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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Mon, March 26th, 2018 - 7:00AM
Expires
Tue, March 27th, 2018 - 7:00AM
Forecaster
Wendy Wagner
The Bottom Line

The avalanche danger continues to be  MODERATE  above 1000′ where triggering a hard slab avalanche 2-4+ feet thick is possible. These hard slabs could be found on all aspects and may be remotely triggered from the side or below. Additionally, watch for old wind slabs along ridgelines and give cornices a wide berth.  

Poor snowpack structure exists at Summit Lake and hard slab avalanches remain a concern there as well. Check out the most recent  Summit snowpack and avalanche summary  if you are headed South of Turnagain Pass.

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Mon, March 26th, 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
  • Deep Persistent Slabs
    Deep Persistent Slabs
  • Almost Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic
    Very Large
    Large
    Small
    Size
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.

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

As we enter the last week of Marvelous March, we are in a holding pattern of sorts avalanche-wise. The snowpack structure remains poor. Various weak layers in the middle and the base of the pack are persisting, keeping the avalanche danger at MODERATE for triggering a hard slab avalanche 2-4 feet thick. As time passes, the likelihood of triggering one of these dangerous avalanches is decreasing, but with the high consequences conservative terrain choices continue to be recommended. Many folks are taking advantage of the hard-pack snow conditions by long tours and exploring. With this however, keep in mind this avalanche problem is tricky and triggering a slab from the flats below a slope is possible. Being aware of runout zones and considering how far an avalanche could send debris should be in the forefront of our minds this spring.

In case you are just tuning in, our problem layers are from January. They are facets sitting on a slick melt/freeze crust at the mid elevations and facets mixed with buried surface hoar at the upper elevations. The slab on top is 2-4′ thick and very hard due to a strong Northwest wind event that ended last Thursday. This wind event caused unusual loading patterns and created a situation where the typical windward slopes (thinner weaker snow) are more loaded and avalanches could be triggered in unexpected places. To show this, observers have found poor structure along scoured ridges and under sastrugi. The last avalanche we know of was Friday (three days ago) in the Girdwood Valley and was remotely triggered from 200 yards away

*Keep in mind that the snowpack may not show any obvious signs before the slope releases. It may be the 10th skier or snowmachiner onto a slope that finds a thin part of the snowpack (a trigger point). It is always good for us to take a moment and visualize the consequences if the slope are exposed to does slide. 

 

This photo is looking up at the Southwest face of Sunburst. This old avalanche was triggered exactly two weeks ago today after the last snowfall event. On that Monday, a storm ended that brought 2-3′ of new snow to Turnagain. This snow has now settled to around a foot or less and experienced much wind and sun damage over the past two weeks.

Pastoral Peak on the left and Kickstep on the right. The mountains look deceptively stable with a hard wind and sun affected surface.


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

Wind Slabs:  Old hard wind slabs may be lurking on a variety of aspects due to prior unusual loading patterns. Steep rocky terrain, where slabs sit on unsupported slopes, are the most suspect for triggering a wind slab. This type of terrain is also suspect for triggering a deeper slab mentioned above. 

Cornices: Cornices are large in places and the sun and above freezing temperatures can make them more unstable. Give cornices plenty of space and limit exposure underneath them.

Weather
Mon, March 26th, 2018

Sunny skies again filled the region yesterday before cloud cover moved in during sunset. The anticipated snow flurries never developed. Ridgetop winds remained Easterly in the 10-20mph range with the strongest recordings early this morning, gusting to the mid 30’s mph. Temperatures have remained in the teens along ridgetops during the past 24-hours but cloud cover has kept valley bottoms warm where stations are reporting 25-30F temperatures this morning.

Today, Monday, expect overcast skies, cool temperatures and moderate ridgetop Easterly winds. There is a chance a few snow flurries could make it down to the ground, but this is more likely on the Southern and Eastern most part of the Kenai Peninsula. Temperatures look to remain in the teens along ridgetops today with valley bottoms hovering in the mid 30’sF. Ridgetop winds are expected to remain in the 10-20mph range from the East.  

For Tuesday and into Wednesday, a front moves through Western Alaska and may bring a light snow to Southcentral. There is much uncertainty as to this system, yet it doesn’t look like the Turnagain Pass area will see much snowfall, mainly cloud cover at this point.  

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 26   0   0   79  
Summit Lake (1400′) 25 0   0   32  
Alyeska Mid (1700′) 27   0   0   73  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 17   NE   12    34
Seattle Ridge (2400′) 23   ESE   17     34  
Observations
Recent Observations for Turnagain Pass
Date Region Location
12/10/19 Turnagain Avalanche: Tincan and Sunburst from the air
12/10/19 Turnagain Observation: Tincan
12/08/19 Turnagain Avalanche: Tincan
12/06/19 Turnagain Avalanche: Sunburst
12/04/19 Turnagain Observation: Sunburst
12/03/19 Turnagain Observation: Hippy Bowl
12/01/19 Turnagain Observation: Tincan, All elevations
12/01/19 Turnagain Observation: Tincan
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11/29/19 Turnagain Observation: Sunburst Ob #2
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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