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ARCHIVED - Forecasts expire after 24 hours.
Issued
Wed, April 25th, 2012 - 7:00AM
Expires
Thu, April 26th, 2012 - 7:00AM
Forecaster
Graham Predeger
Avalanche risk The Bottom Line

Good morning. This is Graham Predeger with the Chugach National Forest Avalanche Information Center on Wednesday, April 25th at 7am. This will serve as 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).

ANNOUNCEMENTS

The next advisory will be issued Saturday morning. Keep checking the photos/observations page for up to date information.

A big THANK YOU to everyone who showed up or stopped by Turnagain Pass last Sunday for the First Annual Corn Harvest Event, sponsored by the Friends of the CNFAIC!

BOTTOM LINE

A MODERATE avalanche danger exists this morning within the core advisory area where wet loose and wet slab avalanches are the primary concern as slopes as high as 3500′ did not freeze overnight, or may have froze superficially. Later in the day, slopes at all elevations will continue to heat up and the danger may rise to CONSIDERABLE with natural avalanche activity moving up the spectrum from unlikely to possible. Avoid steep, rotten slopes where the snow cannot support your weight. Furthermore, limit time spent under glide cracks and cornices that have yet to release as these are ticking time bombs.

AVALANCHE DISCUSSION

A drive through Turnagain pass and one is able to see the extent of avalanche activity over the past week. Naturally occurring wet loose, wet slab, glide avalanches, glide cracks and even a couple dry slab avalanches have been observed since last Wednesday. Most of this activity is from 4-7 days ago and activity has slowed substantially since late last week as our snowpack continues its transition toward summer. However, new glide cracks are continuing to open up on south and east facing slopes in the Girdwood Valley and Turnagain pass areas.

Primary Concern – Wet Avalanches and Glide Avalanches

Wet avalanches will become more of a concern later in the afternoon/ evening as the sun breaks down bonds between individual snow grains. Before this happens, there is decent corn snow to be found, though timing is everything. Once a slope cannot support your weight (off your skis or snowmachine) and you are sinking past your boot tops, retreat. This is a good indicator that a slope is becoming dangerously unstable due to rapid warming.

Glide avalanches continue to pose a threat at all times during the day. Unpredictable by nature as to when a glide crack may release, the good news is that we know where they will release. If you see a glide crack (and there are many) limit your time spent underneath these. Do not high-mark under glide cracks, do not set your skin track under glide cracks, do not eat your lunch under glide cracks and you will not be in danger of getting hit by one of these ticking time bombs.

Cornices

As with glide cracks, avoid time spent below these behemoths, giving cornices an extra wide berth when travelling on ridges where cornices have built up over the season. These are particularly large this late in the season and prove to be very touchy as we progress into spring.

Persistent Slabs – Above tree line

There is an older layer of buried surface hoar from March that is still proving reactive in isolated areas above tree line. I observed a fresh slab that released in the last couple days just lookers right of the Squirrel Flats up-track. Buried surface hoar was likely the culprit in this wide, low angle avalanche. Though few and far between now, be aware that buried weak layers do still exist on higher elevation slopes with a northerly tilt.

MOUNTAIN WEATHER

The Jetstream continues to flow far south of mainland Alaska keeping any exciting weather at bay for the next few days. The big melt continues this week with daytime temperatures reaching into the 50’s at 1000 feet and light winds from the northeast in the 3-17mph realm. Overnight, sea level temps dipped to 25 degrees in the eastern Turnagain arm area, though many mountain top areas struggled to break below the 32 degree mark (freezing).

Mostly clear skies will dominate our region over the next several days with a slight chance of isolated rain or snow as we head into the weekend.

CNFAIC Weather Page and the NWS forecast

Wendy will issue the next advisory Saturday morning. If you get out in the backcountry we want to know what you are seeing. Please send us your observations using the button at the top of this page or give us a call at 754-2369. Thanks and have a great day.

Wed, April 25th, 2012
Alpine
Above 2,500'
2 - Moderate
Avalanche risk
Treeline
1,000'-2,500'
2 - Moderate
Avalanche risk
Below Treeline
Below 1,000'
2 - Moderate
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.
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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.