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ARCHIVED - Forecasts expire after 24 hours.
Issued
Wed, January 17th, 2024 - 7:00AM
Expires
Thu, January 18th, 2024 - 7:00AM
Forecaster
Mik Dalpes
Avalanche risk The Bottom Line

The avalanche danger is CONSIDERABLE above 2,500’ as an outflow wind event blows through the region. It will be likely for a person to trigger an avalanche 1-2’ deep in freshly windblown snow. Natural wind slab avalanches will also be possible in the higher terrain. Additionally, glide avalanches remain a concern above 1,000’ where the avalanche danger is MODERATE. We recommend moving quickly and one at a time below glide cracks if there is no alternate route. Below 1000′ the avalanche danger is LOW. 

Summit Lake / Seward / Lost Lake: These areas, especially Seward, are seeing higher winds with this outflow event creating more dangerous avalanche conditions.

Special Announcements

Girdwood Forecaster Chat – Friday, Jan 19th! Andrew Schauer will be discussing the different shades of MODERATE danger at the Girdwood Brewing Co. (6:30pm Jan 19). What does “spicy moderate” mean? More details HERE.

 

Wed, January 17th, 2024
Alpine
Above 2,500'
3 - Considerable
Avalanche risk
Treeline
1,000'-2,500'
2 - Moderate
Avalanche risk
Below Treeline
Below 1,000'
1 - Low
Avalanche risk
Thu, January 18th, 2024
Alpine
Above 2,500'
2 - Moderate
Avalanche risk
Treeline
1,000'-2,500'
2 - Moderate
Avalanche risk
Below Treeline
Below 1,000'
1 - Low
Avalanche risk
Thu, January 18th, 2024
Alpine
Above 2,500'
2 - Moderate
Avalanche risk
Treeline
1,000'-2,500'
2 - Moderate
Avalanche risk
Below Treeline
Below 1,000'
1 - Low
Avalanche risk
0 - No Rating
1 - Low
2 - Moderate
3 - Considerable
4 - High
5 - Extreme
Avalanche risk Avalanche risk Avalanche risk Avalanche risk Avalanche risk
Travel Advice Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features. Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern. Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding, and conservative decision-making essential. Very dangerous avalanche conditions. Travel in avalanche terrain not recommended. Extraordinarily dangerous avalanche conditions. Avoid all avalanche terrain.
Likelihood of Avalanches Natural and human-triggered avalanches unlikely. Natural avalanches unlikely; human-triggered avalanches possible. Natural avalanches possible; human-triggered avalanches likely. Natural avalanches likely; human-triggered avalanches very likely. Natural and human-triggered avalanches certain.
Avalanche Size and Distribution Small avalanches in isolated areas or extreme terrain. Small avalanches in specific areas; or large avalanches in isolated areas. Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas. Large avalanches in many areas; or very large avalanches in specific areas. Very large avalanches in many areas.
Recent Avalanches

No new avalanches have been reported in Turnagain Pass since Sunday, January 14, although new glide cracks are reported daily. However, four new glide avalanches were reported elsewhere. Two in Girdwood Valley; one on Raggedtop and the other in the upper Crow Creek drainage. The other two were in the Summit Lake zone on the east face of Fresno and the south face of Wilson North.

Avalanche Problem 1
  • Wind Slabs
    Wind Slabs
  • Aspect/Elevation
  • Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
    Size
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.

Aspect/Elevation of the Avalanche Problem
Specialists develop a graphic representation of the potential distribution of a particular avalanche problem across the topography. This aspect/elevation rose is used to indicate where the particular avalanche problem is thought to exist on all elevation aspects. Areas where the avalanche problem is thought to exist are colored grey, and it is less likely to be encountered in areas colored white.

Likelihood of Avalanches
Terms such as "unlikely", "likely", and "certain" are used to define the scale, with the chance of triggering or observing avalanches increasing as we move up the scale. For our purposes, "Unlikely" means that few avalanches could be triggered in avalanche terrain and natural avalanches are not expected. "Certain" means that humans will be able to trigger avalanches on many slopes, and natural avalanches are expected.

Size of Avalanches
Avalanche size is defined by the largest potential avalanche, or expected range of sizes related to the problem in question. Assigned size is a qualitative estimate based on the destructive classification system and requires specialists to estimate the harm avalanches may cause to hypothetical objects located in the avalanche track (AAA 2016, CAA 2014). Under this schema, "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. "Very Large" avalanches may bury or destroy vehicles or houses, and "Historic" avalanches are massive events capable of altering the landscape.

Signal Word Size (D scale) Simple Descriptor
Small 1 Unlikely to bury a person
Large 2 Can bury a person
Very Large 3 Can destroy a house
Historic 4 & 5 Can destroy part or all of a village
More info at Avalanche.org

The northwest winds were strong enough last night to form fresh wind slabs in the upper elevations. These outflow winds are forecast to remain elevated through the day blowing 15-25 mph and gusting to 40 mph in the Turnagain Pass area. Stronger winds are forecast in the Crow Pass area of Girdwood Valley and to the south at Summit Lake and Seward. Wind direction can vary with this flow pattern. Typically, Seattle Ridge sees northwest wind and winds on Sunburst come from the south, but this isn’t always the case.

If the wind forecast verifies today wind slabs will be easy to trigger in the upper elevations. How sensitive these slabs are to trigger will depend on how recently the slab formed and how well it is bonding to the snow beneath. To assess the conditions, watch for recent avalanches and snow blowing off ridgelines and across gully’s depositing into pillow-like features. Wind affected snow feels firm beneath your machine or feet and may sound hollow or produce a shooting crack.

This outflow wind event is impacting a large area of Alaska. It looks like Turnagain Pass will be spared from the strongest winds. Image courtesy of the NWS Anchorage office 1.17.24.

Avalanche Problem 2
  • Glide Avalanches
    Glide Avalanches
  • Aspect/Elevation
  • Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
    Size
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.

Aspect/Elevation of the Avalanche Problem
Specialists develop a graphic representation of the potential distribution of a particular avalanche problem across the topography. This aspect/elevation rose is used to indicate where the particular avalanche problem is thought to exist on all elevation aspects. Areas where the avalanche problem is thought to exist are colored grey, and it is less likely to be encountered in areas colored white.

Likelihood of Avalanches
Terms such as "unlikely", "likely", and "certain" are used to define the scale, with the chance of triggering or observing avalanches increasing as we move up the scale. For our purposes, "Unlikely" means that few avalanches could be triggered in avalanche terrain and natural avalanches are not expected. "Certain" means that humans will be able to trigger avalanches on many slopes, and natural avalanches are expected.

Size of Avalanches
Avalanche size is defined by the largest potential avalanche, or expected range of sizes related to the problem in question. Assigned size is a qualitative estimate based on the destructive classification system and requires specialists to estimate the harm avalanches may cause to hypothetical objects located in the avalanche track (AAA 2016, CAA 2014). Under this schema, "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. "Very Large" avalanches may bury or destroy vehicles or houses, and "Historic" avalanches are massive events capable of altering the landscape.

Signal Word Size (D scale) Simple Descriptor
Small 1 Unlikely to bury a person
Large 2 Can bury a person
Very Large 3 Can destroy a house
Historic 4 & 5 Can destroy part or all of a village
More info at Avalanche.org

The glide avalanche problem continues with new glide cracks reported daily throughout the forecast areas. Pictured below is the very large avalanche that released on Sunday, January 14 above the Seattle Ridge motorized up track. There are still several open cracks that could avalanche onto the up track itself and other cracks that loom above other well traveled areas. Avoid traveling underneath glide cracks when possible. When an alternate route isn’t an option, we recommend making a plan before traveling underneath glide cracks. This plan includes identifying safe spots to stop and group up, watching the slope above while traveling one at a time and moving quickly. These avalanches are large and destructive as they take the entire 5-7’ of snowpack with them.

Very large glide avalanche just to the left of the main Seattle Ridge motorized up track. There are still many glide cracks capable of avalanching onto the up track itself. Photo 1.15.24

Additional Concern
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

There is an old weak layer (near surface facets and buried surface hoar) that was causing avalanches over a week ago; last known was Monday 1/8. It sits around 2-4′ deep in the snowpack, is hard to find, and showing signs that it has bonded, all good news. We will be taking this issue off the forecast but will still be watching for it behind the scenes. We’d like to remind folks headed to less traveled areas to always be aware an outlier avalanche is possible. These areas include Lynx Ck/Bench Pk zone and Silvertip.

Weather
Wed, January 17th, 2024

Yesterday: The temperature inversion continued yesterday with temperatures in the single digits at road level and upper 20’s F to 33F along ridgetops. Skies were mostly clear with some valley fog in places. Ridgetop winds picked up yesterday afternoon from the northwest averaging 5-20mph gusting up to 40 mph overnight. Winds at Summit Lake were similar to Turnagain with stronger winds in Seward.

Today: High pressure continues to strengthen bringing clear skies, cold arctic air, and strong northwest winds through the gaps in terrain. This is a widespread outflow event with the highest winds expected today especially in places like Thompson Pass, Turnagain arm, and Seward. Turnagain Pass looks to be sheltered from the strongest winds with 15-20 mph and gusts to 40 mph expected. Temperatures are forecast to be 10-15 degrees F.

Tomorrow: Gap winds should decrease slightly overnight tonight and by tomorrow afternoon winds look light and variable. Skies should remain clear and temperatures in the low teens F.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 21 0 0 82
Summit Lake (1400′) 12 0 0 63
Alyeska Mid (1700′) 19 0 0 77
Bear Valley – Portage (132′) 12 0 0

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 26 W 10 27
Seattle Ridge (2400′) 26 W 4 25
Observations
Recent Observations for Turnagain Pass
Date Region Location
02/24/24 Turnagain Observation: TinCan Backdoor/ Center Ridge
02/22/24 Turnagain Avalanche: Lynx Creek
02/22/24 Turnagain Observation: Turnagain, Seattle, Mt Ascension
02/21/24 Turnagain Observation: Tincan Trees
02/21/24 Turnagain Observation: Sunburst
02/20/24 Turnagain Avalanche: Tincan
02/20/24 Turnagain Observation: Seward Highway across from Johnson Pass TH
02/19/24 Turnagain Avalanche: Base of Seattle Ridge
02/18/24 Turnagain Observation: Lynx creek
02/18/24 Turnagain Observation: Tincan Trees
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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.