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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Sun, April 8th, 2018 - 7:00AM
Expires
Mon, April 9th, 2018 - 7:00AM
Forecaster
Wendy Wagner
The Bottom Line

The avalanche danger remains  MODERATE on all aspects and  all elevations. On Northerly shaded aspects above 1,000′, human triggered dry slab avalanches 1-2′ thick are possible. On Southerly aspects, wet loose and wet slab avalanches are possible later in the day with daytime warming. If skies remain clear this afternoon, solar warming could increase significantly, increasing the chance for natural wet avalanches and cornice falls.  

Hikers and climbers in Portage Valley:  Many popular hiking areas like Byron Glacier trail and even Portage Lake have avalanche terrain above them. Avoid being under large steep slopes where wet avalanche activity is possible in the afternoon and evening.  

For the Summit Lake Summary click  HERE.  

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Sun, April 8th, 2018
Alpine
Above 2,500'
Moderate (2)
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
Moderate (2)
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
  • 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

Spring has arrived and so has the sunshine. Yesterday was the first warm sunny Saturday of the year. We had reports of relatively small wet loose avalanches on Southerly aspects and one small dry slab on a Northerly aspect (pictured below). 

Triggering a dry slab avalanche remains a concern on shady aspects. These Northerly slopes have between 8″ to 2′ of soft settled powder from last week’s snowfall. This snow fell on a variable old surface sporting everything from hard snow, facets and crusts. Bonding between the new and old snow was initially poor, but has improved over the past couple days. That said, we are still finding facets in areas under the storm snow and finding and triggering a slab avalanche remains possible. One of these was found yesterday on Tincan mentioned above. Getting your shovel out and quick hand pits are ways to help assess if the storm snow is sticking or not where you happen to be. Obvious signs on instability such as shooting cracks and whumpfing may not be present and these pockets could release further down the slope. As always, practice safe travel protocol, expose one person at a time, have escape routes planned and watch your partners. 
 

Deep Persistent Slabs:  Buried in the middle and toward the bottom of the snowpack are old weak layers of facets and buried surface hoar. These layers formed in January and though they have not been responsible for avalanche activity for over a month or more, the springtime warm up can re-activate old layers. Although very unlikely an avalanche will release in these, it’s good to remember our snowpack has a poor structure. Most concerning areas are those with a thin snow cover such as the Girdwood Valley and the South end of Turnagain Pass and Summit Lake.

 

 Small slab avalanche triggered remotely on Tincan’s Notherly aspect.


Avalanche Problem 2
  • Wet Loose
    Wet Loose
  • Almost Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic
    Very Large
    Large
    Small
    Size
Wet Loose
Wet Loose avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.

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

Wet avalanche activity will again be a concern later in the day on sunlit aspects. Several wet loose avalanches were seen yesterday both natural and human triggered. All these we know of were generally small and easily avoided. Today will likely be a similar scenario. Temperatures are warm this morning at the higher elevations and even with clouds expected later today, the surface crusts are likely to soften. Once the sun crust melts and the snow becomes wet and ‘punchy’ to your boot, it’s time to head to more shaded slopes. Even a small wet snow avalanche can push you around somewhere you don’t want to go.

Wet Slabs: We have not seen any confirmed wet slab avalanche activity yet, but this could be just around the corner. There was a natural slab avalanche on a Westerly aspect in Portage Valley noted yesterday. We don’t have quite enough details, but this could be a sign wet slabs may begin to occur if warm days continue. 

 Wet loose avalanches on Pete’s South, on the Southerly end of Turnagain Pass. 

 

Slab avalanche seen yesterday in Portage Valley 

Weather
Sun, April 8th, 2018

Sunny skies were over the region yesterday. Temperatures climbed into the mid 40’s F at 1,000′ and  near 30F along the ridgetops. Overnight, valley bottoms have cooled into the upper 20’s F while warm air streaming in aloft has kept ridgetop temperatures warm. In fact, the Sunburst weather station  has jumped from 27F to 32F since midnight. Ridgetop winds were light from the Northwest, in the 5-10mph range, during the day before shifting Easterly along with the warm air moving in around midnight.  

Today, clear skies are expected this morning before cloud cover moves in later in the day. This is associated with a low pressure spinning in the Gulf slowly moving our way. There is a chance for a few snow flurries tonight, adding a trace of new snow (with light rain below 1,500′). Ridgetop winds will remain Easterly in the light to moderate range (5-15mph). Temperatures will again be warm. Ridgetops should see high temperatures in the 30-35F range while valley bottoms warm to the upper 40’sF.  

For Monday and Tuesday, the low pressure system in the Gulf will move in and should keep skies mostly cloudy. There will be a chance for a few inches of new snow above 2,000′ and light rain below as temperatures remain spring-like.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 35   0   0   80  
Summit Lake (1400′) 34   0   0   33  
Alyeska Mid (1700′) 35   0   0   77  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 28   W   7   20  
Seattle Ridge (2400′) 32   NW   5   14  
Observations
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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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