Support the forecast! Support the forecast!

Give to Friends of the Chugach National Forest Avalanche Info Center.

Turnagain Pass Avalanche Forecast RSS

Archives
ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Tue, February 18th, 2020 - 7:00AM
Expires
Wed, February 19th, 2020 - 7:00AM
Forecaster
Ryan Van Luit
Avalanche Warning
Issued: February 18, 2020 6:00 am
Travel in avalanche terrain is not recommended. Avoid being on or beneath all steep slopes.
The Bottom Line

We have issued a BACKCOUNTRY AVALANCHE WARNING through the National Weather Service for the Turnagain Pass area and surrounding mountains.

Heavy snowfall, rain, and strong winds have created a HIGH avalanche danger in the mountains surrounding Turnagain Pass, Girdwood Valley, Portage Valley, and areas on the Kenai including Summit Lake and the Seward zone. Dangerous avalanche conditions are expected on all slopes 30 degrees and steeper – including runout zones. Avalanches are expected to release naturally, be easily triggered by people and send debris to valley floors. Travel in avalanche terrain is NOT recommended. Areas with steep slopes above should be avoided, such as the Byron Glacier Trail and the Seattle Ridge Uptrack. Even small terrain features could act as deadly traps.

SUMMIT LAKE TO SEWARD REGION: Expect the avalanche danger to remain elevated due to warm temperatures, strong winds and recent precipitation.

*Roof Avalanches:  Warming temperatures and rain could cause roofs to begin to shed their snow. Pay special attention to children, pets and where you park your car.

Special Announcements

Increased avalanche danger exists region-wide, outside of our forecast area. Very strong wind was seen overnight and the NWS has issued a winter storm warning for Chugach State Park through tomorrow morning.

Thanks to our sponsors!
Tue, February 18th, 2020
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
  • 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

In the last 24 hours temperatures have increased to above freezing, pushing our snow line to 1300′.  The mountains around Girdwood have seen over 1″ of storm water in this time while Turnagain pass is showing 0.3″ of storm water.  These numbers could translate to 12-24″ of snow where it’s cold enough to accumulate.  We’re expecting up to another 1″ of storm water, which could mean an additional 12-24″ of snow in the Alpine in the coming 24 hour period.

When we add these warm temperatures and precipitation with steady winds ranging from 20-40mph gusting up to 83mph, we’ll have storm snow issues, wet avalanches concerns, and large wind slabs developing.

Natural activity is expected throughout the day with continued weather impacting our region. This includes large natural slab avalanches 2-5’ thick in the alpine and wet avalanches below 2000’ due to heavy rain and above freezing temperatures. Avalanche activity could run the full length of a slope, thus it will be important to stay off any slopes greater than 30 degrees and avoid being near any runout zones today. This set up could be a hazard even in the Tincan Trees where small terrain features could have high consequences. In channeled terrain an avalanche from above could easily entrain wet snow in the lower elevations and run further than expected. This will be especially important in places like Portage Valley, Johnson Pass trail and the flats below Seattle Ridge.

Avoidance of avalanche terrain is the only way to “manage” this problem today.  It’s a great day to hit the slopes of Alyeska, or do your taxes!

Avalanche Problem 2
  • 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

Weak layers of facets and buried surface hoar within the snowpack continue to be a concern throughout the region.  With new snow accumulating over the existing snowpack, the region-wide Persistent Slab is transitioning into a Deep Persistent Slab. Significant weak layers now sit at least 3′ deep in the snowpack in many places.  Will this new load of snow and rain tip the balance and cause widespread avalanches?  Today avalanches occurring in the upper layers of storm snow have the potential to step down and release deeper layers. If this does happen the volume will be large and could run long distances.

Travel in avalanche terrain is not recommended today including being in the runout of a steep slope.

Weather
Tue, February 18th, 2020

Yesterday: Cloudy skies with 5-10″ of snow accumulation overnight.  Winds were easterly at 20-30 mph gusting into the 50s. Temperatures ranged from the low 30°Fs to the high teens. Winds and precipitation intensity increased overnight and temperatures climbed into the 20°Fs and 30°Fs. An inch of storm water (10-12″ of snow) was recorded with rain at sea level and as high as 1000-1300′.

Today: Heavy snow and rain continue today into tomorrow with a snow line forecast at 1300′. Additional snow accumulations ranging from 12-24″ are expected in the Alpine.  Winds will remain strong in the morning and slowly diminish later in the day.  Temperatures at sea level will hover in the 30°Fs to low 40°Fs during the day and shift into the upper 20°Fs in the evening.

Tomorrow: Tuesdays storm is expected to taper by tomorrow before the next storm picks up Wednesday evening.  Temperatures are likely to cool into the 20°Fs with southerly winds ranging from 10-30mph.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 32 3 0.33 64
Summit Lake (1400′) 33 2 0.3 26
Alyeska Mid (1700′) 29 8 1.1 68

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 20 ENE 37 83
Seattle Ridge (2400′) 25 SE 18 35
Observations
Recent Observations for Turnagain Pass
Date Region Location
02/18/20 Turnagain Observation: Tin Can
02/17/20 Turnagain Observation: Cornbiscuit
02/16/20 Turnagain Avalanche: Eddies, Sunburst, Cornbiscuit
02/16/20 Turnagain Observation: Sunburst
02/16/20 Turnagain Observation: Pete’s North
02/16/20 Turnagain Avalanche: Sunburst
02/16/20 Turnagain Observation: Eddies upper peak
02/15/20 Turnagain Observation: Eddies
02/15/20 Turnagain Observation: Tincan
02/15/20 Turnagain Observation: Wolverine north shoulder
Riding Areas
Updated Thu, January 30th, 2020

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
Open
Placer River
Open
Skookum Drainage
Open
Turnagain Pass
Open
Twentymile
Open
Open to over snow travel on 1/22.
Seward District
Carter Lake
Open
Lost Lake Trail
Open
Open to over snow travel on 1/22. Please stay on trail to prevent resource damage
Primrose Trail
Open
Open to over snow travel on 1/22. Please stay on trail to prevent resource damage.
Resurrection Pass Trail
Open
Open for the 2019/2020 winter season.
Snug Harbor
Open
South Fork Snow River Corridor
Open
Open as of 1/30
Summit Lake
Open

Subscribe to Turnagain Pass
Avalanche Forecast by Email

This is a general backcountry avalanche advisory issued for Turnagain Arm with Turnagain Pass as the core advisory area. This advisory does not apply to highways, railroads or operating ski areas.