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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Jon Gellings  
Wednesday, February 23rd 2011
Created: Feb 23rd 6:43 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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Arctic Air Walkers
The Bottom Line
Good morning backcountry travelers. This is Jon Gellings with the Chugach National Forest Avalanche Information Center on Wednesday, February 23rd at 7am. This will serve as 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).

ANNOUNCEMENTS
We have a new survey for you to fill out, which would hopefully involve all backcountry skiers in North America. The focus is on the differences between all male, all female, and mixed gender ski groups, and is actually being conducted by a local APU student. Please fill it out, which should take about 10 minutes.
Click here to take survey

BOTTOM LINE
Today, the avalanche danger is MODERATE, with pockets of CONSIDERABLE. The strong winds from the past few days look as though they have finally settled down, and they have definitely affected our snowpack. The decreasing danger is aimed directly at this hazard, since loading processes have seemingly ceased in most areas, but human triggered avalanches are still likely. Slopes that have not received a wind load still contain a steady MODERATE danger for deep slabs, which are still possible to trigger on slopes steeper than 30 degrees in areas with a relatively shallow snowpack (less than 2 meters deep).

AVALANCHE DISCUSSION
The snowpack surface in Turnagain Pass is very heavily wind affected in most places not protected by trees. Hard wind slabs, soft wind slabs, sastrugi, and wind crusts are the replacements for the cold smoke powder many people have been reporting over the past weeks. These surface features also make observing recent avalanches fairly difficult in some areas. We were able to see many things that looked like new avalanches in wind loaded areas yesterday, but the winds nearly obliterated their tracks, leaving a little feeling of doubt on how new they really were.



539-P2220022 (outlined).JPG


These avalanches in the same gulley on Seattle Ridge do not easily show their tracks, but the upper one was very crisp, meaning that it was quite recent and perhaps failed overnight. There is a pocket of deeper instabilities about halfway down the slope that pulled out down to the ground, which is the first slab breaking into these older weak layers in Turnagain Pass in several weeks. This goes to reiterate the fact that this instability can be triggered in Turnagain Pass, not just in CNFAIC Staff areas.

One person wrote in an observation for Hatcher Pass giving details of a slab avalanche that happened on Monday. Although this is outside of our advisory area, I feel it is worth mentioning. Two people were climbing a North-facing chute on Marmot when it broke 2-2.5ft deep, carrying them ~100 yards and partially burying one of them. There are no details of injuries, but it goes to show that instabilities are potentially everywhere this year. Collapses and shooting cracks were also observed in the Summit Lake area as recently as yesterday, so there is anCNFAIC Staff heads up.

Signs that you are travelling on a wind slab include seeing shooting cracks, and hearing hollow sounds on hard snow. A soft slab could be easily triggered near convex rollovers and/or ridgelines, while hard slabs are a bit more unpredictable. They tend to fracture when a person gets out in the middle of them, and break like glass sending travelers to the bottom of the slope. And the possibility still exists for a moving avalanche to break into deeper weak layers, creating a larger avalanche.

We are still concerned with the possibility of deep slab avalanches, and the slab near Twin Peaks is the largest one recently observed. It propagated fairly wide, and slid down to the ground in most areas. These deep slabs can possibly be triggered in regions with a snowpack generally less than two meters deep, and conditions are not likely to improve until we get a large storm with lots of water which causes these layers to fail and eventually strengthen. Until then, know the snow you are on to avoid this hazard.

Here are two side notes of information:
1. We have not seen a perceived LOW danger since between Christmas and New Years. We would all love to see stable conditions, but we simply cannot rule out the possibilities and/or likelihoods of triggering a life-altering slab avalanche.
2. The Western Chugach National Forest (our area) has several NRCS sites which measure snow-water equivalent, and all are recording 66-88% of normal for this time of year. This low-snow year is more comparable to an intermountain or continental snowpack, versus our normal maritime snowpack.

Encyclopedia of avalanche terms.

WEATHER ROUNDUP
Wind sensors on weather stations are showing decreased winds, so hopefully they are done blowing for the time being. Temperatures should be similar to yesterday, with solar warming potentially starting up on Southern aspects. New precipitation is unlikely today, as radar, satellite, models and forecasts all show clear to partly cloudy weather.

Kevin will issue the next advisory tomorrow morning at 7am. If you get out in the backcountry give us a call at 754-2369 or send us your observations using the button at the top of this page. Thanks and have a great day.

NWS Turnagain Pass Weather Forecast

WEATHER STATION SUMMARY for Turnagain Pass:
-3800 Sunburst Wx Station-
Temperature 15 F. West winds 5 mph gusting to 9 mph.
-2600 Seattle Ridge Wx Station-
Temperature 15 F. Southwest wind 1 mph gusting to 6 mph.
-1800 Center Ridge Wx Station-
Temperature 9 F. 0" new snow. 86 total snow depth.

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 11, 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: OpenWide swaths of open river in the Placer Valley. Travel with extreme caution!
Skookum Drainage: ClosedSKOOKUM DRAINAGE CLOSED TO MOTORIZED USE ON APRIL 1 annually as per the Chugach National Forest Plan document.
Turnagain Pass: Open
Twentymile: ClosedClosed for the remainder of the 2017 season.
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

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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.


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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