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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Sat, April 18th, 2020 - 7:00AM
Expires
Sun, April 19th, 2020 - 7:00AM
Forecaster
CNFAIC Staff
Conditions Summary

Saturday, Apr 18th UPDATE:

DANGEROUS AVALANCHE CONDITIONS continue in the backcountry today and through the weekend. Travel in avalanche terrain is NOT recommended, avalanches can run into valley bottoms and be very large and dangerous.

Yesterday was another very active avalanche day. The snowpack continued to ‘fall apart’ with multiple large to very large wet loose, wet slab and glide avalanches observed in Girdwood, Portage, Turnagain Pass, Summit Lake and south to Seward. These were large wet avalanches releasing due the snowpack warming dramatically. Many of these ran to the ground taking out the entire season’s snowpack. Today temperatures remain above freezing and skies will be partly sunny. Rain is in the forecast tomorrow into next week. Expect avalanche activity to continue during this shed cycle.

This is not a time to be on hiking trails or in the backcountry unless you know for certain you are well away and far out from under avalanche paths. Roofs with remaining snow/ice are also likely to shed – heads up!

This is the final conditions update. The CNFAIC is wrapping up operations for the season. We would like to thank everyone for their support during the past two weeks of suspended forecasts. Look for our Annual Report on April 25th. Although the forecasts have finished, the avalanche season has not  – please see below for some SPRINGTIME AVALANCHE TIPS.  

  • Current conditions? Keep tabs on our Observation Page.  We will be posting all observations/reports sent in to us.
  • “Like”  the Friends of the Chugach National Forest Avalanche Information Center on Facebook and follow us @chugachavy on Instagram. We will continue to post throughout the summer.
  • As always, check the nearby weather stations before heading out.  You can find these on our  Weather Page.

We would like to extend a huge  THANK YOU  to all the folks who have taken the time to send in observations over the season. Your reports are integral in providing the highest quality information.

Additionally, THANK YOU to all of you who have supported the CNFAIC through donations, memberships and a variety of other means.  This is the foundation we continue to build upon – we would not be here without you!

We would also like to thank our non-profit arm, the Friends of the CNFAIC.  Half of our operating budget comes directly from you through the ‘Friends’ organization.  This amazing and selfless group has a tireless passion for keeping us safe in the backcountry.  Their fundraising efforts allow the Avalanche Center to be a reality – literally. And of course, we would not be here without the support of the Forest Service and the wonderful Glacier Ranger District.

Last but far from least, we would like to thank our professional partners for sharing their insights, information and wisdom, which greatly improve our forecasts:

  • Alaska DOT Avalanche Program
  • Alyeska Snow Safety
  • Chugach Powder Guides
  • Chugach Electric Avalanche Program
  • Alaska Railroad Avalanche Program
  • Alaska Guide Collective
  • Alaska Avalanche School
  • Alaska Pacific University’s Snow Science Program
Thanks to our sponsors!
Sat, April 18th, 2020
Recent Avalanches

Two examples of the many large avalanches observed yesterday. Most of the images throughout the Springtime Tips are from the avalanche cycle over the past two days.

Wet slabs on the east side of Pyramid Peak. 4.17.20 

Wet loose avalanches in Summit Lake. 4.17.20

Avalanche Problem 1
  • Spring Conditions
    Spring Conditions
Spring Conditions
Warmth has a tricky effect on snow. On the one hand it speeds up the stabilization of the snowpack (reduces the chance of slab avalanches). But a SUDDEN rise of temperature increases the chance of slab avalanches considerably. When this warm period is followed by cooling down, then the chance of slab avalanches reduces. Even more so: the more often the temperature changes, the more stable the snowpack becomes when looking at slab avalanches. Once the temperature becomes too warm we have to deal with wet snow avalanches.
More info at Avalanche.org

SPRINGTIME AVALANCHE TIPS –  Timing is everything! The spring transition can have an unexpected effect on snowpack characteristics. Stable snow can become weak and hazardous in a matter of hours. What to look for? Ask yourself these questions: Am I dealing with winter snow (cold and dry) or spring/summer snow (wet, warm and/or crusty and refrozen)? Or is it some combination? What weather factors have affected the snowpack today and recently?

Remember the Red Flags that indicate instability!

  • Are there recent avalanches? What kind?
  • Cracking in the snow? Collapsing?
  • New snow? Rain? What elevation?
  • Wind loading? How strong for how long?
  • Rapid warming? Did it freeze last night? How many nights with no freeze? How deep are you sinking into mushy wet snow?

On any given day conditions can range from warm and sunny T-shirt weather, to pouring rain, to cold and snowy mid-winter conditions. Being able to recognize and respond to specific avalanche concerns is key in making effective decisions in avalanche terrain. 

Hiking on summer trails during the springtime warm-up (including the Byron Glacier trail, Crow Pass, Devil’s Pass, Russian Lakes trail and Crescent Creek trail) can be very dangerous.  Extra caution is advised for trails that cross under avalanche paths. Avoid being under large snow covered slopes this spring as avalanche hazard does remain. Most common times for natural springtime avalanches are during sunny afternoons/evenings or periods of warm rainy weather. Know that an avalanche occurring above you could send debris to snow-free zones and valley floors.

Make sure you consider avalanche danger before using hiking trails.

Loose Snow Avalanches: Both dry and wet loose avalanches are common springtime avalanche concerns. Pay close attention in steep terrain, especially when the sun first hits freshly fallen snow. Remember loose avalanches can be particularly hazardous if they push you into a terrain trap. Wet loose avalanches can trigger wet slabs on the slopes below.

Wet loose avalanches on Butch in Summit Lake 4.17.20.

Wet Slab Avalanches: Wet slab avalanches are a combination of a slab, a weak layer or interface and water percolating down to the weak layer or interface. Often times there is a crust involved as the bed surface or some harder layer that the water lubricates.  As temperatures rise and/or rain falls at upper elevations these could happen even on the Northerly slopes. These tend to be large and destructive when water is first being rapidly introduced to a somewhat drier snowpack.

Wet slab triggered by a wet loose avalanche, Boston Bar above Six Mile Creek. 4.17.20

Dry Slab Avalanches: It is still possible to get significant snowfall this time of year. If it is raining hard at lower elevations depending on the temperature it may being snowing hard up high. Pay attention to how much new snow has fallen and what surface it is sitting on. Is there a foot of new snow sitting on surface hoar or facets or a hard crust or over wet snow? Even without a persistent weak layer between the slab and the bed surface, it is still possible to trigger dangerous slab avalanches. These slabs may also be tender and reactive right as they start to warm in the spring sun or with a rapid temperature rise. 

Storm slab triggered on Wolverine. 4.10.20. Photo: Mike Records. This occurred prior to the recent warm up. 

Wind Slabs: It is also important to continue to pay attention to wind direction and loading patterns. New snow or older dry loose snow can quickly be loaded on leeward slopes and form touchy wind slabs. Look for areas of pillowed snow and watch for cracking. Again, you may be seeing a rain storm and forget that it is actually snowing and blowing up high. Check the weather page! What direction has the wind been blowing from? How strong for how long?

Cornices: Some slopes still have large cornices looming above them.  Knowing exactly what will tip the scales is difficult. Some factors that contribute to cornice fall are direct sun, heat from rising temperatures, and new snow with wind.  Give cornices a wide berth and take measures to minimize your exposure beneath them. Remember they have a tendency to break much further back than expected.

Cornices and wet loose activity in Warm-up Bowl. 4.17.20

Glide Avalanches: Glide cracks are appearing and we have had releases this week. Remember glide avalanches are very unpredictable, not triggered by humans and that they are the entire snowpack sliding to the ground. Avoid travel under glide cracks.

Glide avalanches and wet loose avalanches on Wolverine and Shark’s Fin. 4.17.20

Below are some ways to both anticipate and deal with the above mentioned avalanche concerns:

  • Watch for the “shed cycle or complete melt-down” on the higher elevation slopes still holding snow. This happens when the dry snowpack transitions to wet. The snowpack becomes mushy, saturated and unsupportable. Wet avalanches often begin to release near the ground as; wet slabs, wet loose avalanches and glide avalanches. Anticipate this by keeping an eye on the ridgetop weather stations (click HERE). Avalanche activity often follows 3 or 4 consecutive nights of no re-freeze at the higher elevations. Rain can accelerate the avalanche cycle. Careful route planning to stay out from under slopes with wet and rotten snow is essential during this period.

‘Shed cycle’ is beginning, large wet loose avalanche on Seattle Ridge. 4.17.20

Very large wet slab avalanche in Crow Creek. 4.16.20

  • Sinking into wet and rotten snow on skis or a snowmachine or over your boot tops is a sign that it’s time to exit the area. Following the aspects as the sun heats up the slopes over the course of the day, East to South then West, can make for great riding/skiing days, ending in sunny tailgating! High elevation North slopes may still have winter like conditions but may also become wet if the temperatures rise enough.
  • Keep in mind, cloud cover ‘holds in the heat’ and can dramatically limit overnight refreezing. A shallow to no refreeze will not only give daytime heating a jump start on weakening the pack, but can produce less than stellar riding conditions.
  • Beware of warm storms where rain is falling on snow, especially when rain is falling on cold dry snow. This can quickly increase the avalanche danger.
  • Stay off of CORNICES.  When approaching from the side or above, make sure you can see where the cornice ends and the underlying terrain begins. If you can’t see that transition area, move away from the edge. If you find you and your group below cornices, expose only one person at a time and move efficiently through those areas.
  • As always wear avalanche rescue gear and practice safe travel protocols!
  • Lastly, don’t forget to plan your route back to the car. Does it take you under slopes that were frozen and safe earlier in the day, but now have been cooking in the sun waiting to slide on your return? Under cornices?

How deep are you sinking into the snowpack? Pay close attention to overnight freezing, rising temperatures and changing surface conditions!

Until next season, be safe, stay healthy, and have a great summer! –Wendy, Aleph, Ryan and Graham

Additional Concern
Spring Conditions
Warmth has a tricky effect on snow. On the one hand it speeds up the stabilization of the snowpack (reduces the chance of slab avalanches). But a SUDDEN rise of temperature increases the chance of slab avalanches considerably. When this warm period is followed by cooling down, then the chance of slab avalanches reduces. Even more so: the more often the temperature changes, the more stable the snowpack becomes when looking at slab avalanches. Once the temperature becomes too warm we have to deal with wet snow avalanches.
More info at Avalanche.org

When you are done recreating for the winter season remember to take care of your avalanche gear!

  • Take the batteries out of your beacon and store it in a dry place.
  • Make sure your shovel and probe are dry when you put them away.
  • Unhook your air bag canisters. If you have a JetForce pack it is recommended that those are stored with the battery at half charge in ‘storage mode’.

Weather
Sat, April 18th, 2020

For the most up to date weather please see our weather page!

Observations
Recent Observations for Turnagain Pass
Date Region Location
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03/24/20 Turnagain Observation: Turnagain – Road Observations
Riding Areas
Updated Mon, October 26th, 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
Closed
Placer River
Closed
Skookum Drainage
Closed
Turnagain Pass
Closed
Twentymile
Closed
Seward District
Carter Lake
Closed
Lost Lake Trail
Closed
Primrose Trail
Closed
Resurrection Pass Trail
Closed
Snug Harbor
Closed
South Fork Snow River Corridor
Closed
Summit Lake
Closed

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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.