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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Wendy Wagner  
Saturday, March 23rd 2013
Created: Mar 23rd 6:39 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.
1 Low Treeline / 1,000'-2,500' Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
1 Low Below Treeline / Below 1,000' Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
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Special Announcement

One week from tomorrow is the 2nd ANNUAL CORN HARVEST - get it on your calendar now !! Come join the CNFAIC Friends and Forecasting staff on Turnagain Pass for free food, games, prizes, etc. This is one way we would like to thank all of you for your dedication and support. Oh, did I mention, it’s FREE?


The Bottom Line

There is a MODERATE avalanche danger today above treeline for wind slab avalanches. These will be soft, shallow and possible to find and trigger in areas that received 6 inches or more of new snow yesterday. Slopes most suspect are steeper than 35 degrees on west and southerly aspects where fresh wind deposited snow exists over the top of a crust. Areas that picked up less than 6 inches of snow, including below treeline, the danger is LOW where triggering an avalanche remains unlikely.


Primary Concern

Yesterday was our first chance in just over a week for a dose of fresh snow to cover the plethora of old tracks. We did get enough to do so in some locations but not quite enough in others. Most stations are reporting around 5-6” of low desnity snow (thanks to our cold temperatures) in the past 24 hours. A bit more can be expected at the higher elevations as well as in favored areas such as the northern side of Turnagain Pass and the Girdwood Valley.

Winds associated with yesterday’s snow were moderate from the east and having an easy time blowing the light snow into shallow drifts and soft slabs. This wind deposited snow has covered up all types of old surfaces such as sun crusts, wind crusts, old wind slabs and near surface facets (old soft powder). All of these surfaces will inhibit good initial bonding of the new snow. Wind slabs today should be soft and in the 4-12” range depending on how much snow fell in the area you are traveling. Watching for wind drifted snow and new snow that cracks out from your sled, board or skis will be the key. Expect any slide triggered on a crust or hard surface to run fast and far.

Additionally, watch for soft slabs in wind sheltered areas. The warming temperatures overnight will cause the loose snow from yesterday to bond forming an upside down layering. This warming will eventually help the new snow to stick to the underlying surfaces but, there is a window where the new snow becomes more reactive first. Keep this in mind in areas with greater amonts of snowfall.

Below is an image of cracking in a small fresh wind slab from yesterday - something to watch for today.

If you are traveling in the Summit Lake area old wind slabs are a concern. Check out the Summit Advisory as well as Fitz and Kevin's observation from yesterday.


Secondary Concern

Any new snow will easily slide on the old surfaces - especially where a crust sits underneath. Triggering a sluff is most concerning where new snow amounts are ~6” or greater.

Additional Concerns:
Don’t forget about steering clear of looming cornices. The temperature has gone up significantly in the past 24 hours at the upper ridgetops and this will increase the likelihood of cornice failures.

Surface Conditions:
Needless to say, the surface conditions are a bit variable with scoured areas alongside soft wind drifts. The best riding is likely in wind sheltered locations where a few inches of new snow on a crust or soft old snow can be found.


Mountain Weather

After 7 days of clear skies, yesterday a weak low pressure moved in from the west and we were back to snow and low visibility. During the past 24 hours we have picked modest amounts of low density snow:

-          Turnagain Pass –   ~5” (.4 water equivalent)
-          Alyeska –  ~5” (0.34 water equivalent)
-          Summit Lake – ~3” (0.3 water equivalent)
-          Hatcher Pass is reporting around a foot, maybe more. Check out the Hatcher Pass Avalanche Center if you are thinking of heading that way.

Winds have been out of the east predominantly in the 25mph range with gusts to 40 but have decreased overnight and shifted to a more southerly direction. Temperatures have been warming steadily from this time yesterday - Ridetops from ~10F to ~20F and 2,000’ from the mid-teens to mid 20’s.

Today we can expect cloudy skies with intermittent snow showers as yesterday’s system moves out. Accumulations today should be a trace to an inch. Winds will be out of the southeast at 5-10 mph with gusts to 15. Temperatures look to remain mild, in the mid to upper 20’s F at 1,000’ and 20F near on the Ridgetops.

Another low is heading to our south by Sunday bringing another chance for precipitation Sunday into Monday.

The Sunburst weather station should be up and running by Monday or Tuesday. There are some modifications with the webcam being done and it seems a fuse has been blown in the midst.

 


Fitz will issue the next advisory tomorrow morning, March 24th.

 

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: Dec 08, 2017 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: Closed
Placer River: Closed
Skookum Drainage: Closed
Turnagain Pass: ClosedRain and snow have fallen in Turnagain Pass this week, but not enough to open for snowmachining. Continue to check back to this site for updates.
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

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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