conditions, as a large ridge of High pressure continues its dominance over mainland Alaska.  Temperatures at ridgetops will be in the 20 degree F range.  Some valley locations will experience a strong inversion this morning and keep temps in the single digits F where valley fog has developed.  Winds will be light out of the East at 5-10mph.

Clouds should move over the area Tues night as a large band of moisture attempts to push up towards Southcentral AK from the South.  The next chance for precipitation will come mid to late week as the blocking ridge looks to potentially break down.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 13 0 0 33
Summit Lake (1400') 2 0 0 6
Alyeska Mid (1700') 13 0 0 25

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 16 WNW 3 15
Seattle Ridge(2400') 14 VAR 6 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: Mar 28, 2017 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: OpenPlease park on road in and leave the turnaround (near outhouse) open for trailers to turn around.
Placer River: OpenPlacer remains open but SKOOKUM DRAINAGE will close to motorized use on April 1st.
Skookum Drainage: OpenSKOOKUM DRAINAGE CLOSES TO MOTORIZED USE ON APRIL 1 annually as per the Chugach National Forest Plan document.
Turnagain Pass: Open
Twentymile: Open
Seward District
Carter Lake: Open
Lost Lake Trail: OpenPlease STAY ON existing and hardened trail surface through the lower sections of this route.
Primrose Trail: OpenPlease STAY ON existing and hardened trail surface through the lower sections of this route.
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: Open
South Fork Snow River Corridor: Open
Summit Lake: Open

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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