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Avalanche Advisory

Turnagain Area Avalanche Advisory
Saturday, April 14th 2018 6:12 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 is LOW this morning and will rise to MODERATE today. Triggering a small to large wet avalanche will be possible at all elevations in the afternoon. In the Alpine, triggering a slab avalanche 1-2’ thick remains possible where drier snow exists, and will become possible on Southerly slopes when the surface crust melts. Give cornices extra space. 


 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.
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

The snow is melting fast at lower elevations and the following areas have been closed to snow machining on the Chugach National Forest: Twenty mile, Snow River, Primrose, Lost Lake. Snug Harbor access to Lost Lake remains open at this time. Keep an eye on the riding status at the bottom of the page for other areas. 

Be aware some summer hiking trails like Byron Glacier trail in Portage have steep avalanche terrain above them and the potential for a natural avalanche exists later in the day on slopes getting lots of sun in the afternoon. 

CNFAIC is transitioning to spring time hours in preparation for the end of the season in two weeks. Beginning Monday, we will issue forecasts 4 days/wk on Sat, Sun, Tue, Thur. The final forecast will be on April 28th. You can check out springtime tips on the final Summit Summary HERE. 


Avalanche Problem 1

Wet Loose

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
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Size

Wet Loose: Spring is here and with it comes daily fluctuations in the avalanche danger with sun and warming. Timing is everything. Clear skies overnight have created a surface crust adding strength to the snow. As the day heats up and the crust melts and loses strength, the danger rises - making it possible to trigger a wet avalanche on steep sun exposed terrain features. Today looks similar to yesterday with daily temperatures expected to reach the mid-40F’s by early afternoon and little to no wind. Remember solar noon is around 2pm  and this is when wet avalanches can begin to release, either naturally or by a person. Once the snow becomes wet and 'mushy' and your skis or snowmachine start trenching into wet snow, it's time to find supportable surfaces. Even a small wet avalanche can turn into something larger in bigger terrain.

Wet Slab: There remains some uncertainty around the possibility of triggering a wet slab avalanche as warm temps today make the snow wet in the mid elevations. Earlier this week many natural wet loose and wet slab avalanches occurred below 2000' where rain saturated the snowpack. As water drains out of the snow and we experience several days of re-freezing overnight this is becoming less likely, but not out of the question.

Cornices: Daily warming and sunnier weather can make cornices more unstable. As always, give cornices plenty of space and limit exposure underneath them.

Widespread natural wet avalanche cycle occurred below 3000' throughout our region. Note the wet slab at 1500' on South face of Tincan. 

 

Pay attention to how supportable the snow feels in the afternoon as surface crust melt and the snow becomes wet. Yesterday it was easy to post hole up to your waist on Southerly aspect below 2000'. 

 

Most of the large wet avalanche from 4/10-4/11 on Seattle Ridge were on the Southern end of Turnagain Pass where a generally thinner snowpack exists. Some of these avalanches released near the ground. 

  


Additional Concern

Persistent Slabs

Triggering a lingering storm slab or a persistent slab is becoming less likely with time. However afternoon warming adds an element of uncertainty as surface crusts break down and destabilize the snow on solar aspects. Yesterday a group of 3 skiers experienced a collapse (whumpf) at 3000’ on a SW aspect of Tincan, and the day before a skier triggered a storm slab on a West aspect of Johnson Pass near 4900’. We know of older weak snow (facets) buried within the top 2’ of the snowpack and we don’t have a lot of info about how this snow is adjusting in the upper elevations. Northerly aspects with dry snow (without a surface crust) may harbor this set up. Basically triggering slab avalanche 1-2’ deep should still be on your mind if venturing into steeper terrain in upper elevations.  


Mountain Weather

Yesterday was clear and sunny and no precipitation was recorded. Temperatures reached 50F near sea level and mid 40F’s in the mid elevations. Ridgetops were in the mid 30F’s during the heat of the day. Temperatures crept into the upper 20Fs at ridge tops and mid 30F’s at lower elevations. Winds were light from the Northwest 5-15mph. 

For today expect sunny skies and another warm day. Temperatures should again reach the low 50F below 1000’ and 40F’s along ridgelines. Winds will be calm to light (0-10mph) from the NW. Temperatures are expected to be in the low 30F’s overnight. 

For Sunday and Monday sunny weather will remain with diurnal temperatures swings, cooling overnight and warming during the day . Ridgetop winds are supposed to remain light from the Northwest. There is a possibility for light rain starting Wednesday associated with a low-pressure developing near the Aleutians. 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 41  68 
Summit Lake (1400') 37  24 
Alyeska Mid (1700') 40  65 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 31  NW  15 
Seattle Ridge(2400') *N/A  NW   5 21 

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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