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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Fri, April 13th, 2018 - 7:00AM
Expires
Sat, April 14th, 2018 - 7:00AM
Forecaster
Wendy Wagner
The Bottom Line

The avalanche danger is LOW this morning and will rise to  MODERATE  today for wet avalanches on sunlit slopes. If there are slopes that did not have a solid re-freeze last night, natural wet avalanches are possible and the danger could rise to CONSIDERABLE.    In the Alpine, triggering a slab avalanche around a foot thick remains possible where drier snow exists. Give cornices a wide berth.

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Fri, April 13th, 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
  • 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

The snowpack is heating up and beginning to slide off the mountain sides. Not everywhere, but the usual suspects have seen large wet avalanches over the past couple days, with the majority of the activity two days ago on Wednesday. Pyramid’s West face and the Southeast facing aspects of Seattle Ridge are these suspects and true to tradition, these slopes have seen the majority of the action. Although we have likely gone through the peak of acitivity for this first ‘warm-up’, any steep slope with a more shallow snowpack and baking in the sun is a concern for a naturally occurring large wet avalanche. 

For those headed out today, and this weekend, timing is everything. This morning, it’s likely that the wet surface snow has undergone a fairly solid re-freeze and the avalanche danger is LOW. As the day heats up and the crusts melt and lose strength, the danger rises. This is when wet avalanches can begin to release, either naturally or by a person. Remember solar noon is around 2pm so the snowpack is the warmest, and most dangerous, from ~1pm till ~5pm. Once snow becomes wet and ‘mushy’ up to you boot top, or your track starts trenching in wet snow, it’s time to head to a more supportable surface. Even a small wet avalanche can turn into something larger in bigger terrain. 

Photo below is on one example of the many large wet loose/wet slab avalanches on the Southeast face of Seattle Ridge occurring Wednesday.

 

Wider angle view of Seattle Ridge and the many large wet avalanches from Wednesday.

 

 
Large wet loose slides from Tuesday on the East face of Pyramid.

 

The West face of Pyramid continues to shed its snowcover as the days go by. Note the slabs on the lower looker’s left of photo – these occurred sometime Wednesday evening/Thurs morning.


Avalanche Problem 2
  • Storm Slabs
    Storm Slabs
  • Almost Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic
    Very Large
    Large
    Small
    Size
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.

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

Triggering a dry(ish) slab avalanche is still possible and occurred yesterday. A skier was caught and carried in a slab around a foot deep in the Johnson Pass zone. Skier was ok. This slope was at 4,900′ on a West aspect. 

Upper elevation zones (above 3,500′) received up to a foot of new snow on Tues/Wed this week while light rain fell down low. This 8-12″ of snow is sitting on predominantly sun crust on E, S and West aspects. If you are in these higher elevation areas, such as near Whittier, Bench Peak, etc., watch for any new snow to become moist and possibly slide on the slick sun crust underneath. Hence, triggering a dry slab avalanche is still possible at the upper elevations. 

Weather
Fri, April 13th, 2018

Yesterday, sunny skies with light Easterly winds were over the region. Temperatures climbed to the low 50’sF at 1,000′ and to the upper 30’sF along the higher ridgelines at 4,000′. Overnight, a few clouds have moved in and temperatures have dropped to the 30’sF across the board – from ridgetops to sea level.  

For today, most sunny skies and another warm day are forecast. Temperatures should again reach 50F at 1,000′ at Turnagain Pass, mid 50’sF at sea level and just under 40F along ridgelines. Ridgetop winds will remain light (5-10mph) from the East before slowly shifting Northerly by tonight.  

For the weekend, sunny and blue skies will be over the region. Ridgetop winds at this time are expected to be light and Northerly bringing in slightly cooler air. Temperatures should be on a textbook durnal trend with cooling overnight and warming during the day. Models are suggesting the possibility for light rain Monday into Tuesday associated with a low-pressure developing near the Aleutians.  

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 40   0    0 69  
Summit Lake (1400′) 42   0   0   25  
Alyeska Mid (1700′) 41   0   0   66  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′)  31 E   8   28  
Seattle Ridge (2400′) 35   E   10   27  
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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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