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ARCHIVED - Forecasts expire after 24 hours.
Issued
Tue, April 30th, 2013 - 7:00AM
Expires
Wed, May 1st, 2013 - 7:00AM
Forecaster
Wendy Wagner
Avalanche risk The Bottom Line

Wow, what a feast or famine kind of winter season! The November and December famine was followed by a significant Holiday feast which lingered through February and by March it was back to famine through April. In fact, of the 322″ of snow that fell on Turnagain Pass, 252″ (28.4″ H20) fell between Christmas Eve and February 28th. November, most of December, March and April added up to a meager 70″ of snowfall (6.7″ H20). For the number geek out there: 78% of our snow fell during only 38% of the season. More details below in the season roundup.

This is being written on the last day of April and to date, April has been unusually cold and dry. This has delayed (and maybe even denied) the spring melt down or infamous shed cycle. But, we do have warmer and wetter weather moving in for the first few days of May. The snowpack is old and tired (only 10-18″ of snow for April…) yet it is still mostly dry snow and will undergo its transition to a summer snowpack at some point in May. Once the pack becomes isothermal (all the same temperature at 32deg F) it loses its strength. This is the phase when the snow becomes unsupportable and your boot sinks down several feet. At this stage the    

BOTTOM LINE: With a lot of cold dry snow remaining in the mountains, the potential for large wet avalanches will continue to be a very real concern through May.   The best way to mitigate this is watching for new avalanches, especially new large avalanches

Special Announcements

We are no longer issuing daily avalanche advisories for the 2012/13; however, this does not mean that the avalanche season has ended.

We would like send out a HUGE THANK YOU to  all of who have submitted observations  this year, they are invaluable to us, and help us steer this operation in the right direction.

We would also like to thank the  Friends of the CNFAIC. We would NOT be here without your support and hard work – THANK YOU! This amazing and selfless group has a tireless passion for keeping people safe in the backcountry.

Last but far from least, we would like to thank the following for sharing the valuable avalanche information that helps to greatly improve our forecasts:
-Alaska DOT
-Alyeska Ski Patrol
-Chugach Powder Guides
-Alaska Railroad
-Alaska Avalanche School
-Alaska Pacific University
-Everyone else who has contributed this season

Tue, April 30th, 2013
Alpine
Above 2,500'
0 - No Rating
Avalanche risk
Treeline
1,000'-2,500'
0 - No Rating
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
  • 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

                      

                            SPRINGTIME AVALANCHE TIPS – Timing is everything


Watch for the “shed cycle”. This typically lasts a couple weeks, begins on southerly slopes then moves to both east and west until finishing up on north. Keep an eye on the ridgetop weather stations for multiple days of above freezing overnight temperatures. This can signal a snowpack with limited refreezing and when followed by warm days (either sunny or rainy) can dramatically increase the likelihood of natural and human triggered large avalanches. Careful route planning to say out from under slopes with wet and rotten snow is essential during this period.

  • Once the snow has undergone the transition to a summertime pack and is freezing at night and warming during the day (the corn season),hitting the slopes early and getting off them when they become too sloppy is critical.. 
  • Mushy snow more than 6″ deep is a sign that it’s time to exit the area. Following the aspects as the sun heats up the slopes over the course of the day, east to south then west, can make for great riding/skiing days ending in sunny tailgateing. 
  • Keep in mind, cloud cover ‘holds in the heat’ and can dramatically limit overnight refreezing. A shallow to no refreeze will not only give daytime heating a jump start on weakening the pack, but can produce less than stellar riding conditions.
  • Beware for warm storms where rain is falling on snow. Especially when rain is falling on cold dry snow. This can quickly increase the avalanche danger.
  • After a new snowfall, watch for the first rays of sun to trigger both slab and loose snow avalanches in the new snow. Often, these initiate just below trees and rocks.
  • One of the easiest ways to stay safe in the springtime is knowing what kind of surface you are traveling on and under. Hard frozen snow, that easily supports a person and/or snowmachine, is unlikely to avalanche. Soft and saturated snow, deep enough to leave tracks you would not want to ski through when frozen, is a RED FLAG that the snow is losing its strength and becoming ripe to avalanche.
  • Last, don’t forget to plan your route back to the car. Does it take you under slopes that were frozen and safe earlier in the day, but now have been cooking in the sun waiting to slide on your return?
Weather
Tue, April 30th, 2013

SEASON WEATHER ROUNDUP
Check out our Weather History  page where you can find our monthly weather charts. Here is the  weather chart for April.


SNOWFALL and SNOW DEPTH –   (Turnagain Pass SNOTEL 1,880ft on Center Ridge)

Seasonal snowfall was 322“ (red line, Nov 1 – Apr 30) – a feast or famine regime. Last season snowfall was 385″ for comparison (blue line). Snow depth is shown in the graph below:

 
Don’t forget about the BeadedStream snow temperature array. It’s located near the SNOTEL site and will hopefully be up and running until June!

AIR TEMPERATURE –   (Sunburst weather station 3,812ft)

Sunburst weather station:



WIND –   (Sunburst weather station 3,812ft)
Sunburst had a much milder year for winds (compared to last season when we had record setting gusts). The mid-season stormy period is clearly evident in the increase in easterly wind from Dec 24th till the beginning of March.




Current weather can be found on the  CNFAIC weather page.


Thank you for checking the avalanche advisories this season. Have a great spring and summer!!

Observations
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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.
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