Avalanche Advisory

Turnagain Area Avalanche Advisory
Monday, December 11th 2017 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

The avalanche danger is HIGH due to heavy rain, wet snowfall and strong wind. A very potent warm and wet storm has brought rain near the top of treeline and possibly higher. This has triggered a natural wet avalanche cycle in the Treeline elevation band and up to 2,700'. Above this, natural storm snow avalanches are likely occurring in the Alpine. Today, natural avalanches will remain likely and human triggered avalanches very likelyTravel in avalanche terrain is NOT recommended

Below 1,000' there is a CONSIDERABLE avalanche danger for debris running into these lower elevations from avalanches releasing above.

 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

Elevated avalanche danger remains throughout Southcentral, AK due to continued stormy weather. If you are headed to Hatcher Pass check out and for Valdez,  Also, there have been reports of unstable snow and human/natural triggered avalanches near Petersville and the Dutch Hills area.

Avalanche Problem 1

Rain falling on snow has initiated a widespread avalanche cycle in the mid elevation band. The Girdwood Valley saw 2.4" of rain in the past 24 hours below ~2,200' and subsequently significant wet slab and wet loose avalanche activity. Wet avalanches were reported up to 2,700' in elevation, which is just above the rain/snow line and where very wet snow is falling. This trend is expected to continue today. There is not much known about the activity yet at Turnagain Pass where around 2" of rain fell or at Summit Lake with 1" of rain, but we can expect wet avalanche activity in these areas as well. The rain/snow line has been fluctuating between 2,200' and 2,500' in general. Yes, this is soaking the meager snowpack between 1,000' and 2,500' and allowing the alders to bounce back up. 

Image: A look at Tincan Ridge at Turnagain Pass being wetted down up to the top of the trees. Once these storm cycles cease, the upper elevations should look much different, the lower will hopefully remain snow covered!

Avalanche Problem 2

In the Alpine, wet and heavy snow is falling, which becomes drier with elevation. From our rainfall totals at the snow stations, we can expect that during the past 24 hours 1-2+' of snow has accumulated. Cornices are building and the weak pre-existing snowpack continues to be loaded. Storm snow avalanches that include storm slabs, wind slabs and cornice breaks all can be expected today at the high elevations. What can also be expected is the snow may stick fairly well and instead of avalanche immediately as a storm snow problem, it may overload and tip the balance of the weak snow sitting near the ground and create a very large avalanche, taking most of the snowpack with it. 

Again, the message is simple for today, avoid avalanche terrain. This means steering clear of slopes 30 degrees and steeper with nothing steeper above or near you. Also, be extra cautious of evaluating runout zones.

Mountain Weather

Heavy rain and overcast skies filled the region yesterday. Rain/snow line looks to have been between 2,200' and 2,500' depending on location. Around 2-2.5" of rain fell while 1-2+ feet of heavy wet snow fell at the upper elevations. Much less precipitation fell inland on the Kenai (Summit Lake area). Winds have been strong from the East, averaging 20's-30's mph with gusts in the 70's. Temperatures are way too warm - low to mid 40's at sea level and up to 32F along the 3,000' ridgelines.

For today, Monday, we can expect this very warm system to move out and precipitation rates diminish. Around .3" of rain is expected today below 2,900' and 1-3" of heavy snow above. Temperatures should remain very warm, in the mid 40's at sea level and 32F along the ridgelines. Winds from East and Southeast will remain moderate to strong, in the 20's - 30's mph with much stronger gusts. Slightly cooler temperatures are expected tonight along with .5-.6" of rain below 2,100' and 3-6" of snow above as another system moves in.

For Tuesday and heading into the week, the active warm and stormy weather pattern with continue with the next storm moving in tonight. However, "by the end of the work week there is high confidence for the anticipated pattern change" says the NWS, meaning a return to cooler temperatures and a break from the incessant stormy weather.

*Center Ridge and Summit Lake SNOTEL stations stopped reporting at 9pm and 11pm respectively. Values below are estimates.
**Reported 24-hour water at the RWIS station at Turnagain Pass (1000' elev.) and RWIS Summit Lake (1300' elev.)

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') *35  0 (rain)   **1.9  *25
Summit Lake (1400') *35  0 (rain)   **1 *10 
Alyeska Mid (1700') 35  0 (rain)  2.4  15 


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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 28  ENE  36  77 
Seattle Ridge(2400') 31  SE  28  65 

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 )

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.

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