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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Graham Predeger  
Thursday, February 21st 2013
Created: Feb 21st 6:29 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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Special Announcement

The Chugach National Forest is looking for your comments in the Forest Plan Revision Process.  Public meetings are being held this week and next in Seward, Soldotna, Anchorage, Cooper Landing, Moose Pass Cordova and Valdez.  Forest Managers and decision makers are anxious to hear input from the people who live, recreate and make a livlihood on the Chugach National Forest.  For more information and meeting dates click here.


The Bottom Line

With little new snow and wind overnight, the avalanche danger rating above treeline has dropped to MODERATE.  Below treeline the danger remains MODERATE.  This means that human triggered avalanches are possible today and will most likely be confined to storm snow at all elevations or fresh wind slabs that built early yesterday morning, mainly above treeline.  Additional avalanche concerns today come in the form of persistent slabs as this latest storm further adds weight to known weak layers in our snowpack.


Primary Concern

Today looks to be the classic “Day after the storm” day.  Storm totals were in the 1 foot range at mid-elevations with snow falling down to sea level.  The winds, though potent at the beginning of the storm lessened around noon yesterday.  As we are still within the 24-hour window directly after a storm, expect this most recent layer of storm snow to be touchy today, particularly in steeper terrain.  Very little information is known above treeline as to how well storm snow is bonding given difficult travel yesterday, but we can assume tender wind slabs at higher elevations, chiefly below ridges and on west facing (leeward) slopes.  These wind slabs may be covered up with a fresh coat of white given the lack of wind during the latter half of the storm. 

Storm snow at around 1000’ did exhibit an upside down character and several point releases were observed where denser, surface snow was sliding on slightly older less dense snow.  As this snow settles out today, I’d expect slabs to become more cohesive at lower and mid elevations where they may be reactive to a skier or snowmachine. 


Secondary Concern

We continue to monitor a couple of known bed surface/ weak layers within our snowpack.  The first is a series of crusts/ facet combinations formed in late January.  Crusts are inherently slow to “heal” once buried and can act as a slick bed surface, promoting weak layers (facets) to form and persist for several weeks or more.  The good news is that this crust is only present in a rather concentrated elevation band between 1900-3000 feet.  The bad news is that crusts are persistent by nature and prove difficult to forecast for.

Then we have the deep slab issue that reared its head south of the Summit Lake region near Carter Lake on Monday.  Though we have not seen recent signs of deep slab instabilities in the Girdwood or Turnagain region recently, this incident is a good reminder that weak, basal snow does exist region-wide and is more easily triggered in shallow areas where a skier or snowmachiner can influence the bottom of the snowpack.


Mountain Weather

This latest storm came in like a Lion and left like a Lamb.  Easterly winds, most intense Tuesday evening as the front impacted our region brought around a foot of snow to mid-elevations yesterday, with higher elevations and some localized spots seeing more.  Winds abated substantially during the later half of the storm as ridgetop temperatures briefly spiked around 1 PM.

An additional 1-2 inches of snow is expected today at all elevations as a weak low pressure slowly moves over our region.  Winds will be in the 5-10 mph range from the southeast.  Looking out toward the weekend there is a chance of snow everyday through Sunday as another front moves into the Gulf of Alaska.


Fitz will issue the next advisory on Friday, February 22st.

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.

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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
If you have comments or questions regarding CNFAIC operations or winter recreation management, please email staff@chugachavalanche.org
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