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Avalanche Advisory

Turnagain Area Avalanche Advisory
Thursday, March 21st 2019 7:00 am by Heather Thamm
ARCHIVED ADVISORY - All advisories expire after 24 hours from the posting date/time.
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The Bottom Line

The avalanche danger will remain HIGH today for Turnagain Pass, Girdwood and Portage due to above freezing temperatures and the likelihood of natural wet slab avalanches below 3000’. In the alpine natural and human triggered storm slab 2-3’ deep are 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: Travel in runout zones from avalanches including venturing along and past the Byron Glacier Trail continues to be not recommended. Very large avalanches have been observed in Portage over the past few days and are expected to continue today.

SUMMIT LAKE (& INTERIOR EASTERN KENAI MTS): Extra caution is advised. Large human triggered avalanches remain likely. Avalanches have the potential to release in old buried weak layers.

SEWARD/LOST LAKE: Warm temperatures, strong winds and a mix of rain and new snow have added more stress to the snowpack. Although less precipitation fell yesterday, triggering a large and dangerous avalanche is likely.


 Show the Complete North American Avalanche Danger Scale
4 High Alpine / Above 2,500' Travel Advice: Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
4 High Treeline / 1,000'-2,500' Travel Advice: Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
4 High Below Treeline / Below 1,000' Travel Advice: Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
Special Announcement

20 years ago today, March 21, 1999 a massive avalanche took the lives of 6 snowmachiners on Seattle Ridge in Turnagain Pass. Our deepest condolences are with the family and friends of those lost that day. In commemoration, CNFAIC forecasters and Friends of CNFAIC, will be at the Turnagain Pass motorized lot on Saturday, March 23rd, from 12pm - 2pm. We welcome any and all to stop by for a hot dog, say hi, chat about the current avalanche conditions, and test your avalanche rescue gear. We'll have a few beacons buried so you can practice your skills. 

Our thoughts are also with the family and friends of the skier killed in an avalanche on March 9th, 2019 near the Crescent Saddle Cabin. The detailed report can be found on our accidents page HERE. A big thank you to the backcountry partners involved in this accident for their willingness to share what happened so we can all learn. 

Heading to Hatcher Pass? Be sure to check out the Hatcher Pass Avalanche Center mid-week snow and avalanche summary HERE. 


Avalanche Problem 1

Wet Slab

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
Small

Size

Over the last two weeks we’ve seen some big storms and some impressive avalanche activity. Yesterday was similar, except it arrived with very warm temperatures and heavy rain to ridgetops. In Turnagain Pass .9” of rain was recorded and in Girdwood (Alyeska midway) 2.74” of rain was recorded. This is a lot of water in short period of time, especially in Girdwood and the Northern side of Turnagain Pass. We estimate rain/snow line fluctuated between ~3000’and ~2500’. Ridge top winds were in the 40-60’s mph with a gust to 101mph on Sunburst. Numerous natural wet slabs were observed on Seattle Ridge by the afternoon and Portage Valley reached 50F. Temperatures have remained above freezing overnight at Seattle Ridge weather station (2400’) and overcast skies are keeping the snowpack insulated. This means the snow is still wet and saturated in the mid and lower elevations. Wet slab avalanches are not something to mess with. These are unpredictable and unsurvivable if someone was to get caught. Until temperatures drop below freezing and the snowpack has a chance to drain, we recommend avoiding avalanche terrain. To compound this situation another storm is expected to arrive late afternoon with another round of heavy rain and strong winds overnight.


Storm Slabs:
In the alpine, where 1-3’ of snow fell yesterday, storm slabs are expected to be unstable. Strong Easterly winds 25-40mph will continue throughout the day and will be adding stress to the upper elevation snow pack. Natural and human triggered storms slabs 2-3' are likely where the snow is dry.

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. Not as much precipitation fell overnight, but temperatures remain very warm. Winds and warm temperatures will be adding stress to the snowpack today and triggering a dangerous slab avalanche 1-3’ thick remains likely in the alpine. Triggering a wet avalanche is likely below treeline. 

Natural wet slab avalanches on Seattle Ridge near the motorized lot yesterday afternoon. 

 

Natural wet slab avalanche entraining snow to the ground on Seattle Ridge, SE aspect, near Bertha Creek. 


Additional Concern

Glide Avalanches

Several glide cracks have released in the last few days including one on Seattle Ridge yesterday. In Girdwood two were observed yesterday on Raggedtop and Penguin Ridge. Similar to wet slab avalanches these are very unpredictable and impossible to manage.

Glide avalanche on Seattle Ridge released yesterday, just North of the uptrack. 


Mountain Weather

Yesterday: Temperatures increased into the 40Fs at sea level and mid 30Fs at ridgetops. Portage Valley hit 50F yesterday morning. Heavy rain fell below 3000’ most of the day. Turnagain pass recorded .9” of rain. Alyeska midway recorded 2.76” or rain and Bear Valley in Portage recorded 2.02” of rain. Ridgetop winds were Easterly, 40-60 mph with gusts in the 70-80s. Overnight temperatures remained above freezing at 2400’ at Seattle Ridge weather Station with obscured skies.

Today: Rain will continue throughout the day and become heavy rain by this evening as another storm tracks through our region. Today 0.3” rain is expected with 1” of rain overnight. Temperature will remain in the 40Fs at sea level, mid 30Fs in the mid elevations. Rain/snow may drop a little by this evening to ~2000’. Strong Easterly ridgetop winds 30-40mph will continue today bumping into the 50-60’s by this evening.

Tomorrow: Skies will remain obscured, and rain is expected to continue through the day. Above freezing temperatures will continue in the lower and mid elevations. Strong winds will start to diminish by Saturday morning.

*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')  39  rain 0.9  78 
Summit Lake (1400')  41 rain  0.4   28
Alyeska Mid (1700')  37 rain   2.74 73 

 

RIDGETOP 24-hour data (6am - 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 31  ENE  41  101 
Seattle Ridge(2400') 35  *SE  *20  *50 

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).

Winter snowmachine use open/closed status and riding conditions updates

Riding status is not associated with avalanche danger. An area will be open to motorized use in accordance to the Forest Management Plan when snow coverage is adequate to protect underlying vegetation. Backcountry hazards including avalanche hazard are always present regardless of the open status of motorized use areas.

(Updated: May 06, 2019 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: ClosedClosed as of 4.3.19
Placer River: ClosedClosed as of 3.20.19 due to lack of snow.
Skookum Drainage: ClosedPlacer access closed as of 3.20.19 due to lack of snow.
Turnagain Pass: ClosedClosed as of 5/6. Thanks for a great season all, see you next winter!
Twentymile: ClosedClosed as of 3.20.19 due to lack of snow.
Seward District
Carter Lake: Closed
Lost Lake Trail: ClosedClosed as of 3.22.19 due to lack of snow
Primrose Trail: ClosedClosed as of 4.3.19 due to lack of snow
Resurrection Pass Trail: ClosedClosed for the 2018/19 season. Next season will be open to motorized use.
Snug Harbor: ClosedClose as of 5.1.2019
South Fork Snow River Corridor: ClosedClosed as of 3.20.19 due to lack of snow.
Summit Lake: Closed

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The information in this advisory is from the U.S. Forest Service, which is solely responsible for its content. This advisory describes general avalanche conditions and local variations always occur. This advisory provided by the Chugach National Forest, in partnership with Friends of the Chugach National Forest Avalanche Information Center.


USFS SNOW AND AVALANCHE HOTLINE (907) 754-2369
If you have comments or questions regarding CNFAIC operations or winter recreation management, please email staff@chugachavalanche.org
© 2019 Chugach National Forest Avalanche Information Center. All rights reserved.
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