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Issued
Sun, November 27th, 2011 - 7:00AM
Expires
Mon, November 28th, 2011 - 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, November 27th 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 is MODERATE for fresh wind slab avalanches on leeward slopes. Human triggered avalanches will be possible today in areas with recent wind deposited snow. These are most likely to be found above treeline, off ridgelines and on rollovers. Below treeline, and out of the wind, the danger is generally LOW.

AVALANCHE DISCUSSION

Yesterday, 3 human triggered avalanches were reported in the Turnagain Pass area, both on the east and west side of the road. Details are limited, but it seems these were all confined to the new snow that has accumulated to 8-12+” during the past week.

Today, the primary concern will be fresh wind slabs forming due to the recent increase in wind. Though winds are moderate, currently in the 20’s, and expected to increase slightly into the 30’s, there is ample light snow to be blown around. Soft, sensitive wind pockets could be triggered in steeper leeward terrain today. Watch for any cracking in the snow from your sled, board or skis. This is a bull’s eye clue that a slab could pop and the slope could slide. Areas most likely to trigger a wind slab are on and off ridgelines and on the steepest point of a rollover/convexity.

Snowpack

To date, our snowpack has been relatively stable; however, it does have a poor structure. In general, there exists weak faceted snow sitting under a wind slab, varying from 0-12+” thick, with 8-12” of loose, new snow on top. With additional weight from new snow, or wind deposited snow, the weak faceted layer has potential to fail. In this case, larger and more unmanageable slides are possible. We are keeping this in mind as the winds pick up today and significant snowfall is expected this week.

MOUNTAIN WEATHER

Mid-level clouds yesterday allowed for sunny skies above treeline and cloudy skies below. Temperatures were around 10F while winds were light and variable. Overnight, winds picked up from the east and are currently gusting around 20mph. Today, patches of clear sky will begin to fill in with high clouds and light snow showers as a system moves in from the east. There is a chance for a few inches to fall by the evening, with several more accumulating into Monday. Winds are forecast to increase, gusting into the 30’s from the east, and temperatures will increase as well, rising into the mid and upper-teens today.

It looks as though a change in our colder than average weather pattern is approaching. Early next week, a large low pressure system is forecast to head into the Gulf, bringing warmer and wetter conditions.

CNFAIC Weather Page and the NWS forecast

I will issue the next advisory tomorrow morning at 7am. 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, November 27th, 2011
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.