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ARCHIVED - Forecasts expire after 24 hours.
Issued
Thu, January 15th, 2015 - 7:00AM
Expires
Fri, January 16th, 2015 - 7:00AM
Forecaster
Graham Predeger
Avalanche risk The Bottom Line

The avalanche danger is MODERATE today across the majority of the forecast area.   Wet loose and glide avalanches will be the primary concerns where rain has barraged the snowpack over the last 3-days. Above 3500′ where we have seen more snow than rain, the danger is CONSIDERABLE as storm snow has fallen on a slick, very supportable crust.   Wind slabs can be expected to continue to build in the 3 -5′ range on Westerly slopes throughout the day and may be reactive to human triggers.

Special Announcements

The CNFAIC Avalanche Rescue Workshop schedule for January 18th has been canceled due to lack of snow at the parking lot level in Turnagain Pass. The next hands-on rescue workshop is scheduled for Saturday February 7th.  Please check our  calendar  for up to date info.  

Thu, January 15th, 2015
Alpine
Above 2,500'
3 - Considerable
Avalanche risk
Treeline
1,000'-2,500'
2 - Moderate
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. Dangerous avalanche conditions. 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
  • Wet Loose
    Wet Loose
Wet Loose
Wet Loose avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.
More info at Avalanche.org

Another day of warm temps and steady rain continues to test our snowpack and our patience. Expect to put skis on at the snow line, around 1,500’ or higher.  Once on the snow, the primary avalanche concern will come in the form of wet loose avalanches as the pack at these lower elevations is quite saturated and lacks structure.  Several days of rain now has seasoned this elevation band and any wet loose avalanches should be a predictable problem encountered on steep (>35 degree) slopes.  Anticipate these wet loose avalanches and avoid terrain traps if you choose to continue ascending toward higher elevations and winter!  With increased elevation today through the rain zone, the potential exists to trigger a larger, wet (cohesive) slab avalanche where we have more structure in our snowpack.  I’d expect this to be more of an issue in the 2,500 – 3,500’ zone.

Avalanche Problem 2
  • 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

If you are still climbing and have hit the 3,500’ mark you’ll likely be very wet at this point.  We have very little info from upper elevations since this most recent storm hit.  What we do know is that 4 days ago there was a very supportable surface crust prior to 3”+ of water (estimated 30 – 40” of snow above 3500’) and high winds (40 – 80 mph from the East on Sunburst).  We lack info at this point to understand how well new snow is bonding to the pre-existing surface but expect to encounter fresh, potentially sensitive wind slabs on leeward slopes in the 3 – 5’ range above 4,000’.  It’ll be important to pay attention to any red flags (recent avalanches, cracking or whumphing), conduct your own stability assessment and exercise caution and conservative decision-making if travelling in the highest reaches of the forecast area today.  Dangerous avalanche conditions are likely to exist as we are still within an active weather pattern.

 

Additional Concern
  • Glide Avalanches
    Glide Avalanches
Glide Avalanches
Glide Avalanches are the release of the entire snow cover as a result of gliding over the ground. Glide avalanches can be composed of wet, moist, or almost entirely dry snow. They typically occur in very specific paths, where the slope is steep enough and the ground surface is relatively smooth. They are often proceeded by full depth cracks (glide cracks), though the time between the appearance of a crack and an avalanche can vary between seconds and months. Glide avalanches are unlikely to be triggered by a person, are nearly impossible to forecast, and thus pose a hazard that is extremely difficult to manage.
More info at Avalanche.org

Glide avalanches have been active across the Turnagain zone in steep terrain below 3,000’ since last weekend.  These have been observed littered across the eastern face of Seattle ridge, Eddies (including the final steep pitch on the SW Face), and Corn Biscuit.  Glide avalanches are impossible to predict when they may release so it’s best to simply avoid your exposure to any glide cracks as much as possible.  In channeled terrain, such as below Seattle ridge debris has been observed running out to as low as about 1,200’ (well below the ‘snow-line’).

Weather
Thu, January 15th, 2015

Yesterday marked the 8th day in a row of unseasonably warm temperatures across south-central Alaska with temps at Turnagain pass averaging 37 degrees.   Last night we saw perhaps the peak intensity of this most recent storm with hourly rainfall amounts in the .1 – .2 € of water/ hour from Turnagain pass to Girdwood.  Winds also picked up yesterday afternoon from the East with a max gust of 88mph at Sunburst.

Today looks to be more of the same with another 1 € or more of water forecasted, moderate winds from the east in the 20-40mph range and unseasonable warm (low 40’s @ 1000′) temperatures.   The rain/ snow line is expected to drop (from roughly 2500′) throughout the day as cooler air aloft filters into our region tonight and the possibility of a rain/ snow mix at 1000′ by the evening hours.

After this current disturbance exits our region this evening we can expect temps to dip slightly to more €˜near-normal’ by tomorrow and a chance of rain/ snow in the forecast thru Sunday.    

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 35     0   1.8  29
Summit Lake (1400′) 36    0 .38   5  
Alyeska Mid (1700′) 36    0 2.3    19

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′)  28 E   38 88
Seattle Ridge (2400′)  30 NNW   22   62  
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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.