Avalanche Advisory

Turnagain Area Avalanche Advisory Friday, March 29th 2013 5:29 am by John Fitzgerald ARCHIVED ADVISORY - All advisories expire after 24 hours from the posting date/time.

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The avalanche hazard is MODERATE above treeline, where dense wind slabs up to 18" in depth will be easy for a snowmachine or skier to trigger today.  Below treeline the hazard is LOW and will rise to MODERATE as more snow falls & temperatures warm.  The main concerns below treeline will be shallow loose snow avalanches and isolated pockets of wind slab that will become easier to trigger as the day warms.

Show the Complete North American Avalanche Danger Scale

North American Public Avalanche Danger Scale Avalanche danger is determined by the likelihood, size and distribution of avalanches. Danger Level Travel Advice Likelihood of Avalanches Avalanche Size and Distribution 5 Extreme Avoid all avalanche terrain. Natural and human- triggered avalanches certain. Large to very large avalanches in many areas. 4 High Very dangerous avalanche conditions. Travel in avalanche terrain not recommended. Natural avalanches likely; human- triggered avalanches very likely. Large avalanches in many areas; or very large avalanches in specific areas. 3 Considerable Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential. Natural avalanches possible; human- triggered avalanches likely. Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas. 2 Moderate Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern. Natural avalanches unlikely; human- triggered avalanches possible. Small avalanches in specific areas; or large avalanches in isolated areas. 1 Low Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features. Natural and human- triggered avalanches unlikely. Small avalanches in isolated areas or extreme terrain. Safe backcountry travel requires training and experience. You control your own risk by choosing where, when and how you travel.

2 Moderate Alpine / Above 2,500'

Travel Advice: Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

2 Moderate Treeline / 1,000'-2,500'

Travel Advice: Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

2 Moderate Below Treeline / Below 1,000'

Travel Advice: Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

This Sunday is the 2^nd ANNUAL CORN HARVEST - get it on your calendar now !! Come join the CNFAIC Friends and Forecasting staff on Turnagain Pass for FREE FOOD, games, prizes, etc. This is one way we would like to thank all of you for your dedication and support.

Avalanche Problem 1

Winds over the last 24 hours have been strong enough to move around snow to create sensitive slabs.  Yesterday my partner and I observed these slabs starting to build.  Other parties reported similar conditions along and near ridge crests and on leeward slopes.  These slabs will be most likely to propagate and pick up speed on steep south facing upper elevation starting zones and above cross loaded gullies.  If you notice shooting cracks or the snow below your feet or sled feels hollow and you happen to be in steep terrain, back off before you're moving downhill with the slab.  Warmer temps and continued high winds will help to make these slabs be "upside down" and release with ease.

Avalanche Problem 2

While snowfall amounts have been lower than what was forecasted yesterday, there is still enough loose snow in non wind affected areas to warrant attention.  Volume of these sluffs should be in the low to medium range.  Volume will increase as more snow accumulates through the day.   Sluffs will release more easily as temps climb.  On steep south facing terrain crusts will allow the snow to move more quickly.  These avalanches will be manageable on their own but have the potential to carry people into gullies & trees, and over cliff bands.  Choosing terrain that gives you options for escape will be important in dealing with this problem today.

Additional Concern---Cornice Fall
The winds of the past day have also helped to build the size of cornices.  Steer clear of these behemoths as they can do significant damage.  The largest avalanches that have occurred in the month of March have been the result of cornices dropping.

In the past 24 hours the Turnagain Pass SNOTEL has picked up 6" of new snow with .5" of water.  Winds at the Seattle Ridge weather station at 2,400' have averaged 30mph out of the SE with gusts to 59mph.  Temperatures have averaged 16.5 degrees F at this location.  Temperatures have been on the rise since the early morning hours and are currently in the low 20s F.

Today expect continued intermittent snowfall, with 4-7" of accumulation possible.  Winds at ridge tops will average 35-40mph out of the SE with gusts over 50 mph.  Temperatures at 1,000' will be in the low to mid 30 F range.

The extended outlook calls for a continuation of unsettled weather going into the weekend with snowfall amounts remaining relatively light.
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Kevin will issue the next advisory tomorrow morning, March 30th.

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).

Riding status is not associated with avalanche danger. An area will be open to motorized use in accordance to the Forest Management Plan when snow coverage is adequate to protect underlying vegetation. Backcountry hazards including avalanche hazard are always present regardless of the open status of motorized use areas.

(Updated: May 06, 2018 )

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