Turnagain Pass RSS

Archives
ARCHIVED - Forecasts expire after 24 hours.
Issued
Sat, April 30th, 2022 - 7:00AM
Expires
Sun, May 1st, 2022 - 7:00AM
Forecaster
Andrew Schauer
Avalanche risk The Bottom Line

The avalanche danger will rise to CONSIDERABLE as stormy weather starts to pick up during the day. Strong winds and increasing snowfall will make it likely a person will be able to trigger a wind slab avalanche up to a foot deep by the end of the day at higher elevations. Pay close attention to changing conditions, and move to lower slope angles once the storm picks up and you start seeing signs of unstable snow. Lower elevations saw little or no refreeze overnight and will likely get rain on snow later today, making wet avalanches possible. This includes wet loose, wet slab, and glide avalanches. Avoid traveling on or below steep terrain if you notice wet and unsupportable snow.

SUNDAY AVALANCHE OUTLOOK: The storm is expected to pick up overnight and continue into tomorrow, with over a foot of new snow possible at Turnagain Pass and Girdwood, and 2-3′ possible in the Portage and Placer Valleys. Expect increasing avalanche danger, especially in the areas with the heaviest snowfall. This is our final advisory of the season. We will post our springtime tips tomorrow morning, but that will not include a danger rating.

Special Announcements
  • Valdez Avalanche Fatality: We are sad to share the news of a fatal accident in Valdez on Monday, April 25. A ski guide triggered an avalanche, deployed an avalanche airbag, and was carried approximately 1500 vertical feet. The avalanche ran over a cliff, and the skier did not survive. Our deepest condolences go out to the victim’s friends and family. He was a long time ski guide and a well respected member of the community. This is a heavy loss for the Alaskan snow community, and he will be missed. There is some preliminary information in this article from ADN.
  • End of Season Operations:  Today is our final forecast for the season. We will post our springtime tips tomorrow morning. We will continue to publish observations as they come in, and will use our social media channels periodically to post pertinent info. Thank you to everybody for another great season, and have a fun and safe spring and summer!
Sat, April 30th, 2022
Alpine
Above 2,500'
3 - Considerable
Avalanche risk
Treeline
1,000'-2,500'
3 - Considerable
Avalanche risk
Below Treeline
Below 1,000'
3 - Considerable
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.
Avalanche Problem 1
  • Wind Slabs
    Wind Slabs
  • 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.
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

Stormy conditions are returning to the area, with increasing winds this morning ahead of a round of precipitation that could bring over a foot of new snow to Turnagain Pass and Girdwood and 2-3′ to Portage and Placer by tomorrow morning. The avalanche danger is expected to rise as the storm progresses, and today the main factor determining stability will be the timing of the storm. Winds are currently blowing 10-20 mph out of the east with gusts to 45 mph, but are expected to pick up to 20-40 mph during the day. While the most intense precipitation will likely be overnight, we can still expect to see 3-5″ snow by the end of the day today with slightly more in Portage and Placer. Combined with the strong winds, this will be enough to make human-triggered avalanches up to a foot deep likely, especially in the upper elevations.

Today it will be important to pay attention to changing conditions and increasing danger as the storm unfolds. The most dangerous areas will be those that are getting the most snow. Avoid slopes seeing active wind loading, and move to lower angle terrain if you see any shooting cracks, fresh avalanche activity, or are experiencing any collapses.

Cornices: Strong winds and new snow will continue to build cornices and push them closer to their breaking point. Be sure to give them plenty of space while traveling along ridgelines, and limit time spent traveling under them.

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Avalanche Problem 2
  • Wet Slab
    Wet Slab
  • Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
    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
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 approaching storm is expected to bring rain up to 1500′ today, with rising rain levels tonight and tomorrow. Combined with a little or no overnight refreeze last night, this will make wet avalanches possible. We have seen some very large wet slabs releasing over the past week, and these things are nothing to mess with. Avoid traveling on or below steep terrain if you are noticing sloppy, unsupportable snow at the surface. The rain on snow will make avalanches possible on all aspects– unlike the recent activity, which has been mostly confined to easterly and southerly slopes. The size of some of these avalanches is downright scary, and is worth considering before traveling on or below any steep terrain.

Glide Avalanches continue to release across the area. These are large, destructive, and unpredictable. Avoid spending time under glide cracks, which open up before glide avalanches release.

Picking our way through the debris of a very large wet slab avalanche that occurred on 4/27 on Sunburst. These things are nothing to mess with! 04.29.2022

 

Weather
Sat, April 30th, 2022

Yesterday: Skies were partly cloudy, with increasing cloud cover in the afternoon. High temperatures were in the upper 20’s to mid 40’s F, with overnight lows in the low 20’s to mid 30’s F. Winds were blowing 10-20 mph out of the east with gusts to 45 mph. no precipitation was recorded.

Today: Active weather is returning, with light rain showers this morning in Girdwood. We are looking to get around 0.2-0.8″ precipitation in Girdwood and Turnagain Pass, which will fall mostly as rain below 1500′, and should bring 2-5″ snow above that. Portage and Placer could receive closer to 0.8″ precipitation equalling 6-8″ snow at higher elevations. Winds are expected at 20-40 mph out of the east with gusts of 35-50 mph.

Tomorrow: The storm will intensify tonight, bringing over an inch of water to Girdwood and Turnagain Pass by midday tomorrow, and 2-3″ water to Portage and Placer by the end of the day. Strong easterly winds are expected to continue into tomorrow morning before starting to back down, with sustained speeds of 25-30 mph and gusts of 30-50 mph. The rain level is expected to move up to 1800-2000′, with high temperatures in the mid 30’s to low 40’s F and overnight lows back down in the mid 20’s to low 30’s F

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 39 0 0 95
Summit Lake (1400′) 37 0 0 26
Alyeska Mid (1700′) 38 0 0 N/A

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 24 ENE 12 46
Seattle Ridge (2400′) 29 SSE 12 29
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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.
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