Turnagain Pass Avalanche Forecast RSS

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Fri, March 22nd, 2019 - 7:00AM
Expires
Sat, March 23rd, 2019 - 7:00AM
Forecaster
Heather Thamm
The Bottom Line

The avalanche danger will remain HIGH today due to heavy rain, above freezing temperatures and strong wind in Turnagain Pass, Girdwood, and Portage. Natural wet slab avalanches are likely below 3000′. In the alpine natural storm slabs 2-3+ feet deep are also likely today and have the potential to step down into a very deep and dangerous avalanche. Travel in avalanche terrain is not recommended.

PORTAGE VALLEY: Very large avalanches have been observed in Portage over the week and are expected to continue today. Travel in avalanche terrain including runout zones, like Byron Glacier Trail is not recommended.

SUMMIT LAKE (& INTERIOR EASTERN KENAI MTS): Large avalanches have the potential to release in old buried weak layers. Natural and human triggered avalanches remain likely with the added stress of rain, new snow and wind loading today. Avoiding avalanche terrain – slopes steeper than 30 degrees and all runout zones is recommended.

SEWARD/LOST LAKE: Similar to Turnagain – warm temperatures, rain and strong winds will impact this zone today. Wet slab avalanches are likely in the mid and lower elevations and storm slabs likely in the alpine. Travel in avalanche terrain is not recommended.

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Fri, March 22nd, 2019
Alpine
Above 2,500'
High (4)
Avalanche risk
Treeline
1,000'-2,500'
High (4)
Avalanche risk
Below Treeline
Below 1,000'
High (4)
Avalanche risk
Alpine
Above 2,500'
Avalanche risk
High (4)
Treeline
1,000'-2,500'
Avalanche risk
High (4)
Below Treeline
Below 1,000'
Avalanche risk
High (4)
Danger Scale:
No Rating (0)
Low (1)
Moderate (2)
Considerable (3)
High (4)
Extreme (5)
Avalanche Problem 1
  • Wet Slab
    Wet Slab
  • Almost Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic
    Very Large
    Large
    Small
    Size
Wet Slab
Wet Slab avalanches are the release of a cohesive layer of snow (a slab) that is generally moist or wet when the flow of liquid water weakens the bond between the slab and the surface below (snow or ground). They often occur during prolonged warming events and/or rain-on-snow events. Wet Slabs can be very unpredictable and destructive.

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

Heavy rain and strong winds will remain the primary weather factors initiating a wet avalanche cycle below 2500’ today. Numerous large and very large wet slab avalanches have been releasing over the last two days and will continue through today. In some areas wet slab avalanches are taking the entire winter snowpack and leaving behind impressive piles of dirty debris. In other places, drier avalanches are releasing in the alpine and taking out the entire avalanche path – like Lipps West face seen yesterday. Many popular slopes are still intact, hanging in balance and may avalanche at any time. Today’s message is simple – stay well away from any avalanche terrain including runout zones! Wet slab avalanches are unpredictable and unsurvivable if someone was to get caught. 

Storm Slabs:
Today expect rain/snow line to fluctuate between 2000’ and 2500’. In the alpine, above 2500’ where 2-3+ feet of new snow has fallen over the last few day storm slabs are expected to be unstable. Strong Easterly winds 30-40mph and up to another 1-2’ of snow will be adding stress to the upper elevation snow pack. Natural storms slabs are likely where the snow is dry and could initiate very large avalanche in an older deeper layer of the snowpack.

South of Turnagain in the Summit Lake and areas in the interior Kenai Peninsula have a very poor snow structure with variety of old weak layers (facets and buried surface hoar) in the mid and base of the snowpack. Warm temps and rain have saturated the snowpack below 2000’ and numerous large wet slab and dry slab avalanches have released. Today up to .5” of rain is forecasted below 2500’ in the interior areas of the Kenai and with it more natural avalanche activity.

Natural avalanche on Lipps seen yesterday morning 3/21/19  

 

Many wet slab avalanches have been releasing on Seattle Ridge (SE aspect) over the last few days, but many slopes still remain intact and could release at any time. 

 

Dirty wet debris seen on the SW facing terrain of Goat Mt shoulder in Girdwood Valley. This avalanche released sometime early Thursday morning (3/21/18). Photo courtesy of G. Creighton.

 

Additional Concern
  • 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

In addition to wet slab avalanches glide cracks have been releasing over the last few days including one on Seattle Ridge and many in Girdwood Valley. Similar to wet slab avalanches these are very unpredictable and impossible to manage and another reason to avoid avalanche terrain today. 

 

 

                        New glide avalanche on a South aspect of Goat Mt in Girdwood. Photo courtesy D. Nelson

Weather
Fri, March 22nd, 2019

Yesterday: Skies were overcast and light to heavy rain was  observed throughout our region. Easterly winds were strong (30-40mph)  increasing into the 50s mph overnight and several gusts in the 100’s at ridgetops. During the day precipitation was heavier near Turnagain Arm, Portage and Girdwood Valley. Overnight intensity increased for a total of  1″ of rain in Turnagain and 1.6″ of rain at Alyeska Midway station in Girdwood. In Portage 2.27″ of rain was recorded near Bear Valley. In the alpine these water totals translate to 1-3′ of new snow. Temperatures have remained in the low-40Fs at sea level, mid-30Fs at 1000′ and rain/snow line has dropped around ~2000′.  

Today: Rain will be heavy in the morning and early afternoon with another 0.5″ – 1.5″ or rain is expected today. This is 1-2′ of snow in the alpine. Higher precipitation totals will favor Girdwood, Portage and the North side of Turnagain Pass – more coastal areas. Temperatures at sea level will be in the 40Fs and upper 30Fs at 1000′. Rain/snow line will fluctuate between 2000′ and 2500′ today.   Easterly Ridgetop winds will remain strong 30-40mph with gusts in the 50-60s mph.  

Tomorrow: Rain is expected through the weekend with lighter rain on Saturday. Coastal areas like Portage Valley will see another dose of heavy rain Saturday evening into Sunday. Temperatures will remain in the 40Fs at sea level and mid to upper 30Fs at 1000′. Rain/snow line will be around 2000′. Ridgetop winds from the East will still be elevated, 20-35 mph through Sunday morning. High pressure is in the forecast for Monday and Tuesday, but very warm above freezing temperatures will continue.  

*Seattle Ridge weather station anemometer has been experiencing some issues and may be under reporting wind data.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 36   rain   1.0   76  
Summit Lake (1400′) 38   rain 0.3   27  
Alyeska Mid (1700′) 36   rain   1.6   70  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 27   ENE   41   103  
Seattle Ridge (2400′) 32   *SE   19   75  
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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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