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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Sun, April 15th, 2018 - 7:00AM
Expires
Mon, April 16th, 2018 - 7:00AM
Forecaster
Heather Thamm
The Bottom Line

The avalanche danger is  LOW  this morning and will rise to  MODERATE  in the afternoon. Triggering a small to large wet avalanche will be possible with daily warming on sunlit aspects.  In the Alpine, triggering a slab avalanche 1-2′ thick remains possible above 3000′ on shaded aspects in areas where the snowpack is generally thinner. Give cornices extra space.  

MONDAY AVALANCHE OUTLOOK:
No avalanche forecast will be issued tomorrow, Monday April 16th. The avalanche outlook will be the same message tomorrow as for today due to a similar weather pattern in the forecast.  

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Sun, April 15th, 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 corn cycle has finally arrived and with it a potential for wet loose activity in the afternoons. Several nights of clear skies and freezing temperatures have formed a supportable crust adding strength to the snow in the mornings. As the day heats up and the crust melts and loses strength, the danger rises – making it possible to trigger a wet avalanche on steep sun exposed terrain features. Today’s weather looks similar to yesterday with temperatures expected to reach the mid 40F’s by early afternoon. Remember solar noon is around 2pm and warm wet snow surfaces will last through the early eveningObservations over the last two days have found the weakest wet snow conditions below 2500’ on very steep East to South aspects. There is more potential for wet snow to entrain a larger avalanche in this elevation band. Don’t let this catch you off guard if you start out in the upper elevations and the snow quickly changes as you descend. Pay attention to surface crusts as they break down and become moist. When the snow becomes wet and ‘mushy’ and your skis or snowmachine track start trenching into wet snow, it’s time to find supportable surfaces. Even a small wet avalanche could be hard to manage especially in a terrain trap. As we move away from a rain event that occurred mid-week, and water drains out of the snow, it’s becoming less likely for someone to trigger a wet slab. 

Cornices: Daily warming and sunnier weather can make cornices more unstable. As always, give cornices plenty of space and limit exposure underneath them.

A melt/freeze crust exists on shaded Northern aspects to ~3000′ and was not warming by mid afternoon on Tincan. South aspects had 3-5″ of wet surface snow the alpine mid day. 

 

East and South aspects have been warming significantly over the last few days. Note the shiny look of the East aspects in Lynx Creek area. 

 

Additional Concern
  • Persistent Slabs
    Persistent Slabs
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.
More info at Avalanche.org

Triggering a lingering storm slab or a persistent slab 1-2’ deep is becoming less likely with time. Old weak snow (facets) buried within the top 2’ of the snowpack have been found in the upper elevations over the last few weeks. Northerly aspects above 3000’ with dry snow may harbor this set up. So far there have been no reports of any avalanche activity on these shaded slopes following the mid-week storm that ended Wednesday. However the periphery of our forecast zone is more suspect, Crow Pass area and Johnson Pass to Summit Lake, where a thinner (weaker) snowpack remains. Before committing to steeper slopes in the upper elevations, take a moment to evaluate the terrain for consequences should a slab release.  

Weather
Sun, April 15th, 2018

Yesterday was clear and sunny and no precipitation was recorded. Temperatures reached the low 50F’s near sea level and mid 40F’s in the mid elevations. Ridgetops were in the mid to low 30F’s during the heat of the day. Overnight temperatures dropped into the upper 20Fs to low 30F’s. Winds were light (5-15mph) from the West.

Today will be similar with sunny skies and another warm day on tap. Temperatures should again reach the low 50F below 1000′ and mid 30F’s in the upper elevations. Winds will be light (0-10mph) from the Southeast. Overnight temperatures should drop into the upper 20F’s to low 30F’s.  

Monday and Tuesday look to be a mix of partly cloudy to partly sunny weather with a slight chance for a few snow flurries. If we see precipitation it will be minimal. Daytime temps are expected to be in the mid 40F’s and overnight lows in the upper 20F’s. Winds are expected to be light. Wednesday into the Thursday there is a chance for precipitation (rain and snow) as low pressure moves through the Gulf of Alaska. At this point coastal areas look to be the most impacted.  

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 40   0   0   67  
Summit Lake (1400′) 35   0   0   24  
Alyeska Mid (1700′) 38   0   0   63  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 29   WNW   6   17  
Seattle Ridge (2400′) 35   WNW   7    25
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Riding Areas
Updated Mon, December 02nd, 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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