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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Wendy Wagner  
Sunday, March 25th 2012
Created: Mar 25th 6:59 am
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.
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The Bottom Line
Good morning. This is Wendy Wagner with the Chugach National Forest Avalanche Information Center on Sunday, March 25th at 7am. This will serve as 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).

BOTTOM LINE
There are pockets of CONSIDERABLE danger on southerly aspects for wet avalanches later in the day in areas with direct sun. Additionally, there are pockets of CONSIDERABLE danger on slopes that were wind loaded during the storm Friday night into Saturday. These wind slabs are most likely found on N and W aspects above treeline and suspect to remain likely to trigger today where they are sitting on either wind or sun crusts with weak snow between. CNFAIC Staffwise, there is a MODERATE danger where slab avalanches and sluffs are possible on any slope greater than 35 degrees.

AVALANCHE DISCUSSION
The 6-10+" of snow that fell Friday night through Saturday came in 'upside down', due to the increasing temperatures during the storm, creating an unstable storm layer. This new upside down layer fell on top of a sun crust on many east, south and westerly aspects which provided a nice bed surface (the third ingredient for a slab avalanche: slab, weak layer, bed surface). What resulted were many soft slab and wind slabs that were triggered both naturally and by people. I remotely triggered one small slab on a SSE facing slope from 150 feet away. Many of these were shallow due to the modest amount of snow but they were able to propagate quite well. Slabs were also reported on northerly aspects where SE winds likely formed sensitive wind slabs. The sun got to the snow later in the day and wet loose slides began to run in the later afternoon.

Concern #1 - Wet Avalanches
Watch for small to medium, to even large, wet loose avalanches on southerly slopes later in the day today. If the sun comes out in full force it will quickly warm and destabilize the new snow, especially on and under rocky/vegetated slopes. With winds light to non-existent and temperatures WARM, this will add to the impact of the sun that we have not seen the past few weeks.

Concern #2 - Wind Slab and Soft Slab
Today, wind slabs that formed during the storm and soft slabs should be settling out and not quite as easily triggered as they were yesterday. However, they are still POSSIBLE to trigger and there are areas where the new snow fell on surface hoar and in these locations they will still be LIKELY to trigger by a person. These slabs should be fairly shallow, except where winds have deposited snow in deeper slabs on leeward slopes. Additionally, they could have the potential to step down and break into larger avalanches where buried weaknesses exist. Keeping a close eye out for recent avalanches and cracking in the snow around you will be bulls eye clues the snow is still grumpy and unstable.

Concern #3 - Persistent Slab
We still have two weaknesses that reside deeper in the pack: buried surface hoar and facets above a sun crust. The buried surface hoar is 2-3' deep now and, as Kevin found out a couple days ago, still reactive. Larger avalanches are possible on northerly aspects where a person, or a smaller avalanche could trigger a failure in this deeper layer. Southerly aspects are fairly well tied together with several crusts now but there is one crust that is still producing clean shears about 2-3' down. If we get very warm temperatures that soften the upper crusts this deeper layer could become reactive, again producing larger and more dangerous avalanches.

MOUNTAIN WEATHER
By mid-day yesterday the snow showers moved out and sunny skies moved in. Temperatures climbed through the storm, and kept climbing as the sun came out, to top out in the low 30's around treeline and near 20F on the ridges. Winds blew from the East in the 30-40mph range with the snow overnight then dropped off to under 10mph as they turned northwesterly during the day. Storm totals Friday evening through Saturday were roughly:
Turnagain Pass - 5-8"
Girdwood Valley - 6-10"
Summit Lake - 2-3"

Today, partly cloudy to sunny skies are in store with a chance for a flurry or two with clouds moving in and out. Temperatures are forecast to be WARM, mid to upper 30's near treeline and mid 20's on the ridgetops. Northerly winds should remain light on the peaks, blowing 5-10mph.

CNFAIC Weather Page and the NWS forecast

Chris will issue the next advisory Monday morning. If you get out in the backcountry we want to know what you are seeing. Please send us your observations using the button at the top of this page or give us a call at 754-2369. Thanks and have a great day.

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: Apr 28, 2017 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: Closed
Placer River: Closed
Skookum Drainage: ClosedSKOOKUM DRAINAGE CLOSED TO MOTORIZED USE ON APRIL 1 annually as per the Chugach National Forest Plan document.
Turnagain Pass: OpenOpen thru May 14th.
Twentymile: Closed
Seward District
Carter Lake: OpenClosed May 1.
Lost Lake Trail: OpenClosed May 1.
Primrose Trail: OpenClosed May 1.
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: OpenClosed May 1.
South Fork Snow River Corridor: OpenClosed May 1.
Summit Lake: OpenClosed May 1.

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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