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Issued
Wed, May 1st, 2013 - 7:00AM
Expires
Thu, May 2nd, 2013 - 7:00AM
Forecaster
Wendy Wagner
Avalanche risk The Bottom Line

Wow, what a feast or famine winter! We had a fairly late start to the year with an early season dry spell but, the Holiday onslaught delivered the goods – thankfully. And, even though the spring was dry as well, great riding and skiing was at hand during March and April.   More details below in the season roundup.

This is being written on the last day of April, which has been unusually cold and dry. The cold weather 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 beginning of May. The snowpack may be old and tired (only 10-18″ of snow for April…); however, it is still mostly dry snow and will undergo its transition to a summer snowpack at some point soon. It is this transition that we are concerned about, which is associated with the first week or two when the pack turns isothermal (the same temperature at 32deg F) and loses much of its strength.

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 – see below for some SPRINGTIME TIPS.

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

Additionally, THANK YOU to all of you who have supported the CNFAIC through donations and a variety of other means. This is the foundation we are building upon.

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

Our annual report will be posted in early May so watch for that on our resources page.

Wed, May 1st, 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”. One great way (and an old timer rule of thumb) is to keep an eye on the ridgetop weather stations. Avalanche activity often follows multiple consecutive days (usually 3) of above freezing overnight temperatures. This can signal a snowpack with limited refreezing and when followed by warm days (either sunny or rainy) dramatically increases the likelihood of natural and human triggered large wet avalanches. Careful route planning to stay out from under slopes with wet and rotten snow is essential during this period. See below for some additional general springtime tips:

  • 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.

  • Watch the CORNICES, these are large and likely to keep peeling off for a while.
  • 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
Wed, May 1st, 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“ (Nov 1 – Apr 30) – in a feast or famine regime. Last season snowfall was 385″ for comparison. In fact, of the 322″ of snow that fell on Turnagain Pass, 252″ (28.4″ H2O) fell between Christmas Eve and February 28th. Compared to a meager 70″ of snowfall (6.7″ H2O) that fell during November, most of December, March and April combined. For the number geeks out there: 78% of our snow fell during only 38% of the season.

Snow depth is shown in the graph below:

 
Don’t forget about the BeadedStream snow temperature array. This shows snowpack temperature vertically every 10cm (4″) and is great for watching the pack turn isothermal.   It’s located near the SNOTEL site and will hopefully be up and running until June!

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

A generally cool season all in all. The early season cold period (Nov-Dec) produced 2-3 feet of faceted snow and subsequently became quite reactive in late December and January once it was buried by the holiday onslaught. There were several large avalanches, including two close calls (Tincan and Repeat Offender). Additionally, the mid-season stormy period was interrupted by a couple days cold snap in late January. The cold snap followed 2 days of rain to 2,500′ (late January crust) and is responsible for the weak snow over a crust set up that produced a handful of large avalanches during mid to late February.



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 by the increase in easterly wind from Dec 24th till the beginning of March.




Current weather can be found on the  CNFAIC weather page as well as MountainWeather.com’s Alaska page.


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

Observations
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