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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Heather Thamm  
Tuesday, January 31st 2017
Created: Jan 31st 5:34 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.
 Show the Complete North American Avalanche Danger Scale
Special Announcement

Dangerous avalanche conditions persist in many areas around Southcentral Alaska
including the Southern Kenai Mountains, Hatcher Pass and Anchorage Front Range

  • A preliminary report is out with a few photos regarding the snowmachine avalanche fatality in the Snug Harbor area on Saturday. The final report with finalized details on the events, rescue and snowpack analysis will be posted in the next couple days. Our thoughts continue to be with the victim's family, friends and rescuers.
  • The Southern Kenai Mountains, including Snug Harbor and Lost Lake zones continue to have dangerous avalanche conditions. This region is out of the advisory area but large human triggered slab avalanches 3-5 thick are possible on slopes over 35 degrees. Careful snowpack evaluation, cautious route-finding and conservative decision-making are essential.
  • Click HERE for the Hatcher Pass Avalanche Center advisory and HERE for recent snowpack observations.

The Bottom Line

The avalanche danger is MODERATE at all elevations in Turnagain Pass but could rise to CONSIDERABLE in the alpine by the afternoon. Human triggered wind slabs 6”-15” thick are possible on slopes steeper than 35 degrees and slab size will depend on how much snowfall we receive today. There is also the possibility for triggering a large (2-3') slab avalanche that breaks lower in the snowpack. The most suspect areas are on the South end of Turnagain Pass where the snowpack is shallower and there has been little traffic this season. Last, cornice falls are still a concern along ridgelines and small wet loose avalanche are possible below 1000’ should snow turn to rain.

Girdwood Valley:  A shallower snowpack exists in the Girdwood Valley and slab avalanches have the potential to be larger, over 3' thick, and break near the ground. Expect wind loading and snowfall today to add stress to an already stressed out snowpack.

Summit Lake:  Dangerous human triggered slab avalanche conditions persist in the Summit Lake zone. Check out the Saturday Summit Summary HERE

**The probability of triggering one of these large slabs is decreasing but the consequences remain high. This is more reason to be sure to carry your rescue gear and practice safe travel protocol - such as exposing one person at a time, grouping up in safe zones, having escape routes planned and watching your partners!  


Primary Concern

Wind Slabs: Yesterday afternoon ridgetop winds bumped up into the 30’s mph from the East and wind loading was observed in the alpine. Today an additional 3-8” of snow is expected and ridgetop winds will be in the 15-30mph range. Expect wind slabs to be tender, 6”-15” thick on leeward terrain features.  These fresh slabs are expected to be sensitive to human triggers on slopes steeper than 35 degrees. Visibility may be limited today, but watch for blowing snow, stiffer snow over softer snow, or cracks that shoot out from your snowmachine or skis. Slope testing small (low consequence) slopes and performing quick hand pits are all good ways to assess whether you have found a wind slab. Should snowfall become heavy today or more snow falls than forecasted, these slabs could increase in size and become more consequential. Be prepared to change your plans should conditions worsen. 

Wet Snow: There is some uncertainty today in how warm temperatures will rise and how much precipitation will fall. Should snowfall transition to rain, small wet loose avalanches are possible in the lower elevations below 1000’. These are not likely to bury a person, but could catch you by surprise especially in areas with terrain traps. This will be an important thing to keep in mind if headed to the Placer Valley today.

Cornices have been growing in size over the last few weeks and with additional loading today could be extra tender. Give these unpredictable features extra space along ridges and avoid being under these features, as they could release naturally and without warning.

Cross loaded gullies with pillowed snow along ridges - an example of terrain features that may harbor tender wind slabs today. Photo taken 1/30/17 of an East facing slope on the South end of Seattle Ridge near Bertha Creek Camp Ground. 

 


Secondary Concern

The January 26th storm event added 2-3' of snow to the upper elevations and overloaded a variety of weak layers causing a widespread avalanche cycle in the region. The good news is the snowpack in the heart of Turnagain Pass is showing signs of adjusting to the load, the bad news is other areas are not. This can make for difficult snowpack assessment as the weak layers of concern (depth hoar, facets and buried surface hoar) are lurking anywhere from 2-4+ feet below the surface. Thicker snowpacks, as found at Turnagain Pass, had a stronger snowpack to begin with and has allowed for a quicker adjustment. This is opposed to the persisting unstable snowpack found South of Turnagain Pass and the Girdwood Valley.

In Turnagain Pass - this is a high consequence but low probability situation and may require a big trigger like multiple people on a slope or finding just right trigger spot in a thinner area of the snowpack. In Girdwood, Johnson Pass, and Summit Lake today’s storm will be adding stress to an already stressed snowpack and tipping the balance may be easier in these locations. Should you experience collapsing “whumpfing” sounds, or see any avalanche activity, these are obvious clues the snowpack is unstable. 

If choosing to ride or ski the steeper terrain, we recommend using safe travel protocol, only exposing one person at a time and grouping up in safe zones. If a large slab is triggered it may run further than expected and wrap around terrain features taking out mid-slope relative safe zones.

A Northern aspect of Pete's South where a generally thinner snowpack exists and where there's more potential to trigger an avalanche in an older deeper layer of the snowpack. Photo taken yesterday 1/30/17.


Mountain Weather

Yesterday temperatures were on the rise throughout the day approaching the low 30F’s near sea level by late afternoon. Skies were cloudy becoming overcast by mid day. Moderate Easterly ridge top winds, 15-30mph, bumped up into the mid 20’s mph by late afternoon with gusts in the 40’s. Only an inch of new snow was recorded overnight. 

Today a frontal system has pushed into the Gulf of Alaska and warm temperatures and snowfall are expected. There is some uncertainty as to how much will precipitation will fall, with a range from 3-8”, but more or less is possible. Easterly ridge top winds are expected to be moderate,15-30mph. Above freezing temperatures are expected below 1000’, and rain may fall into this elevation band today. Tonight there is a chance for an addition 2-6” of snow.

Tomorrow temperatures are expected to cool and snow showers are possible. Winds are expected to decrease this evening and clear skies are in the forecast later in the week.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 29  .1  58 
Summit Lake (1400') 25  .1  25 
Alyeska Mid (1700')  27 trace  .06  51 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 19  ENE  19  49 
Seattle Ridge(2400') 20  SE  21  49 

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
© 2017 Chugach National Forest Avalanche Information Center. All rights reserved.
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