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ARCHIVED - Forecasts expire after 24 hours.
Issued
Mon, March 9th, 2015 - 7:00AM
Expires
Tue, March 10th, 2015 - 7:00AM
Forecaster
John Fitzgerald
Avalanche risk The Bottom Line

The danger is MODERATE on steep wind loaded slopes in the Alpine.   Wind slabs up to 1 foot in depth could be triggered by skiers and riders on a variety of aspects and be large enough to injure or bury a person.   Loose snow avalanches could also be triggered in steep terrain sheltered from recent winds.

The danger is LOW in the treeline elevations, where avalanches are unlikely.

Special Announcements

Several close calls resulting in burials and rescues happened on Hatcher Pass yesterday.   Please visit hatcherpassavalanchecenter.org if you are planning on heading up there.   Dangerous conditions will likely continue at Hatcher Pass today.

Mon, March 9th, 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
  • Wind Slabs
    Wind Slabs
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.
More info at Avalanche.org

Winds yesterday out of the South and West loaded slopes that don’t typically get loaded.  Yesterday my partner and I watched this loading as it happened.  Some areas were sheltered enough by surrounding terrain which prevented this from occurring.  What this means is that there are now 1-2 day old wind slabs up to a foot in depth on a variety of aspects.  On Turnagain Pass steep upper elevation North and East facing terrain is suspect.  In the Girdwood Valley one large natural avalanche released over the weekend as a result of recent winds on a Southeast aspect.  Winds will continue generally out of the Northwest today in the 20 mph range, helping to slightly increase the size and sensitivity of slabs.

Cardinal directions aside, it is more important to be able to recognize wind loaded slopes before you are on them.  Snow that looks pillowy, feels stiff or sounds hollow should be approached with caution in steep terrain.  Shooting cracks and collapsing are sure signs that the snow is unstable.  Probing with a ski pole, hand pits, and feeling with your skis or board will allow you to assess the snow below your feet.  Avoidance of terrain over 35 degrees with recent wind loading will be important today.

West winds loading East aspects along Seattle Ridge March 8, 2015

wind loading Seattle ridge

Avalanche Problem 2
  • Dry Loose
    Dry Loose
Dry Loose
Dry Loose avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.
More info at Avalanche.org

Areas sheltered from the winds will be holding 3-8” of low density snow.  On sustained slopes over 40 degrees, expect human triggered sluffing to occur.  These sluffs should be low to medium volume and large enough to knock a person over.  This problem becomes more pronounced when traveling above terrain traps such as gullies, cliff bands or trees.

Weather
Mon, March 9th, 2015

Clear, cold and windy sums up the weather over the past 24 hours.   Cold air moved in behind the system that left new snow throughout the region.   Winds yesterday were strong and blowing out of unusual directions (see video).   Clouds moved in late in the day and left a skiff of new snow.

Today expect similar conditions.   Ridgetop temperatures will be in the single digits F.     Winds will be out of the Northwest at 15-20mph.   Thin clouds and light flurries this morning will give way to clearing skies by the afternoon.

Clear skies and cool temps are on tap for the first half of the week as high pressure gradually sets up over Southcentral Alaska.   Winds should diminish after today.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 17 0 0 44
Summit Lake (1400′) 17 0 0 9
Alyeska Mid (1700′) 19 0 0 28

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 7 WNW 9 41
Seattle Ridge (2400′) 12 W 19 53
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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.