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ARCHIVED - Forecasts expire after 24 hours.
Issued
Wed, April 14th, 2010 - 7:00AM
Expires
Thu, April 15th, 2010 - 7:00AM
Forecaster
CNFAIC Staff
Avalanche risk The Bottom Line

Good morning backcountry travelers this is Matt Murphy with the Chugach National Forest Avalanche Information Center on Wednesday April 14th, 2010 at 7 am. 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).

ANNOUNCEMENTS

Skookum Valley and Skookum Glacier are closed to motorized vehicles (snowmachines, helicopters, ATVs) except for subsistence uses.. This closure is directed in the current Chugach National Forest Land and Resource Management Plan. Placer River Drainage remains open for motorized use to Spencer Glacier.

WEATHER ROUNDUP

-The winds are moderate this morning averaging 16-21mph with some strong gusts up to 31mph down on Seattle Ridge

-The 24 hour snotel sites are reporting:

-0.1 inches of water, 4” of melting/settlement at 1800′ at Turnagain Pass

-0.1 inches of water, 3” of melting/settlement 1100′ at Grandview

-0.1 inches of water, 2” of melting/settlement at 1400′ at Summit Creek.

-This morning’s (5am) radars are full of precip with the majority missing our location and heading east of Cordova

-Temps are starting off about the same this morning at most weather stations as they did yesterday morning. Above freezing temps made it up to 33 degrees at 2600′ yesterday. This morning’s temperature range is 33 degrees F at sea-level and 22 degrees F at 3800′.

AVALANCHE DISCUSSION

Today’s avalanche danger is LOW with pockets of MODERATE. Small human-triggered avalanches will be possible on isolated wind slabs sitting on top of a crust with buried surface hoar/facets on top of that crust.

Surface hoar was observed on Tincan, Pastoral, Twin Peaks, and Pete’s North, and Cornbiscuit at the end of last week. On Sunday we found this surface hoar buried and standing up on a small wind lip on Tincan. This small pocket was very reactive to human triggers. Monday, we tried to confirm this same layer of buried surface hoar on Sunburst, but could not find it. We did, however, find facets on top of the most recent sun crust instead of the surface hoar. Recent observations have described this surface hoar as large above 3200′ (up to 1cm).

Yesterday’s sun pre-cooked a lot of the surface snow. We observed lots of small point release avalanches on sun affected slopes. Only a couple of spots entrained enough snow to become medium sized avalanches. Some new glide crack avalanches were reported in Placer Valley.

The sun is the critical “watch out” situation this time of year. April sun and temps can change the snowpack much more drastically than January or February sun. Avalanche danger can increase quickly during periods of rapidly warming temps and direct sunlight; especially, when the sun hits fresh snow.

Glide cracks are secondary concern today. These crevasse like features are those cracks that go all the way to the ground. Avoid traveling underneath these cracks. Glide cracks and full depth release avalanches have been occurring on warm sunny days. We are seeing more and more of these glide cracks form everyday.

WEATHER FORECAST (National Weather Service)

WESTERN PRINCE WILLIAM SOUND-

INCLUDING…WHITTIER…SEWARD…GIRDWOOD…MOOSE PASS

500 AM AKDT WED APR 14 2010

.TODAY…SNOW AND RAIN. SNOW ACCUMULATION 1 TO 4 INCHES. HIGHS IN THE

30S TO NEAR 40. SOUTH TO EAST WINDS 10 T0 20 MPH.

.TONIGHT…SNOW IN THE EVENING…THEN A CHANCE OF SNOW SHOWERS AFTER

MIDNIGHT. SNOW ACCUMULATION UP TO 1 INCH. LOWS IN THE LOWER 20S TO

LOWER 30S. LIGHT WINDS EXCEPT SOUTH 15 MPH NEAR SEWARD IN THE

EVENING.

.THURSDAY…SKIES BECOMING PARTLY CLOUDY. A CHANCE OF SNOW SHOWERS IN

THE MORNING. HIGHS AROUND 40. LIGHT WINDS EXCEPT WEST 10 TO 15 MPH

NEAR WHITTIER.

TEMPERATURE / PRECIPITATION

SEWARD 41 28 42 / 100 70 0

GIRDWOOD 40 26 40 / 100 90 20

Short Term Weather Model Forecasts (NAM, WRF, GFS) for the Kenai Mountains near Turnagain Pass

Sea-level: temps are forecasted between 26-40 and between 0.1-0.25” of water forecasted

3000′: temps are forecasted in the range of 23-32 degrees F with winds 5-10 mph

6000′: temps are forecasted in the range of 14-23 degrees F with winds 5-10 mph

WEATHER STATION SUMMARY for last 24 hours at TURNAGAIN PASS

3800′-Sunburst Wx Station

Temp (5am): 22 (same as yesterday morning)

Winds: In last 24 hours winds have been light-moderate averaging 6-20mph with a strong max gust of 37mph

HIGH TEMP of 29 at 1pm

2600′-Seattle Ridge Wx Station

Temp (5am): 25 (same as yesterday morning)

Winds: In last 24 hours have been light to moderate averaging 5-21 mph with a strong max gust of 31mph

HIGH TEMP of 33 between 4-5pm

1800′-Center Ridge Wx Station

Temp (5am): 29 (1 degrees warmer than yesterday morning)

Precip: 0.1 inches of water, 4 inches melting/settlement

HIGH TEMP 43 between 4-6pm

Thanks for checking today’s avalanche advisory. The next one will be posted tomorrow Thursday April 15th, 2010.

Wed, April 14th, 2010
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. 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.
Observations
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04/16/24 Turnagain Observation: Cornbiscuit
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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.