Turnagain Pass Avalanche Forecast RSS

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Mon, March 5th, 2018 - 7:00AM
Expires
Tue, March 6th, 2018 - 7:00AM
Forecaster
Wendy Wagner
The Bottom Line

The avalanche danger remains  MODERATE  above 1000′ on all aspects. Old wind slabs, up to a foot thick and sitting on weak snow, will be possible to trigger along ridgelines and in cross-loaded gullies. A larger slab avalanche (up to 2′ or more thick) that breaks in weak layers deeper in the snowpack also remains possible above 1,000′.  

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Mon, March 5th, 2018
Alpine
Above 2,500'
Moderate (2)
Avalanche risk
Treeline
1,000'-2,500'
Moderate (2)
Avalanche risk
Below Treeline
Below 1,000'
Low (1)
Avalanche risk
Alpine
Above 2,500'
Avalanche risk
Moderate (2)
Treeline
1,000'-2,500'
Avalanche risk
Moderate (2)
Below Treeline
Below 1,000'
Avalanche risk
Low (1)
Danger Scale:
No Rating (0)
Low (1)
Moderate (2)
Considerable (3)
High (4)
Extreme (5)
Avalanche Problem 1
  • Persistent Slabs
    Persistent Slabs
  • Almost Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic
    Very Large
    Large
    Small
    Size
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.

Likelihood of Avalanches
This graphic depicts how likely you are to trigger avalanches or encounter natural avalanches while traveling on avalanche prone slopes. Unlikely means that few avalanches could be triggered in avalanche terrain and natural avalanches are not expected. The chance of triggering or observing avalanches increases as we move up the scale. Certain means that humans will be able to trigger avalanches on many slopes, and natural avalanches should be expected.

Size of Avalanches
This graphic depicts the potential size and destructive force of expected avalanches. Small avalanches are not large enough to bury humans and are relatively harmless unless they carry people over cliffs or through trees or rocks. Moving up the scale, avalanches become large enough to bury, injure, or kill people, large enough to bury or destroy vehicles and break a few trees, and large enough to destroy railway cars, buildings, or a substantial amount of forest. Historic avalanches are massive events capable of destroying villages and gouging or altering the landscape.
More info at Avalanche.org

After a month with very little precipitation, weather models are showing potential for a snowy week ahead of us. This is good news for powder hungry folks, but we can’t forget about our current state of the snowpack. As we have been discussing for some time, there are several weak layers in the pack that continue to show signs of reactivity. Hard wind slabs formed by last week’s wind event are, in some cases, overlying these buried weak layers. A human triggered avalanche in the Summit Lake area was proof of this last week. Hence, finding and triggering a slab avalanche remains a concern. 

Persistent slabs:  Buried 1-2 feet deep are facets sitting on a crust at the mid-elevations and 1-3′ deep is a buried surface hoar/facet combo at the higher elevations. The mid-elevation faceted layer seems to be the culprit for many reported ‘whumpfs’/collapses lately and is the layer responsible for the Summit Lake avalanche. Although the heart of Turnagain Pass has these layers, they are more pronounced and developed on the Southern end of Turnagain Pass and in Summit Lake where the snowpack is shallower. Areas to the North, such as Crow Pass, could also be suspect along with those that have not seen much traffic this season. Until we receive a significant load (hopefully this week), triggering these layers are becoming more and more stubborn with time. Continuing to use safe travel protocol and assessing consequences if a slab does release will be key in choosing terrain. The snowpack we have now will likely let us get away with a lot – but probably not everything. 
 

Hard wind slab on faceted snow – Summit Lake/Tenderfoot avalanche that was human triggered last Tuesday (2/27).

 

 

Valley fog up to 2,500′ limited visibility along some mid-elevations yesterday. 


 

Weather
Mon, March 5th, 2018

Partly to mostly sunny skies were found above thick valley fog yesterday; fog lingered late in the day and up to 2,500′. Ridgetop winds were light (5-10mph) from the West and North. Temperatures stayed cool, in the teens along ridgetops, but warmed up in most valley bottoms to ~30F.

Today, Monday, we can expect mostly cloudy skies with a few snow flurries in the afternoon. Only a trace of accumulation is expected. Ridgetop winds will stay light from the Northwest (5-10mph). Temperatures plummeted to the single digits last night in valley bottoms and should bounce back to the 20’sF today. Along the ridgelines, temperatures will remain in the teens.

For tomorrow, Tuesday, cloudy skies and increasing  Southeast winds will be over the area as a quick moving front moves through. Snowfall is expected Tuesday night. This flow direction is not ideal for Turnagain but we could see up to 6 inches. A series of storms will follow Tuesday night’s event, the next system moving in Thursday/Friday. Stay tuned!

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 22   0   0   67  
Summit Lake (1400′) 14   0   0   28  
Alyeska Mid (1700′) 18   0   0   60  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 16   W   7   17  
Seattle Ridge (2400′) 18   N   5   11  
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Riding Areas
Updated Wed, December 11th, 2019

Status of riding areas across the Chugach NF is managed by the Glacier and Seward Ranger Districts, not avalanche center staff. Riding area information is posted as a public service to our users and updated based on snow depth and snow density to prevent resource damage at trailhead locations. Riding area questions contact: mailroom_r10_chugach@fs.fed.us

Area Status Weather & Riding Conditions
Glacier District
Johnson Pass
Closed
Closed.
Placer River
Closed
Closed.
Skookum Drainage
Closed
Closed.
Turnagain Pass
Closed
Closed.
Twentymile
Closed
Closed.
Seward District
Carter Lake
Closed
Closed.
Lost Lake Trail
Closed
Closed.
Primrose Trail
Closed
Closed.
Resurrection Pass Trail
Closed
Closed. Will be open for the 2019/20 season pending adequate snow cover.
Snug Harbor
Closed
Closed.
South Fork Snow River Corridor
Closed
Closed.
Summit Lake
Closed
Closed.

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