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Avalanche Advisory

Turnagain Area Avalanche Advisory
Sunday, March 31st 2019 7:00 am by Wendy Wagner
ARCHIVED ADVISORY - All advisories expire after 24 hours from the posting date/time.
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The Bottom Line

VERY WARM temperatures will increase the avalanche danger from LOW this morning to CONSIDERABLE by this afternoon/evening. Large and dangerous wet loose, wet slab and glide avalanches may release naturally once the sun softens surface crusts and weakens the snowpack. All slopes above 1,000' facing East, South and West that see direct sunshine should be carefully evaluated before traveling. Watch and avoid being under glide cracks! Cornices are breaking off in the heat of the day - give them an extra wide berth. 

PORTAGE VALLEY:  Summer trails with avalanche terrain overhead, such as Byron Glacier Trail and Crow Pass, are not recommended in the afternoon or evening due to the possibility of an avalanche occurring above. 

SUMMIT LAKE (& INTERIOR EASTERN KENAI MTS):  Human triggered slab avalanches remain possible in upper elevation terrain on all aspects. This area has a thin snowpack with many weak layers. High elevation sun-affected slopes are the most suspect for triggering a slab. 

SEWARD/LOST LAKE:  The snowpack is warming up and dangerous avalanche conditions are occurring late in the day in this area as well. A large avalanche released on Mt. Marathon Thursday


 Show the Complete North American Avalanche Danger Scale
3 Considerable Alpine / Above 2,500' Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision-making essential.
3 Considerable Treeline / 1,000'-2,500' Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision-making essential.
2 Moderate Below Treeline / Below 1,000' Travel Advice: Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
Special Announcement
  • Warm conditions and large avalanches are occurring at Hatcher Pass as well. Be sure to check out HPAC's Sunday's forecast!! 

Avalanche Problem 1

Wet Loose

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
Small

Size

Although the days have been warm lately, today will be hot! As of 6am this morning air temperature along ridgelines are several degrees warmer than previous mornings and sit in the 30'sF. Direct sunshine and light winds could push afternoon temperatures into the 40'sF and even 50F in the mid and upper elevations. The snowpack has already seen many days of a springtime melt-freeze pattern, yet today our hackles should be up for unusual avalanches in the afternoon and evening. Not only are the mid-elevations expected to see wet avalanches, we could see wet avalanche activity on sunny slopes in the high alpine. Wet loose avalanches will be the most likely, but wet/moist slabs are possible.  

Yesterday we know of two new avalanches. One was a glide/full depth avalanche at 5:30pm on Seattle Ridge's Repeat Offender slide path. This piled 8-10 feet of debris on to the common motorized up-track. See the photos and video below. The other was a glide on Lipps SW face that reported to have released around 11:30am.

Things we can do for a safe day in the mountains is plan ahead. Know the terrain you are traveling and if it will be affected by the sun. The boot test is a great way to assess how the daytime warming is, or is not, affecting the surface. If your boot easily sinks into mushy wet snow, it's time to get onto shaded slopes or off the one you are on and well away from any runouts. Wet loose avalanches can start small from a person pushing soft wet snow as they ski or ride. If the terrain is large enough, this small slide can turn into a large and unmanageable avalanche. Wet avalanches can send debris far and to places we may not expect.

CORNICES: Cornices are very large and direct sunshine will destabilize them. A cornice fall has the potential to trigger an avalanche on the slope below and could break farther back than expected. 

 

 

Glide/full depth avalanche just above the common motorized up-track on the Repeat Offender slide path. Debris covered the up-track with 8-10' of debris. 

Looking at avalanche and debris from the up-track.

 

Cornices are peeling off and a significant danger to people getting pulled off a ridge. Getting washed over by cornice triggered avalanche from below is also a hazard.

 


Avalanche Problem 2

Glide Avalanches

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
Small

Size

Glide cracks are popping and avalanching daily. If any time is good to simply avoid traveling under glide cracks, now is the time. A large crack was reported to have released on Lipps SW face yesterday and the Seattle Ridge full depth avalanche is likely a glide that did not have a crack present before releasing; making our current avalanche situation more unpredictable. Remember, glides can release even if a hard surface crust is present (unlike the wet loose and wet slab avalanche problems). Many cracks are opening up in popular terrain and keep an eye out for them. 

With so many old glide avalanches scarring the mountainsides, how do we know if any are new? This is good information as new glide releases tell us they are 'active' and more can be expected.  


Additional Concern

Deep Persistent Slabs

South of Turnagain in Summit Lake and areas in the interior Kenai Peninsula have a very poor snow structure with variety of old weak layers in the mid pack (facets and buried surface hoar.) Triggering a persistent slab 2-3’ deep as slopes warm in the afternoon sun is possible at the upper elevations. The avalanche seen on Butch Mtn. in Summit Lake last week is a good reminder that sunny hot days can surprise us! Keep in mind deeper weak layers could be lurking in these areas and sunlit slopes are the most suspect.


Mountain Weather

Yesterday:  Sunny skies with light ridgetop winds were over the region. Temperatures reached 40F at 2,500' and 32F at 4,000'. Overnight a warmer air mass has moved in maintaining these warm upper elevation temperatures. Valley bottoms have cooled slightly and sit in the upper 20'sF. 

Today:  Very WARM air with sunny skies are forecast. Ridgetop winds should be light and variable. Temperatures may reach 50F at 2,500' with direct sunshine and up to 40F at 4,000'. 

Tomorrow:  Sunny skies will prevail as the ridge of high pressure over us remains entrenched. Temperatures tomorrow look to remain warm, yet slightly cooler air may stream in for Tues/Wed. Clouds and a chance for precip is still on the horizon for Thur/Fri, but models are trending at keeping this to our South and we may see sunny skies for the work week.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 38   0  68
Summit Lake (1400') 37  0 61 
Alyeska Mid (1700') 37  22 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 29   variable 19 
Seattle Ridge(2400') 35  variable 

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
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