Turnagain Pass

Good morning backcountry travelers this is Kevin Wright with the Chugach National Forest Avalanche Information Center on Friday, December 10th 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).

ANNOUNCMENTS

This weekend, December 11-12, there will be an Interagency Avalanche Rescue Training taking place at Turnagain Pass. Alaska Mountain Rescue Group, Alaska Search and Rescue Dogs, Alaska State Troopers, Nordic Ski Patrol, and US Forest Service will be some of the agencies participating in this two day event. There will be scenarios on both the motorized and non-motorized sides of Turnagain Pass. The parking lot on the eastern side of the Seward Highway will still be open to the public, but will also be the location for the staging area for this training exercise. There will be some helicopter use in the area for the purpose of this training event. If you have any comments or concerns, please contact Matt Murphy by phone at 907-754-2349 or email at mattmurphy@fs.fed.us. Thank you for your cooperation with this important safety training.

AVALANCHE DISCUSSION

Today the avalanche hazard is MODERATE. Hazard may be on an increasing trend if new snow accumulates today. Since the last storm the snow has settled in and stabilized to the point where no reports are coming in about new avalanches. I wouldn’t say that everything is completely stable, but most areas are proving safe to travel with normal precautions. Use extra caution in areas where wind loading has occurred or in convex and unsupported terrain.

The last storm cycle with new snow on top of surface hoar had the reactions we expected with widespread activity just after the storm and gradual stabilization after several days. Just remember that those surface hoar layers are notoriously persistent. Given the right combination of increased load (a person or new snow) we could see those layers reactivate. The most significant observations we had yesterday are from the Girdwood Valley where skiers reported large collapsing and full propagation failures in snow pits. This indicates that the buried surface hoar layer is probably still reactive in some areas.

Yesterday we snowmachined up Seattle ridge. The first thing that jumped out at us was the widespread surface hoar to the ridge top. This layer is sitting on top of soft stellars (good sign), but is very well developed (bad sign). We’ll have to pay close attention to this layer as the next snowfall arrives. This does not affect today’s stability, but keep that information tucked away for when the next snowfall arrives.

Surface hoar crystals on Seattle ridge. A future weak layer when it gets buried.

We dug a pit in Stock Run Bowl (Bowl 2) and found no real surprises. Column tests had very hard failures on compression, but a few weaknesses showed with shovel shears. Multiple clean failures happened on old buried surface hoar. For some reason we could not find the rain crust in this pit location up to 5 feet deep, although it was prevalent in more scoured areas. Right now our primary instability is the buried surface hoar with wind slab on top of it. Check the photo gallery for that pit profile from yesterday.

WEATHER ROUNDUP

The last few days have brought light wind and clear skies to upper elevations. Surface hoar has been growing at a significant rate.

Today the National Weather Service is forecasting 3-10 inches for upper elevations and moderate wind at the ridge tops. Any extra weight in the form of new snow will increase the likelihood of avalanches. Keep this in mind if the new snow accumulates this afternoon.

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:

INCLUDING…WHITTIER…SEWARD…GIRDWOOD…MOOSE PASS

500 AM AKST FRI DEC 10 2010

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

TEENS TO NEAR 30…COOLEST INLAND. VARIABLE WIND 10 MPH EXCEPT NORTH

20 TO 35 MPH NEAR SEWARD. NEAR WHITTIER…SOUTHWEST WIND 15 TO 25 MPH

.TONIGHT…SNOW SHOWERS. SNOW ACCUMULATION UP TO 2 INCHES. LOWS IN

THE LOWER TEENS TO LOWER 30S…COOLEST INLAND. VARIABLE WIND TO 10

MPH. NEAR SEWARD…NORTH WIND 10 TO 20 MPH.

.SATURDAY…SNOW LIKELY. SNOW ACCUMULATION UP TO 2 INCHES. HIGHS

IN THE MID 20S TO UPPER 30S. VARIABLE WIND 10 MPH EXCEPT NORTH

10 TO 25 MPH NEAR SEWARD.

.SATURDAY NIGHT…CLOUDY WITH ISOLATED SNOW SHOWERS. LOWS 15 TO

25. LIGHT WINDS EXCEPT NORTH 15 TO 25 MPH NEAR SEWARD.

.SUNDAY…MOSTLY CLOUDY WITH ISOLATED SNOW SHOWERS IN THE

MORNING…THEN PARTLY CLOUDY IN THE AFTERNOON. HIGHS IN THE LOWER

20S TO MID 30S…COOLEST INLAND. VARIABLE WIND TO 10 MPH. NEAR

SEWARD…NORTH WIND 15 MPH.

.SUNDAY NIGHT…MOSTLY CLEAR. LOWS IN THE TEENS.

.MONDAY THROUGH WEDNESDAY…PARTLY CLOUDY. HIGHS 15 TO 25. LOWS

5 TO 15.

.WEDNESDAY NIGHT AND THURSDAY…PARTLY CLOUDY. LOWS 5 BELOW TO

5 ABOVE. HIGHS 5 TO 15 ABOVE.

TEMPERATURE / PRECIPITATION

SEWARD 29 25 33 / 80 70 60

GIRDWOOD 21 20 32 / 100 100 60

WEATHER STATION SUMMARY for Turnagain Pass:

-3800′ Sunburst Wx Station-

Temperatures dropped in the last 24 hours to the current 16 degrees. Wind has been very light.

-2600′ Seattle Ridge Wx Station-

Wind data may be suspect. We knocked the rime off the station yesterday and the meter is spinning freely now, but the direction indicator may be wrong. Generally light wind in the last 24 hours. Dropping temperatures.

-1800′ Center Ridge Wx Station-

No new snow. Temperatures dropped from 22 to 11 degrees since yesterday.