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Archives
ARCHIVED - Forecasts expire after 24 hours.
Issued
Sun, March 5th, 2017 - 7:00AM
Expires
Mon, March 6th, 2017 - 7:00AM
Forecaster
Heather Thamm
Avalanche risk The Bottom Line

A MODERATE  avalanche danger remains in the Alpine of Johnson Pass/Lynx Creek and parts of the Girdwood Valley, where wind loaded slopes have the potential to step down and trigger a deeper avalanche. It is these periphery areas that are keeping the danger elevated in our forecast zone.  

In Turnagain Pass, there is a generally LOW avalanche danger where triggering a small isolated wind slab is becoming stubborn and difficult to trigger. This avalanche problem is not likely to bury a person. Remember LOW danger does not mean NO danger, steep terrain could have high consiquences should a small wind slab or cornice fail above a terrain trap. Using safe travel protocol and evaluating the terrain for consequences will be important.  

*In Summit Lake, a widespread natural avalanche cycle occurred this week and heighten avalanche danger remains in this zone. Please see  the Saturday Summit Summary  HERE

Special Announcements

Strong winds over the past several days have affected the snow/avalanche conditions in many areas of Southcentral Alaska and the Kenai. See this report sent in to us from  the Lost Lake zone  on the Southern Kenai. Additionally, a natural avalanche was viewed in motion in the South Fork of Eagle River on Friday. For avalanche conditions at Hatcher Pass, see the HPAC Saturday morning advisory!

Avalanche Rescue Talk:  Stop by Ski AK in Anchorage for a discussion on backcountry rescue Tuesday evening! The focus will be on organized rescue, presented by Bill Romberg (AMRG) a rescue specialist with 150 Search and Rescue missions here in Alaska. The evening will begin with a short ‘state of the snowpack’ report by the CNFAIC. See you Tuesday night – more details  HERE!!

Sun, March 5th, 2017
Alpine
Above 2,500'
2 - Moderate
Avalanche risk
Treeline
1,000'-2,500'
1 - Low
Avalanche risk
Below Treeline
Below 1,000'
1 - Low
Avalanche risk
0 - No Rating
1 - Low
2 - Moderate
3 - Considerable
4 - High
5 - Extreme
Avalanche risk Avalanche risk Avalanche risk Avalanche risk Avalanche risk
Travel Advice Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features. Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern. Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding, and conservative decision-making essential. Very dangerous avalanche conditions. Travel in avalanche terrain not recommended. Extraordinarily dangerous avalanche conditions. Avoid all avalanche terrain.
Likelihood of Avalanches Natural and human-triggered avalanches unlikely. Natural avalanches unlikely; human-triggered avalanches possible. Natural avalanches possible; human-triggered avalanches likely. Natural avalanches likely; human-triggered avalanches very likely. Natural and human-triggered avalanches certain.
Avalanche Size and Distribution Small avalanches in isolated areas or extreme terrain. Small avalanches in specific areas; or large avalanches in isolated areas. Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas. Large avalanches in many areas; or very large avalanches in specific areas. Very large avalanches in many areas.
Avalanche Problem 1
  • Wind Slabs
    Wind Slabs
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.
More info at Avalanche.org

Ridgetop winds should again be moderate to strong – in the 15-25mph range from the Northwest. This is the same forecast we have seen over the last 3 days and Turnagain pass has either remained protected or the snow has blown away.  There are areas that have been partially spared by the brunt of the Northwest winds this week along the East(non-motorized) side of the road of Turnagain Pass. Folks have been able to find soft snow and venture further into the mountains without incident. That said, there are areas that have not escaped the major winds. A report yesterday confirmed Seattle Ridge to be scoured and hard pack, and most of the loose snow has blown away. Triggering a small hard wind slab is not out of the question in steep terrain in either area. Although these wind slabs will be tough to trigger, high consequence terrain (steep rocky area and and under a loaded convexity) will be the places that a wind slab could take you for a ride. Intenitfy these features and be aware of the consequences of the terrain you are riding in. 

***Although its unlikely today should you see blowing snow along ridge tops or experience a shooting crack these will be signs that wind slabs could be tender.

Smooth or pillowed surfaces, especally under a convexity or in steep rocky terrain are places to find a wind slab.

A good example of a corniced ridge that if triggered could take you for an undireable ride. Give corniced ridges lots of space! Goldpan – South face.

Additional Concern
  • Persistent Slabs
    Persistent Slabs
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.
More info at Avalanche.org

In Turnagain Pass where the snowpack has become old and tired, good stability has been found within the deeper layers of the snowpack including as far South as Lipps. Slope testers have been stepping into steeper terrain this week without incident both in Turnagain Pass and in many areas of the Girdwood Valley. There have been no reports of avalanche activity within the older layers of the snowpack in Turnagain Pass for several weeks.   

However, the wind event that started last Monday night (2/27) did cause a natural avalanche cycle in Lynx Creek/Johnson Pass zone with slabs ranging in size from 1-2’ deep with wide propagation, likely failing on the February 9th buried surface hoar. The other area in question is the Crow Pass zone, where little is known about how this shallow snowpack has faired after a week of strong winds. Until proven innocent these periphery zones remain suspect for triggering a deeper more dangerous avalanche. The layers of concern in these areas are the buried surface hoar 1-3′ deep and facets in the mid and base of the snowpack

Weather
Sun, March 5th, 2017

Yesterday was another day of clear sunny skies and cold temperatures at all elevations. Daytime warming allowed the mid and lower elevations to warm into the low 20Fs. Ridgetop winds during the past 24-hours have averaged near 10mph with gusts into the 30’s from the Northwest.  

As Southcentral Alaska sits in a holding pattern of sorts, we can expect similar sunny skies today with continued Northwest winds. Temperatures should warm again today and may reach the low 20F’s below 3,000′. Ridgetop winds are expected to remain from the North and West in the 15-25mph range with stronger gusts.  

Clear skies and cold temperatures are expected over the next week as a blocking pattern of high pressure over Alaska dominates mainland, Alaska. Keep tabs on what the NWS is finding at the bottom of their Forecast Discussion – Long Term Forecast!

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 10   0   0   62  
Summit Lake (1400′) 10   0   0   29  
Alyeska Mid (1700′) 13   0   0   58  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 5   W   7   23  
Seattle Ridge (2400′) 10   NW   12   35  
Observations
Recent Observations for Turnagain Pass
Date Region Location
02/25/24 Turnagain Observation: Kickstep NE Bowl
02/24/24 Turnagain Observation: TinCan Backdoor/ Center Ridge
02/22/24 Turnagain Avalanche: Lynx Creek
02/22/24 Turnagain Observation: Turnagain, Seattle, Mt Ascension
02/21/24 Turnagain Observation: Tincan Trees
02/21/24 Turnagain Observation: Sunburst
02/20/24 Turnagain Avalanche: Tincan
02/20/24 Turnagain Observation: Seward Highway across from Johnson Pass TH
02/19/24 Turnagain Avalanche: Base of Seattle Ridge
02/18/24 Turnagain Observation: Lynx creek
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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.