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Avalanche Advisory

Turnagain Area Avalanche Advisory
Thursday, December 7th 2017 5:14 am by Wendy Wagner
ARCHIVED ADVISORY - All advisories expire after 24 hours from the posting date/time.
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The Bottom Line

Avalanche danger is expected to increase to HIGH by this afternoon as another round of rain, snow and wind moves in. Around 10-15" of snow falling today in the Alpine and 1" of rain below 1,500' will continue to overload a very unstable snowpack. Natural avalanches are expected and human triggered avalanches will be very likely. As this stormy weather persists, travel in avalanche terrain is NOT recommended. This means avoiding slopes 30 degrees and steeper, including runout zones.

Below 1,000' there is a CONSIDERABLE danger where debris running into these lower elevations from avalanches above 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.
3 Considerable Below Treeline / Below 1,000' Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision-making essential.
Special Announcement

 **Increased avalanche conditions have been seen across Southcentral, Alaska**

This Valdez Avalanche Center has issued extreme avalanche danger, the Richardson Highway was closed yesterday due to an avalanche over the road . Also, dangerous avalanche conditions have been seen at Hatcher Pass, recent observations and forecast at hpavalanche.org

Motorized use on Turnagain Pass remains closed due to insufficient snow cover.  Please see riding area status at the bottom of this page for the most up-to-date information.

Join us this SATURDAY in Seward:
Know Before You Go - Avalanche Awareness at the Seward Community Library, December 8th, 1 pm - 4 pm | FREE Join CNFAIC for a great intro to avalanche recognition and rescue, including hands-on beacon practice.


Avalanche Problem 1

Temperatures are climbing today ahead of another round of precipitation. In the upper elevations above treeline, we are looking at 10-15" of moist snow to fall with another 5-8" tonight. Below 1,500' up to an inch of rain is expected today with another .5" tonight. The rain/snow line should creep up higher that we have seen with this storm cycle - up to and possibly over 1,500'. The forecast snow amounts are not exceptional for a HIGH danger day, but what is exceptional is the very unstable nature of our existing snowpack.

There is a very reactive layer of facets sitting under the storm snow from the past week, which is anywhere between 18 and 36" below the surface. By tonight we should have another foot or so of new snow to add to this slab, making it anywhere from 2-4' in thickness. In the event these snow amounts verify, avalanches occurring today could be larger than we have seen so far and send debris into valley bottoms. Additionally, they have the potential to propagate very wide and around terrain features on multiple aspects. Warmer temperatures will also add stress to the snowpack and enhance likelihood of triggering. 

Just how reactive are these facets? On Tincan, two avalanches were remotely triggered by a group of people yesterday from hundreds of feet away and on different sides of the ridge. What happened was a group skied/rode down Tincan's Common Bowl (photos below) and re-grouped up on a bump below. While the group was on this 'bump' it appears they triggered a collapse and very large 'whumpf' that was heard from others in the area. Subsequently, an avalanche released ~600' away. And, this is the even more impressive part, the collapse traveled over the ridge and released another avalanche on the North side. 

Photo of tracks in Tincan's Common Bowl. Party skied one at a time, grouped up below on knoll, triggered a collapse from knoll that propagated hundreds of feet triggering two separate avalacnhes on different aspects. (Photo: Brad Cosgrove)


Photo of avalanche that released on the North side of Tincan a thousand feet away or more from the group who triggered the collapse.


Close up on the avalanche on the Southwest aspect and under the CFR ridge. (photo: Gabe Gibbs)

 

Once again, with a snowpack as precarious as this, this is not the time to be traveling into avalanche terrain. As the snow piles up on top of the facets, the avalanches are becoming larger. They are also likely to become a bit more stubborn to trigger, which makes for a very scary snowpack and hard to manage avalanche problem. Very conservative choices are needed for safe days in the backcounty right now. Sticking to slopes under 30 degrees with nothing steeper above you, or next to you, is key. 

 

Snowpack on Sunburst. The current problem, facets below the slab clearly seen. 

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Avalanche Problem 2

Winds from the East have begun to increase this morning and are expected to blow 25-45mph with gusts into the 60's or more through tonight. This will continue to load leeward slopes and cross load snow into gullies. Cornices will also continue to build along ridgelines. Naturally or human triggered wind slab avalanches or cornice falls are likely, but what is more of a concern is the potential for one of these to trigger a much larger and dangerous persistent slab avalanche as discussed above. 


Mountain Weather

Yesterday was a break between storms. Skies were mostly sunny and winds were light and Easterly around 5mph. Temperatures dropped slightly at sea level to the upper 20's and at the upper elevations to the low 20's F. Overnight, clouds and warmer air has streamed in allowing temperatures to rise a few degrees (low 30's F sea level and upper 20's along the ridgelines). Winds have increased overnight from the East and are blowing 25-35mph with gusts up to 50mph. 

Today, we can expect winds to continue increasing to 35-45mph with gusts over 60mph from predominantly the East. Temperatures will continue climbing to ~38F at 1,000' and 30-32F along the ridgelines. An inch of rain is forecast by 6pm tonight below 1,500' and 10-15" of snow above 1,500'. Another .5" of rain is expected tonight along with 5-8" of snow in the Alpine.

Tomorrow, this 'pulse' of moisture looks to shift East giving us a slight break in precipitation intensity before the fire-hose of moisture points more in our direction late Saturday. In general, this active pattern of warm, windy and wet weather is expected to continue into next week. 
 

*Center Ridge SNOTEL is reporting erroneous temperature data. See Turnagain Pass DOT weather station for accurate temperature at 1000'.

**Seattle Ridge anemometer is rimed.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') *28  30 
Summit Lake (1400') 23  11 
Alyeska Mid (1700') 29  0.05  21 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 24  ENE  17  50 
Seattle Ridge(2400') 26  n/a**   n/a**   n/a**  

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, 2018 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: ClosedClosed as of April 20th
Placer River: ClosedClosed as of April 17th
Skookum Drainage: ClosedClosed as of April 1st.
Turnagain Pass: ClosedClosed as of May 7th. Happy summer, see ya when the snow flies!
Twentymile: ClosedClosed as of April 13th
Seward District
Carter Lake: ClosedClosed as of 4/27
Lost Lake Trail: ClosedClosed as of April 13th
Primrose Trail: ClosedClosed as of April 13th
Resurrection Pass Trail: ClosedClosed as of April 20th
Snug Harbor: ClosedClosed as of 4/27
South Fork Snow River Corridor: ClosedClosed as of April 13th
Summit Lake: ClosedClosed as of April 20th

Subscribe to the Turnagain Area Avalanche Advisory:

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
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