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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Heather Thamm  
Friday, March 20th 2015
Created: Mar 20th 6:21 am
3 Considerable Alpine / Above 2,500' Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision-making essential.
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'
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The Bottom Line

The avalanche danger for Turnagain Pass is CONSIDERABLE in the Alpine where triggering a slab 3’ thick will have high consequences. Avoid slope angles steeper than 35° and be aware of decision-making traps that may trick you into thinking the conditions are more stable than they are.

The avalanche danger is MODERATE at Treeline. A near surface crust has formed below 2500’ making the snowpack at this elevation more stable. However there is still water draining through the snowpack at this elevation and if temperatures reach the mid 40’s today, wet-loose avalanches could be an additional concern. 


Primary Concern

In the Alpine above 2500’ a slab 2-3’ has formed over the last four days. The majority of this snow fell on March 16th, but strong Northeast winds and additional precipitation have likely made slab depths closer to 4-5’ on leeward starting zones. Below this slab lies weak faceted snow sitting on a crust bed surface. This weak layer was very touchy on Tuesday, but as we move away from the initial loading event the slab has become denser and more supportable. The scary part about this avalanche problem is if the right trigger point was found the consequences could be very serious. Obvious signs like shooting cracks, collapsing and natural avalanches might not be present today making it easier for us humans to be lured into steeper terrain.

Today’s travel advice is simple: Avoid traveling in steep terrain and keep your slope angles under 35°.

The combination of sunny beautiful weather following a four-day storm cycle is our biggest hazard today. It will be tempting to venture into bigger terrain making it easy to “talk yourself” into thinking the conditions are more stable than they really are. Here are some classic traps to be aware:

“Someone just skied that line and it didn’t slide.”

“I’ve skied this slope a 100 times and I’ve never seen it slide.”

“Our snow pit results were good, therefore this slope must be safe.”

“I just heard/felt a “woomph”, but my partner has a lot more experience than I do and he/she doesn't seem to be concerned.”

 


Secondary Concern

Two days of Northeast winds averaging 30-40 mph have loaded South and Western slopes and fresh wind slabs up to 2’ thick could be easy to trigger on leeward features. If a wind slab is triggered it could be enough force to initiate the larger problem described above. This will be an additional reason to avoid steep terrain.

 


Additional Concern

If temperatures reach the mid 40’s F as forecasted for today, wet point-release avalanches on sun-exposed slopes are possible. They will likely be seen on steep Eastern aspects first and then on Southern aspects as the Sun moves throughout the day. 

There is currently a lot of water draining through the snow pack at mid elevations and temperatures could be warm enough to start meling the newly formed surface crust. It is possible that a small point release from the Alpine could pick up enough volume and momentum to entrain wet snow at this elevation band. Today might be a good to day to avoid places like Seattle Ridge where access into and out of the Alpine is on a steep Eastern slope.

Yesterday large puddles and flowing water were observed near the road along the Seward Hwy in Turnagain Pass.


Mountain Weather

Yesterday we received 0.7” of water in Turnagain Pass. Rain/snow line was near 1500’ and temperatures below this elevation averaged in the mid 30’s F. At higher elevations temps were in the mid to high 20’s F and snow accumulation was likely around 7”. Winds were 30-40mph from the Northeast along ridgetops.

Overnight skies cleared and no new precipitation fell. Temperatures dipped into the low 30’s F at mid elevations and NE winds were 15-20 mph. 

Today will be mostly sunny and day-time temperatures could reach the mid 40’s F. Ridgetop winds will be 5-15 mph from the East and no new precipitation is expected today.

Tomorrow there is a chance for rain showers at lower elevations. Temperatures are expected to remain warm, high 30’s to mid 40’s near sea level. This could mean snow in the upper elevations, but not much accumulation is expected. Winds will be light to moderate from the East along ridgetops.     



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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 33  .7  56 
Summit Lake (1400') 34  .1  12 
Alyeska Mid (1700') 34   0 .22  35 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 25  ENE  22  68 
Seattle Ridge(2400') 27  NW  18  50 

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: Mar 28, 2017 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: OpenPlease park on road in and leave the turnaround (near outhouse) open for trailers to turn around.
Placer River: OpenPlacer remains open but SKOOKUM DRAINAGE will close to motorized use on April 1st.
Skookum Drainage: OpenSKOOKUM DRAINAGE CLOSES TO MOTORIZED USE ON APRIL 1 annually as per the Chugach National Forest Plan document.
Turnagain Pass: Open
Twentymile: Open
Seward District
Carter Lake: Open
Lost Lake Trail: OpenPlease STAY ON existing and hardened trail surface through the lower sections of this route.
Primrose Trail: OpenPlease STAY ON existing and hardened trail surface through the lower sections of this route.
Resurrection Pass Trail: ClosedClosed for 2016/17 winter season. This is a non-motorized season. This alternates every other year and will open again during the 2017/18 winter.
Snug Harbor: Open
South Fork Snow River Corridor: Open
Summit Lake: Open

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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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