Avalanche Advisory

Turnagain Area Avalanche Advisory
Tuesday, February 18th 2014 7:00 am by Wendy Wagner
ARCHIVED ADVISORY - All advisories expire after 24 hours from the posting date/time.
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The Bottom Line

The avalanche danger is CONSIDERABLE this morning and expected to increase to HIGH throughout the day on all aspects above treeline. Heavy snow accompanied by strong wind is in the forecast - the NWS has issued a Winter Storm Warning with up to 1-2 feet of snow accumulating through the day and into tonight. Natural avalanches are likely and have the potential to break into buried weak layers making for larger and more dangerous slides. The danger below treeline will rise to CONSIDERABLE where natural loose snow avalanches are expected along with the possibility for slabs around 2' deep.

**Dangerous avalanche conditions are on the rise in the backcountry and travel in avalanche terrain is NOT recommended. This includes avoiding runout zones and valley bottoms.

 Show the Complete North American Avalanche Danger Scale
4 High Alpine / Above 2,500' Travel Advice: Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
3 Considerable Treeline / 1,000'-2,500' Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision-making essential.
3 Considerable Below Treeline / Below 1,000' Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision-making essential.
Special Announcement

Motorized access via Turnagain Pass and Johnson Pass on the Glacier Ranger District of the Chugach National Forest are now OPEN.  Check the bottom of this page for the latest updates on riding area status and conditions as well as the Chugach National Forest website.

Avalanche Problem 1

Another round of snow is expected to come in fast and furious today. Winds, combined with high snowfall rates will rapidly load slopes and quickly increase avalanche danger. If the forecast verifies, instability will be on the rise for all the classic storm snow avalanche concerns:

Wind slabs:
Winds out of the East are currently increasing. With ample snow available for transport, naturally occurring wind slab avalanches 1-3' thick are possible on leeward slopes and rollovers, also watch for cross-loading in gullies. I'd expect much of today's avalanche activity to be in the form of wind slabs of varying thickness.

Storm Slabs:
Snowfall today will be falling on low density powder from Sunday night. Though today's snow is expected to be low density as well and not prime conditions for creating storm slabs, the simple "rapid loading" that is expected has the potential to do this - even without the presence of wind. These slabs will be soft and could occur naturally on steep slopes at all elevations.

Loose Snow avalanches:
Loose snow sluffs should be expected. The biggest concern with these is the possibility for initiating either a storm slab or a persistent slab on the descent.

Today will be ideal cornice growth and calving conditions. The main concern with cornices also has to do with the possibility for triggering a larger slab below.

*Note: The AKDOT webcam is working again on Turnagain Pass!  Keep tabs on snowfall as well as the road conditions with this link.

Avalanche Problem 2

Today we will be adding yet another load to our tenuous snowpack and potentially overloading the weak snow that sits just above the thick January crust. This weak layer of faceted snow has been well documented over the past two weeks and sits below all the February storm snow - between 2 and 3 feet deep. These persistent slab avalanches have the ability to propagate over entire slopes and be around 2-3' deep (deeper with any additional snow).

In the event the storm today does not produce, this avalanche problem will be the primary concern. We have already seen multiple large remotely triggered slides occur in this mid-pack weak layer and today will be no different.

Mountain Weather
Updated storm totals beginning Sunday evening through yesterday mid-day:
   Turnagain Pass - 14" (Eddie's), 12" (Tincan) and 10" on (Sunburst)
   Girdwood Valley mid to upper elevations - 8-9"
   Summit Lake - 3-5"
During the past 24-hours we have seen a short break between storms. Temperatures have hovered in the mid-teens on the ridgetops and mid-20's at 1,000'. Ridgetop winds have averaged 10mph with a max gust of 32mph from the East and Southeast. Overnight, clouds have filled back in with the beginning of the next system, which is on our doorstep.
Today and into tonight another round of heavy snow (1+" of water weight) is on tap. As of 6am this morning 4" has fallen on Turnagain Pass with only ~2" in Girdwood and a trace at Summit Lake. We should see between 10-18" by tonight - at least on the Pass. Ridgetop winds are just beginning to increase and are expected to average around 40mph from the East. Temperatures look to remain in the mid to lower teens above treeline and the mid-20's at 1,000', which will allow for snowfall to be low density.
Snow showers should taper off tomorrow (Wednesday) and models show a break between storms Thursday before another system moves in Friday with snow possible. 

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: Oct 05, 2019 )

Glacier District
Johnson Pass: ClosedClosed
Placer River: ClosedClosed
Skookum Drainage: ClosedClosed
Turnagain Pass: ClosedClosed
Twentymile: ClosedClosed
Seward District
Carter Lake: ClosedClosed
Lost Lake Trail: ClosedClosed
Primrose Trail: ClosedClosed
Resurrection Pass Trail: ClosedClosed. Will be open for the 2019/20 season pending adequate snow cover.
Snug Harbor: ClosedClosed
South Fork Snow River Corridor: ClosedClosed
Summit Lake: ClosedClosed

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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.

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