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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Mon, March 28th, 2016 - 7:00AM
Expires
Tue, March 29th, 2016 - 7:00AM
Forecaster
Wendy Wagner
The Bottom Line

Rain, snow and wind over the forecast region will push the avalanche hazard to CONSIDERABLE today. Wet avalanches and glide avalanches may release naturally at the mid-elevations (between 1,000′ and 2,500′). These can be large and destructive slides releasing at, or near, the ground. In the Alpine, wind slab avalanches 6-18″ thick, that are composed of the new snow, will be forming and may release naturally. Last, cornices may begin to fall with the warm conditions.  

Travel Advice:
With poor visibility expected today and the chance for large destructive slides, knowing the terrain you are traveling in is key. Simply avoid being under large slopes, runout zones and gullies.

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Mon, March 28th, 2016
Alpine
Above 2,500'
Considerable (3)
Avalanche risk
Treeline
1,000'-2,500'
Considerable (3)
Avalanche risk
Below Treeline
Below 1,000'
No Rating (0)
Avalanche risk
Alpine
Above 2,500'
Avalanche risk
Considerable (3)
Treeline
1,000'-2,500'
Avalanche risk
Considerable (3)
Below Treeline
Below 1,000'
Avalanche risk
No Rating (0)
Danger Scale:
No Rating (0)
Low (1)
Moderate (2)
Considerable (3)
High (4)
Extreme (5)
Avalanche Problem 1
  • Wet Loose
    Wet Loose
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.
More info at Avalanche.org

A fire hose of moisture is pointing our way bringing warm, wet and windy weather to most of Southcentral Alaska. In the Girdwood Valley, Turnagain Pass and Northern Kenai we are seeing light rain up to 1,500′ currently with wet snow above this. The rain/snow line is expected to rise as high as 4,000′ by tonight… If this happens it will be our highest rain line for the season. Precipitation amounts starting yesterday and ending at 6am this morning vary:

Girdwood Valley: 1.3″ water with around 10″ wet snow above 1,500′
Turnagain Pass:  Precip sensors are not reading accurately but the snow depth sensor reports 6″ of wet snow 
Summit Lake:  ~.3-.5″ water with around 4″ of snow


WET AVALANCHES: (two types)
1st type, small(ish):  As the storm warms up, rain will begin to fall on the 5-10+ inches of new snow that sits on a crust. Wet loose avalanches will be likely but smaller because they will only be composed of the new snow. Debris could run quite far however.

2nd type, much larger:  If the rain and warm temperatures soften/melt the surface crusts, water will be added to an already moist/wet snowpack at the mid-elevations. In this case we could see large wet loose and possibly wet slab avalanches. These can release deeper in the pack or near the ground creating a much larger and destructive slide.

Image below shows the warm Southerly flow that is pumping into Southcentral, AK.

 

*One of the big questions is, are we now in a “shed cycle”? This is when the snowpack becomes wet and unsupportable and literally sheds off the mountains. The answer is, maybe. It looks like this storm has potential to wet and warm the pack enough below 2,500′ (maybe even up to 3,000′) that we will start seeing large wet loose and wet slab avalanches. These could be hard to discern with the plethora of glide avalanches out there however. Although at the end of the day, it is a bit of a mess at the mid-elevations at Turnagain Pass…

Avalanche Problem 2
  • Glide Avalanches
    Glide Avalanches
Glide Avalanches
Glide Avalanches are the release of the entire snow cover as a result of gliding over the ground. Glide avalanches can be composed of wet, moist, or almost entirely dry snow. They typically occur in very specific paths, where the slope is steep enough and the ground surface is relatively smooth. They are often proceeded by full depth cracks (glide cracks), though the time between the appearance of a crack and an avalanche can vary between seconds and months. Glide avalanches are unlikely to be triggered by a person, are nearly impossible to forecast, and thus pose a hazard that is extremely difficult to manage.
More info at Avalanche.org

We could see another spike in glide avalanche activity with this warming event. Glide cracks will likely be hard to see with hampered visibility and another reason to stick to mellow terrain with nothing steep above you.

Check out this short clip of a glide avalanche caught on video in the Seattle Creek drainage on Saturday (Credit Allen Garrett). More on that avalanche report HERE. A big thanks to Allen for sending us his photos and video!

We did not see any new glide activity at the Pass yesterday but there were several noted South of Turnagain Pass as well as in Girdwood Valley. 

Additional Concern
  • 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

At elevations lucky enough to see dry(ish) snow throughout the day wind slab avalanches will be likely. How thick these will be will depend on how much snow has fallen, roughly anywhere from 6-18″. The storm will likely keep folks out of these high elevations anyhow, but a wind slab releasing from above may trigger a wet avalanche below.

Weather
Mon, March 28th, 2016

Yesterday’s weather consisted of sunny skies in the morning that were replaced by thick clouds and precipitation by the afternoon as the leading edge of a storm system moved in. Light rain has been falling to 1,000-1,500′ with wet snow above this. Ridgetop winds were strong overnight with averages in the 20-30’s and gusts to 50mph from the East.  

Today, we are expecting this warm southerly flow to continue pushing moisture our way from the Pacific. Temperatures will get warmer by the hour through tomorrow and the rain/snow line could reach the ridgetops by tomorrow night (that’s up to 4,000′). Temperature at 1,000′ should rise to the 40’s today. Between .5 and 1″ of water equivalent is expected with another ~.25-.5″ tonight. Ridgetop winds should remain strong, in the 20-30mph range with stronger gusts from the East.

Tomorrow, Tuesday, the moisture should push off to the East before another Southerly flow points our way possibly on Wednesday or Thursday.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 32   5   ??   128  
Summit Lake (1400′) 33   2   0.3   44  
Alyeska Mid (1700′) 32   10   1.3   110  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 23   NE   20   51  
Seattle Ridge (2400′) 25   SE   24   51  
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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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