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Issued
Thu, February 16th, 2012 - 7:00AM
Expires
Fri, February 17th, 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 Thursday, February 16th 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

There is a CONSIDERABLE avalanche danger today for wind slab avalanches on all slopes with recent wind deposited snow. These are likely to be dangerous and unmanageable if triggered. High winds with snowfall yesterday, as well as an expected increase in wind later today, will keep human triggered wind slabs likely. The avalanche danger is expected to rise tonight with the approach of anCNFAIC Staff storm.

AVALANCHE DISCUSSION

After the excitement of a mostly clear day on Tuesday to view the avalanche activity after Monday’s storm, we are again shrouded in clouds today as to the extent of the natural avalanches produced from yesterday’s high winds and 10-20″ of new snow. The one exception was a bit of blue sky that poked through in the Summit Lake area where a few recent natural wind slab avalanches were seen.

Primary concern:

Wind slab avalanches that formed yesterday, as well as fresh slabs forming today, will be the primary concern. All slopes that show signs of wind loading (rounded, smooth, rippled and pillow looking surfaces) are very suspect to slide. These slabs are stiff in many areas which can lure a person onto them and release above you. Steering clear of all wind loaded slopes above 35degrees today will be prudent.

Secondary concerns:

Soft slab avalanches and sluffs within the storm snow from both Monday and Wednesday will still be possible as the new snow is currently adjusting to continual loading. These will be found in areas where the snow has been minimally wind affected, most likely below treeline on the steeper rollovers.

Low elevation concerns:

For those traveling in the lower elevations (for example, Placer Valley), there have been a few disconcerting avalanches seen that are suspect to have released on buried surface hoar. Keeping a keen eye out for recent avalanches and avoiding travel under steep slopes on valley bottoms is advised as this kind of avalanche can break above you.

A reminder, Alaska DOT crews have been working non-stop removing the copious snow at Turnagain Pass and parking lots may still be in the process of being cleared. Remember to give the snow removal crews time, and space, to get these lots cleared.

MOUNTAIN WEATHER

Yesterday, just one more storm rolled through our neighborhood since the warmer/wet and windy pattern moved in on February 1st (check out the weather chart for the first half of February). In fact, it marked roughly the 7th system in the past 15 days, with anCNFAIC Staff on tap tonight – and yet anCNFAIC Staff this weekend. Easterly winds that have been raking the region, did so yet again yesterday with averages between 45 and 60mph and gusts over 90mph. The snow/rain line began at sea level and moved up to around 200′ by the evening.

Estimated storm totals for yesterday-

Turnagain Pass: 14-20″ snow (1″ water equivalent)

Girdwood Valley: 10-12″ (.8″ water equivalent)

Summit Lake: 2-4″ (.2″ water equivalent)

A brief break between storms last night will continue through mid-day with cloudy skies, intermittent snow showers (adding 2-4″) and east ridgetop winds ~20-30mph. Late this afternoon, the next system’s front moves in. Expect the east ridgetop winds to ramp up to around 50-60 mph and snowfall to increase, adding around 6-12″ tonight. Temperatures that dropped overnight to around 30F at sea level and 20F at 4000′ should increase to the mid 30’s and mid 20’s respectively today. The rain/snow line with this system looks to be right around sea level.

CNFAIC Weather Page and the NWS forecast

Kevin will issue the next advisory Friday 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.

Thu, February 16th, 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.