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Issued
Fri, December 11th, 2009 - 7:00AM
Expires
Sat, December 12th, 2009 - 7:00AM
Forecaster
CNFAIC Staff
Avalanche risk The Bottom Line

Good morning backcountry travelers this is Carl Skustad with the Chugach National Forest Avalanche Information Center on Friday December 11th 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

All areas designated for snowmachines (except Placer and 20 Mile) on the Chugach National Forest are open. Please remember that Center and Divide Creek near the Johnson Pass Trailhead are always closed due to the current Forest Plan. These areas are periodically patrolled by law enforcement. We are monitoring the snow at Placer and 20 Mile and will open those areas as soon as there is enough snow, these colder temps down low are really helping these areas.

WEATHER ROUNDUP

3800′ -Sunburst Wx Station-

Temps are approaching the 5th day in a row since 2pm 12/6/09 of sustained above freezing temps. Temps have been decreasing slightly, the current temp is 32 deg F. Winds are light 3-11 out of the south.

2600′-Seattle Ridge Wx Station-

Winds are light 2-12 out of the northeast.

1800′-Center Ridge Wx Station-

Precip: 0 inches of water and 0 inches of new snow

minus 2” of total snowpack due to settlement for total depth of 56 inches

Temperature: 21 deg F. Temps have been below freezing the last 24 hours.

Expect foggy conditions again this morning. Above the fog we have sunshine and daydreams. Not even a smudge on the radar. The NWS forecast and models indicate the omega block that has been setting over southcentral will weaken the end of the weekend. We are slowly seeing the inversion weaken as well. Once again expect temperatures close to the freezing mark at ridgetop elevations today and cooler temperatures at lower elevations. Our current temperatures range from 14 deg F at sea level to 32 on top of Sunburst. Summit Lake is the cold spot once again at 3 deg F.

Forecast

WESTERN PRINCE WILLIAM SOUND-

INCLUDING…WHITTIER…SEWARD…GIRDWOOD…MOOSE PASS

INCLUDING…WHITTIER…SEWARD…GIRDWOOD…MOOSE PASS

500 AM AKST FRI DEC 11 2009

.TODAY…MOSTLY SUNNY. AREAS OF FOG INLAND. HIGHS IN THE LOWER

TEENS TO LOWER 20S EXCEPT MID 20S TO LOWER 30S ALONG THE COAST.

VARIABLE WIND 10 MPH EXCEPT NORTH TO WEST WIND 15 TO 25 MPH WITH

LOCAL GUSTS TO 35 MPH NEAR SEWARD AND WHITTIER.

.TONIGHT…MOSTLY CLEAR. PATCHY FOG INLAND. LOWS 5 TO 15 ABOVE

EXCEPT 15 TO 25 ALONG THE COAST. VARIABLE WIND TO 10 MPH EXCEPT

NORTH TO WEST WIND 15 TO 25 MPH WITH GUSTS TO 35 MPH NEAR SEWARD

AND WHITTIER.

.SATURDAY…MOSTLY SUNNY. PATCHY MORNING FOG. HIGHS IN THE 20S

EXCEPT 30 TO 35 ALONG THE COAST. LIGHT WINDS. NEAR SEWARD AND

WHITTIER…NORTH TO WEST WIND 10 TO 20 MPH WITH GUSTS TO 30 MPH

IN THE MORNING.

.SATURDAY NIGHT…PARTLY CLOUDY IN THE EVENING THEN BECOMING

MOSTLY CLOUDY. LOWS 10 TO 25 ABOVE…COLDEST INLAND. VARIABLE

WIND TO 10 MPH. NEAR SEWARD…NORTH WIND 15 MPH.

TEMPERATURE / PRECIPITATION

SEWARD 25 22 27 / 0 0 0

GIRDWOOD 23 20 26 / 0 0 0

AVALANCHE DISCUSSION

Although this is our fifth day with a heavily inverted atmosphere, temps are dropping. Remember that an inversion means cooler air is trapped under warmer air aloft. This is an indication of a very stable atmosphere. Since our avalanche danger is low again today I’ll take the chance to mention a few things we need to remember from this weeks weather. Surface hoar formation from sea level to ~1500 feet. Wind and or melt freeze crusts above 2000 feet. A temperature gradient in the upper 6-8 inches of snow that is most likely forming near surface facets. Lastly, a bomber slab of snow setting on depth hoar (at ground). These will be important factors to remember when we get additional snow fall.

Due to insignificant results in recent snowpits, a lack of recent natural or human-triggered avalanches since Monday around Summit Lake, and a similar weather forecast from the NWS, today’s avalanche danger level will remain LOW. LOW is defined as: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features. Natural and human-triggered avalanches unlikely. Very small avalanches in widespread areas; or small avalanches in isolated areas.

Normal Caution is advised.

Be careful not to discredit sunsluffs near or above your location.

With the very warm inverted air this week we are seeing a temperature gradient in the upper 6-8 inches of snow. Even though the air temperature reached the mid 40’s the low angle of the sun and the long wave radiation from the snowpack kept the surface snow temperatures below freezing. This is why we have not seen wide spread surface snow instability. This is however why we may see near surface faceting and miner sun crusts that will be our next week layer and bed surface.

The secondary concern today are glide cracks. Tincan in particular has lots of these crevasse like features. People and dogs have fallen into these before in the past, and they can be very difficult to crawl out of. Make sure your partner knows where you are around these glide cracks.

Always remember that safe backcountry travel requires training and experience. You control your own risk by choosing where, when, and how you travel. Follow your time tested backcounry rituals. One at a time, watch your partner and be prepared.

This concludes today’ advisory. The next advisory will be tomorrow morning at 7 am. Thanks and have a sun capped foggy day.

Fri, December 11th, 2009
Alpine
Above 2,500'
0 - No Rating
Avalanche risk
Treeline
1,000'-2,500'
0 - No Rating
Avalanche risk
Below Treeline
Below 1,000'
0 - No Rating
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.