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Archives
ARCHIVED - Forecasts expire after 24 hours.
Issued
Tue, January 6th, 2015 - 7:00AM
Expires
Wed, January 7th, 2015 - 7:00AM
Forecaster
John Fitzgerald
Avalanche risk The Bottom Line

The general avalanche danger is LOW in many locations above 2,500′.   The possibility still exists for humans to trigger avalanches 1-3′ deep on very steep slopes and in areas with a shallow snowpack.   In these areas within the Alpine the avalanche danger is MODERATE today.

The danger at treeline is LOW where avalanches are unlikely.

Special Announcements

Join us for our final Fireside Chat this Thursday, January 8th,  in Anchorage! Topic: Mountain Weather and Snowpack.   CNFAIC forecaster and resident meteorologist Wendy Wagner will be taking a close look at the current state of the snowpack at Turnagain Pass along with a look into “when is it going to snow?”.   Cost is $0.

Tue, January 6th, 2015
Alpine
Above 2,500'
2 - Moderate
Avalanche risk
Treeline
1,000'-2,500'
1 - Low
Avalanche risk
Below Treeline
Below 1,000'
0 - No Rating
Avalanche risk
0 - No Rating
1 - Low
2 - Moderate
3 - Considerable
4 - High
5 - Extreme
Avalanche risk Avalanche risk Avalanche risk Avalanche risk Avalanche risk
Travel Advice Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features. Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern. Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding, and conservative decision-making essential. Very dangerous avalanche conditions. Travel in avalanche terrain not recommended. Extraordinarily dangerous avalanche conditions. Avoid all avalanche terrain.
Likelihood of Avalanches Natural and human-triggered avalanches unlikely. Natural avalanches unlikely; human-triggered avalanches possible. Natural avalanches possible; human-triggered avalanches likely. Natural avalanches likely; human-triggered avalanches very likely. Natural and human-triggered avalanches certain.
Avalanche Size and Distribution Small avalanches in isolated areas or extreme terrain. Small avalanches in specific areas; or large avalanches in isolated areas. Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas. Large avalanches in many areas; or very large avalanches in specific areas. Very large avalanches in many areas.
Avalanche Problem 1
  • Persistent Slabs
    Persistent Slabs
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.
More info at Avalanche.org

We have moved into a time period where buried weak layers have become very difficult to trigger.  Time and settling of the snowpack has allowed layers of buried surface hoar and facets (1-3 feet deep) to adjust and become less reactive.

The makeup, or structure of the snowpack is such that should an avalanche occur there is still potential for entire slopes to release.  Testing of these layers over the past few weeks has shown this potential.  

Slabs that built up on top of these layers have become very strong.  These slabs can withstand a lot of weight and force.  This is another contributing factor to the low likelihood of triggering an avalanche.

Areas where you could trigger an avalanche today include slopes over 40 degrees, convexities and slopes with a shallow snowpack.  The Girdwood Valley and Summit Lake areas have, in general thinner snowpacks than Turnagain Pass.  Thin spots can still be found throughout the forecast area and are worth avoiding.  Given the current hardness of slabs it is important to keep in mind that slabs can break above you and be very difficult to ride or ski off.

If venturing onto steep terrain practice good travel habits:
Expose only one person at a time
Utilize islands of safety for spotting and re-grouping
Identify escape routes in the event of a slab releasing
Communicate route decisions and plans within your group effectively
Be aware of groups above and below you and avoid exposing those groups to avalanche hazard

Weather
Tue, January 6th, 2015

Yesterday was another day of clear and calm conditions.   No new precipitation fell.   Winds were light coming out of the Eastern half of the compass.   Temperatures were on the cold side, with ridgetops in the teens-20’s F and some valley locations remaining in the single digits F under an inversion.

Today will be more of the same.   Temperatures at ridegtops will be in the 20s F and some valleys will remain in the single digits.   Winds will be light out of the East at 5-10mph.

The ridge of high pressure that is currently parked over much of mainland Alaska looks to begin breaking down by Wednesday night.   Clouds, warming temps and precipitation will move in as we near the weekend.

*Sunburst data is 3pm-6am due to temporary station malfunction

PRECIPITATION 24-hour data (6am – 6am)

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 21 0 0 33
Summit Lake (1400′) 3 0 0 6
Alyeska Mid (1700′) 21 0 0 25

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 22 ESE 4 11
Seattle Ridge (2400′) 19 E 9 20
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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.