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Issued
Thu, March 3rd, 2011 - 7:00AM
Expires
Fri, March 4th, 2011 - 7:00AM
Forecaster
Kevin Wright
Avalanche risk The Bottom Line

Good morning backcountry travelers this is Kevin Wright with the Chugach National Forest Avalanche Information Center on Thursday, March 3rd 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

Today’s avalanche danger rating is Low with pockets of MODERATE. Wind slab from last weekend could still react to the right trigger. The more dangerous but less likely danger is triggering a deep slab, which still lingers in the shallow areas of the Kenai and Turnagain arm.

AVALANCHE DISCUSSION

The last few days have been calm and uneventful. Surface conditions are not very enticing for skiers or riders right now, keeping the number of avalanche triggers and observers to a minimum. A couple of avalanche concerns remain.

Old lingering wind slab is the primary concern today. The wind events of Saturday and Sunday produced a few notable avalanches, both natural and human triggered. The possibility of triggering a wind slab is confined to steeper areas near ridges or convex rolls on a lee aspect. See photo for example of a recent avalanche on a convex roll:

The deeper weak layers remain a concern through the region. Snow pit results in some areas are showing high strength (difficult to initiate), but a weak layer that may collapse catastrophically when it fails. This indicates a low likelihood of triggering but a larger resulting avalanche if it does. The hazard for this type increases as you move towards shallower areas at the Southern end of Turnagain Pass.

This photo from last week is a good example of the worst case scenario. It happened sometime during the wind storm.

The easiest way to define the pockets of heightened hazard is to gauge the snowpack depth. Deep, wide open, planar slopes in Turnagain Pass seem to have the safest combination of variables. Steep, rocky, shallow, unsupported terrain with recent wind loading is the most likely place to trigger an avalanche.

The big question that’s hard to answer right now is, “where is the snow unstable?” The nemesis of spatial variability is our problem. It’s worth spending some extra thought when deciding where you ski or ride to avoid those pockets of instability.

WEATHER ROUNDUP

The weather pattern is fairly stable right now. There has been no significant snowfall in 10 days. The last major wind event was last weekend. Currently temperatures are dropping to single digits at night and getting into the 20s during the day. Wind overnight was moderate with some higher gusts in Grandview and Girdwood. Clear skies are expected today with light to moderate wind and temperatures in the 20s.

ANNOUNCEMENTS An APU student is conducting a survey on backcountry skiing group dynamics. Click on the link to participate in research on avalanche safety. Click here to take survey

The Forest Service is installing winter use bridges across Granite creek in Turnagain Pass. Be aware of an ice road from the Lyon creek bridge south towards Johnson Pass on the West side of the highway. Heavy equipment will also be used in the area.

I will issue the next advisory tomorrow morning at 7am. If you get out in the backcountry give us a call at 754-2369 or send us your observations using the button at the top of this page. Thanks and have a great day.

The NWS weather forecast for:

WESTERN PRINCE WILLIAM SOUND-

INCLUDING…WHITTIER…SEWARD…GIRDWOOD…MOOSE PASS

500 AM AKST THU MAR 3 2011

.TODAY…SUNNY IN THE MORNING…THEN PARTLY CLOUDY WITH A SLIGHT

CHANCE OF SNOW SHOWERS ALONG THE GULF COAST IN THE AFTERNOON.

HIGHS 15 TO 25. VARIABLE WIND 10 MPH. NEAR SEWARD…NORTH WIND

15 TO 30 MPH. NEAR WHITTIER…WEST WIND 15 TO 30 MPH BECOMING

LIGHT IN THE AFTERNOON.

.TONIGHT…PARTLY CLOUDY. A SLIGHT CHANCE OF SNOW SHOWERS ALONG

THE GULF COAST IN THE EVENING. LOWS 5 BELOW TO 10 ABOVE EXCEPT

IN THE TEENS ALONG THE COAST. LIGHT WINDS EXCEPT NORTH WIND

15 TO 25 MPH NEAR SEWARD.

.FRIDAY…PARTLY CLOUDY IN THE MORNING THEN BECOMING MOSTLY SUNNY.

HIGHS IN THE 20S. LIGHT WINDS EXCEPT NORTH WIND 10 TO 20 MPH

NEAR SEWARD.

.FRIDAY NIGHT…CLEAR. LOWS ZERO TO 15 ABOVE. LIGHT WINDS

EXCEPT NORTH WIND 10 TO 20 MPH NEAR SEWARD.

.SATURDAY…MOSTLY SUNNY. HIGHS IN THE LOWER 20S TO LOWER 30S.

LIGHT WINDS EXCEPT NORTH WIND 10 TO 20 MPH NEAR SEWARD.

.SATURDAY NIGHT…PARTLY CLOUDY. LOWS ZERO TO 10 ABOVE.

.SUNDAY AND SUNDAY NIGHT…MOSTLY CLEAR. HIGHS IN THE 30S.

LOWS ZERO TO 15 ABOVE.

TEMPERATURE / PRECIPITATION

SEWARD 26 17 28 / 20 20 0

GIRDWOOD 18 2 18 / 0 0 0

WEATHER STATION SUMMARY for Turnagain Pass:

-3800′ Sunburst Wx Station-

Temperature 8 degrees. Wind gusting to 27 from the NE.

-2600′ Seattle Ridge Wx Station-

Temperature 11 degrees. Light wind from the SE. Gusts to 19 overnight.

-1800′ Center Ridge Wx Station-

Temperature 13 degrees. No new snow recorded.

Thu, March 3rd, 2011
Alpine
Above 2,500'
1 - Low
Avalanche risk
Treeline
1,000'-2,500'
1 - Low
Avalanche risk
Below Treeline
Below 1,000'
1 - Low
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. Dangerous avalanche conditions. 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.