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Issued
Thu, March 1st, 2012 - 7:00AM
Expires
Fri, March 2nd, 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, March 1st 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 will rise to CONSIDERABLE today for storm snow instabilities with new snow and wind arriving currently. Wind slab avalanches will be the most dangerous problem today and these will likely to be triggered by a person on slopes steeper than 35 degrees with recent wind deposited snow. In areas out of the wind below treeline, a MODERATE danger exists for loose snow avalanches on the steeper slopes.

AVALANCHE DISCUSSION

Calm weather at most locations yesterday allowed for anCNFAIC Staff good day of riding on Sunday/Monday’s soft settled powder. Easterly winds, ahead of today’s storm, did pick up slightly on the upper ridgelines and in some locations were able to transport snow into soft sensitive wind slabs; foreshadowing today’s wind slab problem. We ran into one of these very touchy slabs yesterday on the southern end of Turnagain Pass. Hence, winds will be the big player in increasing the avalanche danger for today.

Primary concern:

Wind slab avalanches. Though we have only 4-8″ of snow on tap, there is 12-18″ of light powder sitting on the surface that is just waiting for a bit of wind to blow it around. This large source of “available snow for transport” will allow for slabs to form that could be quite deep in certain areas and unmanageable. Adding to this, the winds are expected to average around 35-45mph – right in the “optimal range” for wind slab formation.

These fresh wind slabs are likely to be quite sensitive as they are sitting on loose weak snow. Steering clear of wind drifted areas (e.g., stiff and hollow feeling snow) as well as areas where cracks shoot out from you snowmachine, board or skis is advised. Also, keep in mind Cornices continue to grow and teeter on the brink of failure.

Secondary concern:

In areas without wind effect, loose snow avalanches, or sluffs, are expected to be easy to initiate with the continued new light snow over the existing loose snow on the surface. These continue to have the potential to run fairly quickly and far and will be able to entrain a lot of snow.

Last, we have seen a sun crust that formed two days ago. It seems to be scattered along southerly aspects and not widespread. However, this can provide a good bed surface for an avalanche initiated in these areas to run further and faster than expected.

MOUNTAIN WEATHER

It was anCNFAIC Staff mostly calm, but somewhat cloudy, day in the backcounty. Low clouds inhibited visibility but a few windows did open up. Easterly winds were light with moderate gusts to 15-20mph on the exposed ridges. Light snow added anCNFAIC Staff 1-2″ in many places and temperatures were in the upper teens near treeline.

Today we have a front marching in from the southeast associated with a low pressure system spinning over the Aleutian Islands. Strong easterly winds averaging around 35-45mph with gusts over 50mph are expected. Light snow is falling currently and should increase through the day with 4-8″ of accumulation expected – possibly more above treeline. Temperatures look to be in the teens at the mid and upper elevations and in the mid to upper 20’s in the lower elevations. Snowfall and winds are likely to decrease tonight but light snow should continue into tomorrow.

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, March 1st, 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.