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ARCHIVED - Forecasts expire after 24 hours.
Issued
Thu, November 25th, 2010 - 7:00AM
Expires
Fri, November 26th, 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 Thursday, November 25th 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).

ANNOUNCEMENTS

Turnagain Pass and Johnson Pass North Trail Head motorized use areas are open for snowmobile use. Adequate snow is present to prevent resource damage. These areas consist of the lands on the west side of the Seward Highway between the Turnagain Arm and Sixmile Creek and the drainage Southwest of Bench Creek adjacent to the Johnson Pass North Trailhead south to Bench Lake. Center and Divide Creek Drainages are closed to snowmachine use.

All CNFAIC Staff areas of the Chugach NF are closed to motorized use until December 1st or adequate snow to prevent resource damage.

WEATHER ROUNDUP

-TEMPS: have cooled off at all weather stations around Turnagain Pass since yesterday morning by 3-5 degrees. The snow level is forecasted to be around 900′ today

-PRECIP: There has been(0.1 inches) precip that has fallen in 24 hours in the form of mixed snow/rain, and NOAA is forecasting (0.25 inches) of precip for today.

-WIND: I suspect the ridgetop weather station anemometers are iced up and not functioning properly this morning; so its, tough the say exactly what the wind is doing right now. Seattle Ridge at 2400′ appears to be working fine recording light to strong winds in the past 24 hours averaging between 6-36mph with an extreme max gust of 53mph.

AVALANCHE DISCUSSION

The avalanche danger rating will remain at MODERATE due to the potential for small to medium sized human-triggered avalanches along ridges and natural avalanches due to the glide cracks that are widespread throughout the region.

There is a 1/4 inch thick rain crust that extends up to the ridgetops to at least 3500′ and it is widespread throughout the Turnagain Arm area. This crust has all the characteristic to become a very dangerous weak layer as soon as there is more snow on top of it. Right now, there is only a dusting to a couple of inches of snow on top of this crust. Yesterday on Tincan, we obseved that this snow seems to be bonding fairly well at lower to mid elevations where the snow fell at warmer temps. The new snow above 2500′ was not boding as well to this rain crust because of drier colder snow at these higher elevations.

We saw wind transporting snow along ridges while hiking up Tincan yesterday, and the Seattle Ridge weather station recorded some strong winds yesterday. Use extra caution along ridges where there are newly formed wind slabs or pockets of snow that look fat. These isolated pockets will not bond to the ice crust very well today. Pockets like these will be the most likely areas for human-triggered avalanches today.

The glide cracks and glide avalanches continue to be present, with new ones being observed region-wide on a daily basis. Be aware of your travel routes and try to avoid spending time below the cracks. The only way to reduce your risk from glide avalanches is to avoid traveling below the obvious cracks.


This photo shows an example of a glide crack and a glide avalanche on the South face of Cornbiscuit taken on 11-16-10. For scale take note that the crack is 4-6 feet deep. The glide crack on the left hand side of this photo has already avalanched; while, the glide crack on the right is still a hazard that could avalanche any day. Avoid traveling underneath glide cracks just like the one on the right hand side of this photo.

The Nation Weather Service weather forecast for:

WESTERN PRINCE WILLIAM SOUND-

INCLUDING…WHITTIER…SEWARD…GIRDWOOD…MOOSE PASS

500 AM AKST THU NOV 25 2010

.TODAY…SNOW AND RAIN. SNOW ACCUMULATION UP TO 2 INCHES.

HIGHS IN THE 30S. NORTHWEST WIND 15 MPH EXCEPT NORTH 10 TO 25 MPH

NEAR SEWARD.

.TONIGHT…SNOW IN THE EVENING…THEN SCATTERED SNOW SHOWERS

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

20S TO LOWER 30S. NORTHWEST WIND 10 TO 15 MPH EXCEPT NORTH 30 TO

40 MPH NEAR SEWARD.

.FRIDAY…PARTLY CLOUDY. PATCHY MORNING FOG. HIGHS IN THE

LOWER 20S TO LOWER 30S. NORTHWEST WIND 10 TO 15 MPH EXCEPT NORTH

20 TO 30 MPH NEAR SEWARD.

TEMPERATURE / PRECIPITATION

SEWARD 37 29 30 / 80 70 0

GIRDWOOD 33 21 23 / 80 70 0

WEATHER STATION SUMMARY for Turnagain Pass:

3800′-Sunburst Wx Station

Temp (5am): 24 (3 degrees colder than yesterday morning)

Winds: *Anemometer is probably iced up and not working properly*In last 24 hours winds have been light averaging 0-5mph with a light max gust of 6 mph

2400′-Seattle Ridge Wx Station

Temp (5am): 27 (3 degrees colder than yesterday morning).

Winds: In last 24 hours have been light to strong averaging 6-36mph with an extreme max gust of 53mph.

1800′-Center Ridge Wx Station

Temp (6am): 29 (5 degrees colder than yesterday morning)

Precip: 0.1 inches of water, ~40″ of total snopack depth

The next advisory will be issued tomorrow Friday morning 11/26/2010 at 7am. If you get out in the backcountry send us your observations using the button at the top of this page or call and leave a message at 907-754-2369. Thanks and have a great day.

Thu, November 25th, 2010
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. 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.
Observations
Recent Observations for Turnagain Pass
Date Region Location
11/16/23 Turnagain Observation: Tincan Common
11/14/23 Turnagain Observation: Sunburst/Magnum
11/14/23 Turnagain Observation: Seattle Ridge
11/13/23 Turnagain Avalanche: Tincan Trees
11/12/23 Turnagain Observation: Sunburst
11/12/23 Turnagain Avalanche: Goldpan – avalanche
11/11/23 Turnagain Observation: Tincan Common
11/11/23 Turnagain Observation: Taylor Pass – Sunburst
11/10/23 Turnagain Observation: Tincan
11/10/23 Turnagain Observation: Tincan Trees
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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.