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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Wendy Wagner  
Thursday, March 30th 2017
Created: Mar 30th 6:26 am
4 High Alpine / Above 2,500' Travel Advice: Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
3 Considerable Treeline / 1,000'-2,500' Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision-making essential.
3 Considerable Below Treeline / Below 1,000' Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision-making essential.
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Alaska Mountaineering and Hiking
Special Announcement

Tomorrow is the deadline for applying for your 2017 PFD!! Please consider showing your support for public avalanche centers when applying - the Friends of the Chugach National Forest Avalanche Center is an official Pick. Click. Give. organization!

*A reminder that the Skookum Valley closes to motorized use on April 1st, this Saturday.  All other motorized areas remain open - see area status on the bottom of this page for more information.


The Bottom Line

There remains a HIGH avalanche danger in the Alpine (above 2,500'). Natural wind slab avalanches 2-4' thick will be likely due to strong winds forecast today in the mountains surrounding the Eastern Turnagain Arm (such as Turnagain Pass, Girdwood Valley and Placer Valley). Below 2,500' and in areas out of the wind, a CONSIDERABLE avalanche danger exists for storm slabs 1-2' thick composed of new snow from Tuesday night's storm. Natural cornice falls are also possible and could trigger slabs below along with loose snow avalanches. With the continued active weather pattern, today will be another day to avoid avalanche terrain.

*A potent storm system moving in tonight is expected to keep the danger elevated into the weekend. 

Hiking in Portage Valley:  Travel along, and past, the designated Byron Glacier trail is not recommended due to exposure to avalanche terrain. Natural avalanches are possible today that could send debris to valley floors.

Summit Lake:  Roughly 6-8" of new snow fell as of yesterday. Strong winds are expected in this region as well. Read the Saturday Summit Summary HERE.

 


Primary Concern

After a brief break between storms, another system is literally on the doorstep. This one is characteristic of a Classic Chugach Storm - warm, wet and windy. Opposed to Tuesday night's storm which was cool and calm; meaning 1-2+ feet of new snow fell with relatively light winds. Avalanche activity yesterday consisted of many natural and remotely triggered storm slab avalanches in the Girdwood Valley and Placer Valley where over 2 feet of snow fell. Observers noted significant propagation with these slabs which points to the fact the new snow is sitting on weak old snow. In general, visibility was very hampered and at Turnagain Pass where only a foot of new snow fell, only one natural avalanche was seen on Tincan's Southerly face under Hippie Bowl

As of 5am this morning winds from the East are just ramping up - expected to average in the 25-40mph range. Snow is expected to begin later today with 2-6" forecast by 6pm and another 6-12" forecast tonight. The strong winds will be the main contributing factor to avalanche activity today, yet there are other avalanches issues present. The whole run down is:

WIND SLABS and CORNICES:
Strong winds today should have an easy time moving yesterday's new snow around and loading leeward slopes, creating large wind slabs and cornices. These are likely to release naturally and could entrain enough snow to run quite far. In areas such as Portage Valley where over 2' of new snow has already fallen, these slabs could run to sea level.

STORM SLAB AVALANCHES:
In areas out of the wind, expect the recent storm snow to still be touchy. Where up to 2 feet of new snow has already fallen, such as Girdwood Valley and Placer Valley, human triggered slab avalanches 1-2' thick are still likely, as was the case yesterday. At Turnagain Pass, with only a foot of new, shallow slabs and sluffs are possible.

LOOSE SNOW AVALANCHES:
Sluffs in the new snow should be expected on all aspects and elevations - this issue is overshadowed however by the much more concerning avalanche problems mentioned above.

All this said, with the active weather over the region, travel is avalanche terrain is not recommended. Sticking to the flats, well away from runout zones, heading to the local ski hill or filing your PFD/doing taxes are all good options for the next few days!

Five Sisters slide path in the Portage Valley. Skies opened just enough to see several crowns 2-3' thick in the recent storm snow; hard to see in the photo. Fresh debris did not run to the valley floor, only part way down over the older debris.

 

 

 

14" of new snow sits over facets on North aspects (photo below) and a sun crust (.5 - 1" thick) on Southerly asepcts at Turnagain Pass on Tincan.

 

Satellite image from 6:00 am (infrared image) of the large low-pressure headed our way today and forecast to churn warm, wet and windy weather in the region through the weekend.

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Secondary Concern

Don't forget that our snowpack harbors several old layers of weak snow. Avalanches releasing in the storm snow have the potential to 'step down' into these layers. Furthermore, as the new snow piles up and begins to stick to the old snow surface, avalanches breaking into them is possible as well. Both of these situations can create a much larger avalanche - something to look for in the coming days.


Mountain Weather

Intense snowfall from Tuesday night's storm tapered off significantly by noon yesterday. Storm total was 12-14" of new moist snow on Turnagain Pass and 24-34" in the Girdwood Valley and Placer Valley. Skies were mostly cloudy and temperatures were warm - upper 30'sF at sea level and the mid 20'sF along the ridgelines. Ridgetop winds during the past 24-hours have been light (5-10mph) from the East - but have just bumped to moderate (15mph) as of 5am this morning.

Today, ridgetop winds will continue to increase with averages up into the 25-40mph range from an Easterly direction with gusts into the 50's+ mph. This is in advance of a large low-pressure system moving in bringing warm, wet and windy weather. Precipitation should begin later this morning with 2-6" of snow to sea level accumulating by 6pm and another 6-12" by 6am tomorrow. Temperatures should climb today into the low 30's F at sea level and stay in the mid 20'sF along the ridgelines.

Tomorrow, Friday, warm air is expected to push in bringing the rain/snow line to between 500 and 1,000'. Another foot(ish) of snow is expected on Friday above 1,000'. Stay tuned as this Chugach Storm develops!

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 32  0.1  69 
Summit Lake (1400') 25  0.1  34
Alyeska Mid (1700') 27  0.35  75 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 20  NE  27 
Seattle Ridge(2400') 24  40 

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: May 16, 2017 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: Closed
Placer River: Closed
Skookum Drainage: Closed
Turnagain Pass: ClosedThanks all for a safe and fun season on the Chugach NF! Stay tuned for the 2017/18 season. #playsafe #snowtosealevel
Twentymile: Closed
Seward District
Carter Lake: Closed
Lost Lake Trail: Closed
Primrose Trail: Closed
Resurrection Pass Trail: ClosedResurrection Pass trail will be 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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