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ARCHIVED - Forecasts expire after 24 hours.
Issued
Thu, March 29th, 2012 - 7:00AM
Expires
Fri, March 30th, 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 29th 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

Pockets of CONSIDERABLE danger exist above treeline for wind slab avalanches. These are most likely found on West, South and Northerly aspects where slabs formed during the past 24-48 hours may be sitting on buried surface hoar. Pockets of CONSIDERABLE danger also exist at the lower elevations for wet avalanche activity due warm temperatures and rain on snow. CNFAIC Staffwise, there is generally a MODERATE danger for the Turnagain Pass area.

AVALANCHE DISCUSSION

After quite the remarkable cold winter, which has kept excellent dry snow to sea level, it seems the imminent spring warm-up is upon us. Warm temperatures and rain the past two days are wilting our below treeline snowpack and wet saturated snow exists below 2000′ while dry snow remains above treeline. Yesterday’s avalanche activity was relegated to minor wet loose slides below treeline with fresh wind slabs forming above.

Below treeline – Wet Avalanches

With rain on snow below 1000′ and wet saturated snow below 2000′, wet avalanche activity will be a concern for those traveling in the lower elevations. Wet point release avalanches on all aspects (not just southerly as we have been seeing with sun effect) are possible to release on their own today. These have the potential to entrain a lot of wet snow as well as a chance for triggered a deeper slab where buried weaknesses exist.

Above treeline – Wind Slab

The strong to moderate winds during the last 48 hours have been loading slopes near and above treeline. Yesterday, we found that not all, but some, of these recent slabs are sitting on surface hoar in highly traveled locations, making for a touchy wind slab problem for those venturing out of the wet snow to the upper elevations. Careful evaluation of the upper pack is necessary above treeline, as triggering a stiff wind slab could break above or adjacent to you, taking you for a ride.

Cornices and Glide Avalanches

With the warm temperatures, watch for cornices to loosen up and begin pulling away from the ground forming larger ‘cornice crevasses’ or break off all together. Additionally, staying out from under opening glide cracks is advised as many of these are beginning to open up; one did just release south of Devil’s Pass (south of Summit Lake).

Persistent Slab

The two old buried weaknesses (surface hoar and facets around sun crusts buried 3/15) still reside 2-3′ deep in some areas. Though we have not seen an avalanche break into these deeper layers for several days, with the warm temperatures they could become reactive again and warrant mention.

MOUNTAIN WEATHER

After a warm, wet and windy morning yesterday, skies broke up by mid-day and temperatures rose into the upper 40’sF at 2000′ and 30’s on the ridgetops. The rain/snow line has crept up and is hovering just above 1000′ currently. Above treeline, snow that fell Tuesday through Wednesday accumulated to a whopping 15″ in the Girdwood Valley and only 3-5″ on Turnagain Pass. Winds the past 24 hours have been strong from the east on the ridgetops, sustained in the 25-35mph range and gusting in the 40’s and 50’s.

Today, the scattered light rain/snow that is falling this morning may add anCNFAIC Staff few inches of snow up high but diminish with breaking skies possibly later in the day. Temperatures that dropped slightly overnight should rise again into the 40’s below treeline and 30’s above. Easterly winds are forecast to continue but decrease a touch, sustained between 15-20mph with gusts between 35-40mph.

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 29th, 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.