Turnagain Pass Avalanche Forecast RSS

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Fri, February 10th, 2017 - 7:00AM
Expires
Sat, February 11th, 2017 - 7:00AM
Forecaster
Wendy Wagner
The Bottom Line

The avalanche danger is expected to rise to CONSIDERABLE  in the Alpine by this afternoon as new snow along with wind is forecast. Wind slab avalanches up to foot or more should be easy to trigger on slopes that receive over 6-8 inches of new snow and are being loaded by winds. There is a  MODERATE avalanche danger in terrain that does not see wind loading. In these sheltered zones, including near and below treeline, watch for shallow soft slabs in the new snow as well as sluffs on steeper slopes. Additionally, there is still a chance someone could trigger a large deep slab avalanche in shallow snowpack zones.

If the snowfall forecast does not verify, the danger will remain MODERATE for shallow fresh wind slabs along ridgelines and MODERATE for triggering a deep slab avalanche.

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Fri, February 10th, 2017
Alpine
Above 2,500'
Considerable (3)
Avalanche risk
Treeline
1,000'-2,500'
Moderate (2)
Avalanche risk
Below Treeline
Below 1,000'
Moderate (2)
Avalanche risk
Alpine
Above 2,500'
Avalanche risk
Considerable (3)
Treeline
1,000'-2,500'
Avalanche risk
Moderate (2)
Below Treeline
Below 1,000'
Avalanche risk
Moderate (2)
Danger Scale:
No Rating (0)
Low (1)
Moderate (2)
Considerable (3)
High (4)
Extreme (5)
Avalanche Problem 1
  • Storm Slabs
    Storm Slabs
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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

After a nearly two week dry spell, the mountains finally had a fresh dusting of snow in most areas yesterday. Yesterday was a teaser however with only 2-4″ of very low density snow accumulating. Today, on the other hand, will hopefully be enough of a re-fresh to cover the plethora of old tracks littering the mountainsides. From this morning through tonight the National Weather service is calling for 5-9″ of low density snow. They also have a Winter Weather Advisory is in effect. 

That all said, if the snowfall forecast verifies, along with the increase in wind; ridgetop winds due to pick up to 15-20mph from the North and West. We are sure to see several shallow wind slabs, soft slabs and loose snow avalanches. The new snow from yesterday and today is falling on a very weak surface of both near surface facets and surface hoar. It will not take much wind and new snow to create very touchy wind slabs. Due to the small amounts of new snow, these slab should fairly shallow – up to a foot thick, but prevalent. 

What to watch for and keep in mind for today:

  1. How much new snow has fallen? 
  2. How is the new snow bonding with the old snow? (quick hand pits are great for assessing the old/new bonding question)
  3. Winds? Is the wind blowing snow and loading leeward slopes? (most likely to be seen above the trees and along the ridgelines)
  4. On steep slopes even a small wind slab could initiate a fast moving sluff
  5. Sluffs in the new snow are likely to be quick and gain momentum 

Surface conditions before the new snow: Surface hoar – this is now buried by 3-4″ of new snow from yesterday, with more today.

Avalanche Problem 2
  • Deep Persistent Slabs
    Deep Persistent Slabs
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.
More info at Avalanche.org

Unfortunately, we continue to find weak snow near the ground in the region (faceted snow and depth hoar). This is in a variety of layers all found in the bottom 2 feet of the snowpack. Areas with a thicker pack, such as the core slopes around Turnagain Pass, the weak snow is much stronger. But, just 5 miles down the road the pack is shallower and the weak snow is impressively weaker (as can be seen in the video below). After almost two weeks of quiet weather, these weak layers have become harder and harder to trigger as the pack has mostly adjusted. However, though the probability of triggering a deep slab avalanche is low, the consequences are high – as we have been saying for a while now. Keep that in mind along with sticking with safe travel practices.

The new snow we are getting out of the system over us now is not adding much load (only around .5 to maybe 1″ of water equivalent). However, next week’s warm stormy weather could be enough to re-active these old layers creating large dangerous avalanches. We will see. 

 

Weather
Fri, February 10th, 2017

Light snowfall covered the area yesterday adding 2-4″ of very low density snow. Skies were mostly overcast with a few ‘sucker holes’ of blue sky in the afternoon. Ridgetop winds were breeze from a North and Westerly direction (5-10mph). Temperatures were in the 15-20F range in parking lots (relatively warm) and cooling down on the ridgelines to the 10-15F range.

Today, we should see light snowfall kick up again, with another 5-9″ of low density snow accumulating by tonight – possibly more in favored areas. Ridgetop winds are expected to bump up to the 15-20mph range from the North and West. Gap winds along Turnagain Arm at sea level should be strong. Temperatures are decreasing as this cold Northerly flow pushes through – single digit temperatures are seen in valley bottoms to ridgelines with sea level zones in the mid-teensF.

The cold low-pressure system impacting us today will move out tonight and clearing skies and cold temperatures are expected for Saturday into Sunday. Sunday night into next week looks interesing – as the National Weather Service states:

  • Significant pattern changes begin this weekend as a more active southerly storm track pushes into the western Gulf. ….. The potential for some areas to receive significant snow fall followed by warming temperatures and abundant rain has the potential to make for a rather messy weather pattern.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 13   3   0.2   52  
Summit Lake (1400′) 15   2   0.1   25  
Alyeska Mid (1700′) 14   2   0.1   48  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 9   W   5   12  
Seattle Ridge (2400′) 10   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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