Avalanche Advisory

Turnagain Area Avalanche Advisory Wednesday, December 16th 2015 7:00 am by Heather Thamm ARCHIVED ADVISORY - All advisories expire after 24 hours from the posting date/time.

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Today the avalanche danger is MODERATE where loose snow avalanches and tender wind slabs could have high consequences on steep and exposed terrain features.  Wind slabs 8-10" thick will be more likely in the Alpine where poor visibility could make assessing the conditions difficult today.  Assess changing surface conditions and be on the look out for loading snow and shooting cracks.

Ice climbers: Snowfall totals in Portage Valley have been verified at 12” or more on Monday and another 3-5" fell yesterday.  This is potentially more than a “moderate” avalanche problem for this user group given the extreme and complex nature of the terrain.  

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.

Fireside Chat #3 – Human factors and decision-making on Thursday, Dec 17th!! Join our newest CNFAIC forecaster, Aleph Johnston-Bloom Thursday night from 6:30-8:00pm in Girdwood at the Glacier Ranger Station (Forest Service office) for an introduction to what avalanche professionals and psychologists refer to as the “human factor” as it relates to decision-making in the backcountry

CNFAIC is hosting a Free Avalanche Rescue Workshop on Sunday, December 20^th at Turnagain Pass. This is a great opportunity to practice beacon searches, learn strategic shoveling techniques and meet local forecasters! This workshop is open to everyone and anyone, novices and experts.

More areas are open for over snow vehicles on the Seward Ranger District!  Please see updated table at the bottom of this page.

Avalanche Problem 1

Yesterday snowfall was concentrated near Turnigain Arm favoring the Northern side Turnagain Pass and Portage Valley with a total of 3-5” of new snow. Moderate ridgetop winds flipped from the Northeast to a Westerly direction for several hours during the most intense burst of snow flurries. Today another small shot of snow is expected along with moderate winds from the Northeast. Loose snow avalanches and tender wind slabs up to 8-10” thick are possible on steep convex terrain features and just below ridgelines, on all aspects.  This unstable snow could have high consequences if triggered on exposed terrain features like cliffs, gullies, and large open slopes.

A total of 2-3’ of new snow has fallen since last Wednesday and has left a mostly right side up snow pack. Many layers of new snow exist as a result of incremental loading and moderate winds in the upper elevations. Visibility is expected to be limited today, but if a window opens up, assess snow conditions carefully at higher elevations. 

Snow flurries intensified yesterday in the early afternoon making visibility difficult at Sunburst. 

We have been actively tracking several layers of weak snow buried under 2-3’ of new snow over the past week. Data collected over the last 3 days (including heavy impact from motorized slope testers) is pointing towards good stability. Right now this problem is becoming an outlier, but we will continue to monitor these layers with any additional loading or stress to the snowpack. 

Yesterday snow showers intensified for several hours as a cold front left 3-5” of snow in the upper elevations of Turnagain Pass and Portage Valley. Ridgetop winds were moderate from the Northeast, switching to a Westerly pattern in the afternoon through late evening. Temps were cool, high teens F in the alpine, and high 20F's at sea level. Overnight winds were light from the Northeast.

Today expect more showery conditions with another 3-5” of new snow in upper elevations. Easterly ridgetop winds will increase to 15-30mph this morning and remain moderate into the evening.

Tomorrow more snow showers are anticipated. Temps are expected to increase to freezing 32F at sea level causing mixed rain and snow. Winds are expected to be light to moderate from the East. 

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

RIDGETOP 24-hour data (6am - 6am)

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: Apr 15, 2019 )

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