Avalanche Advisory

Turnagain Area Avalanche Advisory
Thursday, April 16th 2015 7:00 am by Graham Predeger
ARCHIVED ADVISORY - All advisories expire after 24 hours from the posting date/time.
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The Bottom Line

MODERATE avalanche danger exists in the alpine and at treeline elevations today where storm slabs less than 48 hours old are quickly settling out.  Human triggered avalanches in the 1-2’ range, comprised of storm snow will be possible as the snowpack continues to adjust to Tuesday’s (19” in 19hrs) storm plus any new snow added today.  Additional avalanche concerns today will come in the form of loose or wet loose avalanches initiated by warm ambient temperatures. 

A much smaller possibility exists for large avalanches to be triggered deep in the snowpack where we know that weak snow and interfaces exist.  These are unlikely to be affected by a skier but serve as a good reminder to constantly practice safe travel protocol in the mountains.

 Show the Complete North American Avalanche Danger Scale
2 Moderate Alpine / Above 2,500' Travel Advice: Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
2 Moderate Treeline / 1,000'-2,500' Travel Advice: Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
0 NO RATING Below Treeline / Below 1,000'
Special Announcement

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We are currently issuing advisories 5 days a week until our final advisory on Thursday, April 30th.  Advisories will be posted at 7 am each day except Mondays and Wednesdays.

Avalanche Problem 1

Tuesday provided a heavy dose of localized (to Turnagain pass) storm snow in the core advisory area with up to 19” accumulating at the Center Ridge SNOTEL site (1880’) in 19 hours.  The storm quickly shut off with only a trace of snow falling yesterday allowing Tuesday’s storm slab to settle to about 12”.  This load coupled with 3-5” forecasted today is enough of a concern to warrant careful snowpack and terrain evaluation before skinning up or jumping into committing terrain.

Storm slabs/ wind slabs:

These are expected to be as deep as 1-2’ in areas affected by the wind, proving large enough to bury a person.  We don’t have a lot of information in terms of how well this recent storm is bonding to, or affecting underlying weaknesses so it’ll be prudent to pay attention to any red flags including recent avalanches, shooting cracks or whumphing prior to committing to steep terrain.  If experiencing and red flags today, these are the sure signs that the snowpack below your skis is unstable and slope angles need to be dialed back.  Quick hand pits or jumping on small (no consequence) test slopes will be a good way to gather more data while making your own snowpack assessment.

Deep slab/ persistent weak layers

This is less of a concern today but is still being pondered, particularly on the South end of the advisory area where persistent weak layers may be found closer to the surface.

With the majority of the ski season behind us, now is not the time for complacency.  Continue to practice safe travel protocols.  Ski slopes one at a time and utilize lookouts, positive communication, escape routes and islands of safety. 

Avalanche Problem 2

Natural and human triggered sluffs are expected in the new snow on all aspects and elevations. Though the Sun isn’t forecasted to make an appearance today, warm ambient temperatures and potentially rain at lower elevations may be enough to trigger loose snow sluffing and roller balls above and below treeline. 

Mountain Weather

Yesterday’s weather can be described as Grey-bird and warm with light winds from the east.  Temperatures reached 40 degrees at 1880’ with ridgetop winds gusting into the low 20’s mph.  Temperatures dipped to the low 30’s overnight, winds stayed calm and just a trace of snow has fallen over the darkest hours of the night.

Today a low pressure system is making its way from the Gulf of Alaska toward the Susitna valley bringing us a chance for 3-5” of snow at 1,000’ as it moves through.  Winds will be light from the SE in the 12-20mph range with temperatures in the mid 30’s today dropping to the mid to high 20’s as this low pressure clears the Kenai Peninsula.  The potential exists for lingering snow showers to sea level by later this evening.

By Friday afternoon another low pressure and associated front will be moving into the Gulf spreading rain to coastal areas and snow showers to the higher elevations.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880')  34  1 .2   81
Summit Lake (1400')  36  0  .02 12 
Alyeska Mid (1700') 34   1 .2   39


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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812')  25  E  29
Seattle Ridge(2400')  27  n/a 11  22 

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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