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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Wendy Wagner  
Tuesday, January 8th 2013
Created: Jan 8th 6:54 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.
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.
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The Bottom Line

A CONSIDERABLE avalanche danger exists above treeline today where human triggered avalanches are likely on slopes steeper than 35 degrees. We have a complex avalanche problem in the backcountry and any avalanche triggered today has the potential to be large and dangerous. Below treeline the danger is MODERATE where the likelihood is lower but the possibility remains for triggering a slide.


Primary Concern

It seems we are on the doorstep for clearing skies and a break in the past 15 days of stormy weather. If we don’t see the sun this afternoon we should by tomorrow morning. The good visibility should allow for travel out of the trees and into an enticing couple feet of fresh powder, which brings us to our primary concern – triggering a deep and dangerous slab avalanche.

To recap, we have had 122+” of snow fall in just over two weeks on very weak faceted snow formed in October and November. Large natural avalanches have been widespread along with one human triggered avalanche during these two weeks - all failing in the weak early season snow. Two deep slabs were pulled out yesterday with explosives and the low visibility kept any information hidden as to larger avalanches triggered by the 2-3’ of load added the past two days. The weak layer is now 4-8+’ deep and rarely giving us clues as to its instability – until it fails catastrophically. There is a lot of uncertainty as to how hard these deep slabs are to trigger at this point and we have very little information from above treeline. That said, these are potentially unsurvivable slides and warrant respect.

As we go into this clear period we cannot forget about this deeper weakness. Keeping terrain choices conservative, steering clear of large open committing slopes and slopes steeper than 35 degrees is recommended. Watching for and avoiding trigger points is also key – check out John’s great write up on that HERE. It is very easy to focus on the light powder, new wind slabs and forget about the dragon lurking below. This snowpack deserves patience.


Secondary Concern

The winds that have been blowing out of the east have died down overnight and should switch to a northwest direction today. There are likely a few lingering wind slabs from yesterday that have not stabilized yet to watch out for. These could be in the 1-4’ deep range. Also, due to the shift in wind watch for fresh slabs on easterly slopes (i.e., Seattle Ridge). Keeping an eye out for stiffer feeling snow as well as cracking and collapsing in the new snow are good clues as to finding a wind slab. There is also the possibility a wind slab could step down and trigger a deeper slab so be aware of the terrain you are in and how committing it is.


Mountain Weather

Snow totals at Turnagain Pass in the last 48 hours are 22”, the past 24 hours has seen roughly 8-10”. Expect higher amounts above treeline. Winds during the snowfall have been easterly averaging 20-30mph, gusting to the upper 40’s during this period while temperatures have decreased a few degrees and are near freezing at sea level this morning.

Today snow showers will continue to taper off and skies begin to clear as the low pressure it the Gulf moves east. There is a chance for an additional trace-2”. Winds have died down dramatically overnight and will shift to the NW through the day picking up to 20mph on the ridges by this afternoon. Temperatures look to remain in the low 20’s F above treeline and low 30’s below.

A short lived ridge moving over us tomorrow will bring a break in the weather and our first dose of sunshine since just before Christmas Eve. An unsettled westerly flow will bump us back in the clouds and snow for Thursday and through the weekend.

 


Kevin will issue the next advisory on Wednesday, January 9th.

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: Nov 18, 2017 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: Closed
Placer River: Closed
Skookum Drainage: Closed
Turnagain Pass: ClosedOnly a few inches of snow sits at the motorized lot, not enough to open for snowmachining at this time. Updated Nov. 18, 2017
Twentymile: Closed
Seward District
Carter Lake: Closed
Lost Lake Trail: Closed
Primrose Trail: Closed
Resurrection Pass Trail: ClosedResurrection Pass trail is expected to open to snowmachine use during the 2017/18 winter season.
Snug Harbor: Closed
South Fork Snow River Corridor: Closed
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.


USFS SNOW AND AVALANCHE HOTLINE (907) 754-2369
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