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Issued
Wed, April 11th, 2012 - 7:00AM
Expires
Thu, April 12th, 2012 - 7:00AM
Forecaster
Wendy Wagner
Avalanche risk The Bottom Line

Good morning. This is Wendy Wagner with the Chugach National Forest Avalanche Information Center on Wednesday, April 11th 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).

ANNOUNCEMNTS

This will be our final week of daily avalanche advisories, ending April 15th. We will be issuing one mid-week update on Wednesday and one weekend update on Saturday mornings through April 30th. Observations from our staff/public will be kept current and checking the photos/observations page regularly will be the best place to find up to date information for the last two weeks of April.

BOTTOM LINE

The danger remains at MODERATE for two specific concerns. First, wet avalanches will be possible to trigger today on east, south and west aspects at all elevations as daytime heating is expected to break down last night’s shallow refreeze due to significantly warmer overnight temperatures. Second, slab avalanches continue to be possible to trigger on northerly slopes above 2000′ where buried surface hoar exists 10-20″ deep.

AVALANCHE DISCUSSION

For those reading this advisory daily, the message today remains similar to that of the past week. People continue to find and trigger slab avalanches in, and around, our forecast zone. Yesterday, a skier triggered a slab around 150′ wide and around 18″ deep on a north facing aspect above treeline in the Lynx creek area. These are all failing on a layer of buried surface hoar that sits between 1 and 2 feet deep. As far as wet avalanches yesterday, no new slides were seen/reported. This is likely because the increase in winds, with a solid overnight refreeze, managed to keep the southerly aspects from breaking down.

Primary Concern – Wet Avalanches, Glide Avalanches and Cornices

Warm overnight temperatures (above freezing at the mid elevations) has limited a good refreezing of the snow surface. This will give daytime heating and solar radiation a much easier time breaking down surface crusts and warming the snow to the point human triggered wet avalanches are possible. Watching out for slopes with boot deep, or deeper, saturated snow is the best way to avoid a wet slide. Even a small wet sluff can become very dangerous and difficult to get out of.

Glide avalanches have been releasing during the past few days. A reminder that before sitting down to eat lunch, look up to make sure one of these opening brown cracks is not above you.

Cornices deserve respect. They continue to pull away from the ridgelines with our warm temperatures forming ‘cornice crevasses’ as well as becoming sensitive to the weight of a person.

Secondary Concern – Persistent Slabs

The term persistent slab fits perfectly with our 2 week old layer of buried surface hoar that continues to be, well…persistent. The best place to find and trigger an avalanche on this layer will be any slope that has not avalanched already and is sporting dry snow, specifically slopes with a northerly aspect or tilt above 2000′. For anyone committing to ski or ride in these areas, having an exit strategy in the case the slope slides is very wise. Additionally, triggering a slab in terrain with high consequences, e.g., slopes above cliffs, a small ride could become very serious very quick.

MOUNTAIN WEATHER

It was yet anCNFAIC Staff beautiful sunny day in the backcountry yesterday; though a bit breezy on the peaks. East winds picked up for the course of the day at the higher elevations blowing 15-20mph and gusting to 30mph. Temperatures climbed into the upper 20’s on the ridetops and the mid 30’s near treeline.

Overnight, a warm air mass along with cloud cover has been streaming in from the east keeping temperatures up. Above treeline alpine areas are the warmest this morning, in the low to mid 30’s, while below treeline sits right around 30F. These numbers should increase today with partly sunny skies into the upper 30’s above treeline and low 40’s below. East winds have decreased to 5-10mph with gusts near 15mph where they are expected to stay. No precipitation is expected for the next few days as the high pressure over us is forecast to remain.

CNFAIC Weather Page and the NWS forecast

Chris will issue the next advisory tomorrow 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 11th, 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.