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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Wendy Wagner  
Saturday, January 18th 2014
Created: Jan 18th 6:41 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.
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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The Hoarding Marmot
The Bottom Line

A CONSIDERABLE avalanche danger exists today both above and below treeline on all aspects. The brunt of yesterday's warm, wet and windy storm has moved through but the snowpack is still adjusting to the shock. Though natural avalanche activity has slowed down with the end of precipitation and cooling temperatures overnight, human triggered avalanches are still likely. These avalanches have the potential to be large, break near the ground and take out entire slopes.

Very conservative travel is recommended again today. Simply put, this means avoiding all avalanche terrain (slopes 35 degrees or greater) including runout zones with steep slopes above you. 

For anyone thinking of heading up North, check out the Hatcher Pass Saturday am Advisory.


Primary Concern

Avalanche activity from yesterday:

Yesterday’s heavy rain below 2,000' and wet snow above 2,000' combined with very warm temperatures induced a widespread natural avalanche cycle. This extened to the Summit Lake area as well. We were able to get video footage of one natural slide in Portage Valley - video below. Additionally, the AK DOT Avalanche Program was able to trigger several large avalanches along the Seward Highway – one these can be seen in a video HERE.

The start zones for much of yesterday’s activity was in the dry snow above 3,000’. These slides turned wet as they descended due to entrainment of wet snow below treeline. You can see in the video below from Portage Valley how the powder cloud dissipates as the debris encounters the wet snow.

 

 

The slightly cooler temperatures along with breaks in cloud cover overnight will help limit any natural acitivity today. Much of the pack below treeline was draining water rapidly yesterday and today there may be a slight refreeze on the surface. The main areas of concern for wet avalanches will be near and just below treeline or in a gully at sea level elevations where debris can be funneled.


Secondary Concern

The shock of up to 3” of water weight in 24-hours yesterday did a number to the pack – as can be seen in the above videos and in our field day HERE. At the upper elevations this has added around 2' of new snow along with rain on snow below treeline. The weak snow near the base of pack that is the culprit for many of our large avalanches is once again being overloaded. Though visibility was limited yesterday, it is likely that many of the debris piles seen occurred by an avalanche breaking near the ground and propagating across slopes at the mid to upper elevations. 

For today, the weather has abated but don't count on the weak snow near the ground to have adjusted to the new load yet. There is much uncertainty going into today but the fact remains that during the past 24-hours we have had a significant avalanche cycle and there are slopes likely teetering on the edge just needing a human trigger.


Additional Concern

At the upper elevations - above 3,000' - temperatures were cold enough for around 2' of snowfall during yesterday's storm. Storm snow instabilities, mainly in the form of wind slabs are likely to be found and potentially triggered. With the warm temperatures these are likely to settle out within the 24-hour window - however, this is relegated to the storm snow and not the persistent slab issue mentioned above.

There is also the potentail for any storm snow avalanche to step down and trigger a larger slide breaking in the weak snow at the base of the pack.


Mountain Weather

A fast moving and powerful storm moved through yesterday with rain below 2,000’ and heavy snow above. Ridgetop winds associated were from the East and averaged in the 50-60mph range with a max gust in the past 24-hours of 106. Temperatures at treeline were mainly in the upper 30’s and decreased to the low 30’s by the end of the precip.

Storm totals beginning Thursday night ending 6am this morning:
Turnagain Pass (1880’) -   2.2” water, mostly rain (4” wet snow)
Alyeska Mid (1700’) -  Roughly 3-3.5” water, mostly rain (5” wet snow)
Summit Lake (1400’) -  1.3” rain

Overnight the skies have broken slightly as the main portion of the system is now to our North. There is a section of clouds and precipitation that is being wrapped around the low center which may add another 1-3” of snow today. This has colder air entrained so snow levels should drop to around 400’. Ridetop wind today will be from the Southeast and in the 20mph range. Temperature at treeline will be around 30F and sea level mid 30’sF.

Sunday, another low pressure system heads our way that looks to be somewhat similar to yesterday’s storm. Stay tuned.

 

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
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