Turnagain Pass

Happy New Year! This is Kevin Wright with the Chugach National Forest Avalanche Information Center on Saturday, January 1st 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

The avalanche hazard rating is MODERATE today. That’s a little lower than yesterday, but still gives possibility for human triggered avalanches. Today is a good day to read the entire discussion because conditions are complex right now. Deeper wind loaded areas on top of variable buried surface hoar is the primary concern. Natural avalanches are unlikely and human triggered avalanches possible. Expect smaller avalanches on specific terrain features.

AVALANCHE DISCUSSION

Yesterday we observed a few small natural avalanches and a couple of human triggered avalanches were reported. Today, with more time since the snow fell, I expect the hazard to be lower. With the nature of these persistent weak layers I think human triggered avalanches are still very possible, especially if people start to push out onto steeper terrain.

The natural avalanches yesterday were generally on steep leeward slopes where the wind deposited more snow. One of the slabs was mid elevation. All were fairly small and lower volume, most likely breaking at the recent new snow interface on buried surface hoar. The skier triggered avalanche was on Sunburst NW aspect, 3500 ft. elevation, 1 ft. deep, 150 feet wide, fell 900 vertical feet and started on a 38-degree slope. One of our observers did a crown profile shortly after it was triggered and found it slid on buried surface hoar, not affecting the deeper facets layers. An extended column test failed with full propagation while the column was being isolated! ECTPV. By contrast, anCNFAIC Staff observer on Tincan got no failures with compression tests and hard failures with shovel shear tests. This emphasizes the variability of this weak layer and the hazard right now.

CNFAIC Staff observations showed more dangerous conditions in the Girdwood valley, which got a little more snow out of this storm than Turnagain pass. Observers in the Winner creek area on Thursday night found significant whoomphing and remotely triggered a small slab just uphill of the Cat road. Explosive triggers yesterday on previously uncontrolled slopes had one result with extremely wide propagation, connecting across multiple shallow ridgelines and gullies.

This relatively small amount of snow over the last few days has caused instability, but hasn’t affected the deeper concerning weak layers in Turnagain pass. Right now we are most concerned with the new snow and an inconsistent (spatially variable) layer of surface hoar. I think the slabs are going to be found on variations of West aspects including cross loaded North and South facing gullies. The slab seems to be difficult to trigger, but will initiate from the hard to define sweet spots.

For the long-term outlook, I’m still very concerned about deeper weak layers. The consensus in the avalanche community is that these layers will start to fail when we do get a big enough snow load. Pay attention to the future storms.

Encyclopedia of avalanche terms.

WEATHER ROUNDUP

Yesterday Turnagain pass showed a thin rain crust near the road, but higher up the snow got a little drier with 2-3 inches of new. Overnight a couple inches have fallen at higher elevations in Girdwood, but probably not in Turnagain pass. Wind is still high at the ridge tops and temperature is currently above freezing at the 1800 ft. Center ridge station. Today a little more precip is predicted for this region with strong wind. Flow is continuing from the South, giving Seward and the South coast the majority of the precipitation, and dropping only small amounts through Turnagain arm.

Lisa 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. Enjoy the New Year holiday!

The NWS weather forecast for:

WESTERN PRINCE WILLIAM SOUND-

INCLUDING…WHITTIER…SEWARD…GIRDWOOD…MOOSE PASS

500 AM AKST SAT JAN 1 2011

…STRONG WIND THROUGH TONIGHT FOR TURNAGAIN ARM AND PORTAGE

VALLEY…

..STRONG WIND SUNDAY NIGHT AND MONDAY FOR TURNAGAIN ARM AND PORTAGE

VALLEY…

.TODAY…RAIN…MIXED WITH SNOW AT TIMES THIS MORNING AT HIGHER

ELEVATIONS AND INLAND. LITTLE SNOW ACCUMULATION. HIGHS IN THE MID 30S

TO LOWER 40S. THROUGH PORTAGE VALLEY AND TURNAGAIN ARM…EAST WIND

INCREASING TO 30 TO 50 MPH WITH GUSTS TO 65 MPH THIS MORNING.

ELSEWHERE…SOUTHEAST WINDS 20 TO 40 MPH.

.TONIGHT…RAIN AND SNOW. NO SNOW ACCUMULATION. LOWS IN THE UPPER 20S

TO UPPER 30S. THROUGH PORTAGE VALLEY AND TURNAGAIN ARM…EAST WIND

INCREASING TO 30 TO 50 MPH WITH GUSTS TO 65 MPH THIS MORNING.

ELSEWHERE…SOUTHEAST WINDS 20 TO 40 MPH.

.SUNDAY…RAIN LIKELY…MIXED WITH SNOW IN THE MORNING. SNOW

ACCUMULATION UP TO 1 INCH. HIGHS IN THE UPPER 20S TO UPPER 30S.

SOUTHEAST WIND 20 TO 35 MPH.

.SUNDAY NIGHT…RAIN AND SNOW LIKELY. LOWS IN THE MID 20S TO MID

30S. THROUGH PORTAGE VALLEY AND TURNAGAIN ARM…EAST WIND INCREASING

TO 25 TO 45 MPH WITH GUSTS TO 60 MPH THIS MORNING.

ELSEWHERE…SOUTHEAST WINDS 20 TO 35 MPH.

.MONDAY…RAIN AND SNOW LIKELY IN THE MORNING…THEN A CHANCE OF

RAIN AND SNOW IN THE AFTERNOON. HIGHS IN THE LOWER 30S TO LOWER

40S. THROUGH PORTAGE VALLEY AND TURNAGAIN ARM…EAST WIND INCREASING

25 TO 45 MPH WITH GUSTS TO 60 MPH THIS MORNING. ELSEWHERE…SOUTHEAST

WINDS 20 TO 35 MPH.

.MONDAY NIGHT…MOSTLY CLOUDY WITH A CHANCE OF RAIN AND SNOW. LOWS IN

THE 30S.

.TUESDAY…MOSTLY CLOUDY WITH A CHANCE OF SNOW AND RAIN. HIGHS IN THE

30S.

.TUESDAY NIGHT THROUGH THURSDAY…MOSTLY CLOUDY WITH A CHANCE OF

SNOW. LOWS IN THE 20S. HIGHS 25 TO 35.

.THURSDAY NIGHT…MOSTLY CLOUDY WITH A CHANCE OF SNOW. LOWS IN THE

TEENS.

.FRIDAY…PARTLY CLOUDY. HIGHS IN THE 20S.

TEMPERATURE / PRECIPITATION

SEWARD 37 35 35 / 80 80 60

GIRDWOOD 36 33 33 / 70 60 60

WEATHER STATION SUMMARY for Turnagain Pass:

-3800′ Sunburst Wx Station-

No updates since 1000 last night.

-2600′ Seattle Ridge Wx Station-

Temperatures to 28 degrees. Wind steady in the 30s, gusting in the 40s from the SE.

-1800′ Center Ridge Wx Station-

Warm temperatures, currently 34 degrees. No new snow or rain recorded since yesterday.