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Issued
Sun, February 5th, 2012 - 7:00AM
Expires
Mon, February 6th, 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 Sunday, February 5th 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).

BOTTOM LINE

The avalanche danger remains CONSIDERABLE for two main concerns. First, wet avalanches are likely at lower elevations where light rain is forecast to fall on snow; these can be much larger and dangerous than expected due to buried surface hoar existing in some areas. Second, wind slab avalanches will be likely to trigger at the mid and upper elevations where strong winds will continue to load leeward slopes. Conservative route finding and steering clear of lower elevation slopes becoming damp will be prudent.

AVALANCHE DISCUSSION

A break in weather yesterday allowed for a good view of the aftermath from the natural avalanche cycle occurring Wednesday through Friday. Check the many recent observations for more details. A few notable slides were believed to be from Friday, which are a bit ‘ugly’ – meaning they propagated laterally, ran full path and have debris piles you would not want to mess with. CNFAIC Staff concerns are reports from avalanches in the lower elevations of Placer Valley, likely breaking on buried surface hoar, which means they can be triggered from below.

Warm, Windy and Wet conditions will be a game changer for the snow today. This will give the cold light powder a shock with temperatures above freezing below 1000′ and near 30 degrees F above. Light rain and snow later today will add to the shock. Areas with loose snow should see the stability decrease with the new snow becoming wet and inverted (heavier, denser snow on top of lighter snow below) – perfect for wet and soft slab avalanche potential.

Primary concerns for today:

Wet avalanches and soft slab avalanches-

These will be formed mainly by the increase in temperature and light rain on snow at lower elevations. These can be triggered by a person and could be very dangerous in any lower drainage where a buried weakness exists.

Wind slabs and cornice falls-

An increase in southeast winds will continue to load leeward slopes. Yesterday, several people were able to trigger these fresh wind slabs and today should be similar. Slabs that form today could be overlying light snow and will be more sensitive in this case.

MOUNTAIN WEATHER

The sun made a welcome appearance yesterday along with colder temperatures in the single digits to the teens. Riding conditions were quite nice out of the wind. But, it was the wind that wreaked some havoc on the 2′ of light powder. Easterly winds blew in the high teens with 30-40mph gusts, enough for the low density snow to be carried in plumes all day. Clouds have moved in overnight, winds have remained strong at the ridgetop stations and warm air is streaming in.

Today is looking like a warm, windy and wet day as southerly flow is ushering in warm air from the lower latitudes. Temperatures are on the rise – the Turnagain SNOTEL site has jumped from 17F at 9pm to 29 at 6am and should warm anCNFAIC Staff 3 degrees today. Light rain should start falling mid-day below 500′ and wet snow above. It looks like we will get around .4″ of water equivalent by tonight (~2-5″ of snow where it is not raining). Temperatures will be above 32F below 1000′ and decrease to the mid 20’s at 4000′. Southeast winds will be strong, in the 40-50mph range, on the ridge tops.

CNFAIC Weather Page and the NWS forecast

I will issue the next advisory Monday 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.

Sun, February 5th, 2012
Alpine
Above 2,500'
3 - Considerable
Avalanche risk
Treeline
1,000'-2,500'
3 - Considerable
Avalanche risk
Below Treeline
Below 1,000'
3 - Considerable
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.