Turnagain Pass

Good morning backcountry travelers this is Kevin Wright with the Chugach National Forest Avalanche Information Center on Saturday, February 12th 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. New snow this week adds some stress to the old weak layers that have caused recent avalanches. Our greatest concern today remains the deep instabilities that keep us at an elevated caution.

AVALANCHE DISCUSSION

This recent snowstorm affected Turnagain Pass more than Girdwood for a change. Turnagain received 7 inches and 0.6 inches of SWE (snow water equivalent) yesterday. The temperatures gradually dropped and wind remained light during the snowfall. All of that should add up to quality riding conditions in Turnagain if you can stand the cold temperatures.

New snow equals new weight and stress. Without wind the 7 inches should be pleasant loose snow by itself. I’m not too concerned about that new layer avalanching on its own until it gets blown into wind slabs. It does add stress to the already temperamental deep weak layers. Human triggered avalanches will be possible this weekend if you find the sweet spot. Possible trigger points include shallow zones around exposed or lightly buried rocks. This weekend I will be aiming for deeper powder runs and avoiding the steep, rocky, complex terrain.

The most recent avalanche in Turnagain pass was the skier triggered slide on the South face of Magnum on Monday. Since that time nothing has changed to stabilize the responsible weak layers. This avalanche is still extremely relevant this weekend. Snowpit tests are showing the same failures near the Thanksgiving Rain Crust on 2-3mm facets.

It’s been a quiet week in terms of public observations. We haven’t heard of any significant avalanche activity since the avalanche in the photo above. This does not mean that areas are stabilizing on their own. Over the last few days a lack of new human triggered avalanches is only because few people were in the backcountry this week. During a storm people who do get in the backcountry tend to stay on lower slope angles, at lower elevations, and near trees with good visual references. This means that nobody is testing the stability and we don’t get any feedback about the likelihood of human triggers. Don’t confuse a lack of bad information with good information.

All the snowpit profiles are showing an inherently weak structure with a dense, heavy slab on top of weak, loose facets. The old weak layers may fail with each additional snow load until we have a truly significant storm that doesn’t produce avalanches on these layers. So far none of our recent storms have been anywhere near large enough.

Primary concern: Deep persistent instabilities. The same concerns we’ve been talking about all season are still present. Trigger points are most likely to be in areas of shallow snow where your weight can penetrate the stronger slab and collapse the weakness.

Encyclopedia of avalanche terms.

WEATHER ROUNDUP

Most of the last week has had cloudy or snowy weather. A mid-week storm dropped 1 foot of snow in Girdwood and 2-3 inches at Turnagain Pass. Yesterday brought 7 inches of 8% snow to Turnagain and 3-5 inches to Girdwood. Yesterday’s storm came from a different direction than CNFAIC Staff recent storms. It came in cold, with little wind except through Whittier and Portage. Today temperatures are much colder with ridgetops near 0 degrees. Wind is currently light in Turnagain Pass but stronger near Whittier and Seward. Cold and clear weather is predicted through the weekend.

ANNOUNCEMENTS

The Friends of the CNFAIC (FCNFAIC) needs your thoughts! With a new staff of forecasters and a list of previously completed goals, the program is growing and potentially heading in new directions. The FCNFAIC wants to know what you have to say about YOUR avalanche center, so please complete the following anonymous survey by February 20th. Thank you in advance for taking it!

Click here to take survey

or cut and paste the address directly:

https://www.surveymonkey.com/s/THWXVCD

Wendy 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:

WESTERN PRINCE WILLIAM SOUND-

INCLUDING…WHITTIER…SEWARD…GIRDWOOD…MOOSE PASS

500 AM AKST SAT FEB 12 2011

…STRONG WIND THROUGH MONDAY FOR SEWARD AND WHITTIER…

.TODAY…PARTLY TO MOSTLY CLOUDY. ISOLATED SNOW SHOWERS NORTH OF

SEWARD. BLOWING SNOW NEAR WHITTIER. HIGHS 5 TO 15 ABOVE. NORTH TO

WEST WINDS 15 TO 30 MPH. NORTH WINDS 15 TO 30 MPH WITH GUSTS TO 45

MPH NEAR SEWARD. SOUTHWEST WINDS 25 TO 40 MPH WITH GUSTS TO 60 MPH

NEAR WHITTIER.

.TONIGHT…PARTLY CLOUDY. ISOLATED SNOW SHOWERS IN THE EVENING NORTH

AND EAST OF SEWARD. BLOWING SNOW NEAR WHITTIER. LOWS 10 BELOW TO 15

ABOVE…COOLEST INLAND. NORTH TO WEST WINDS 15 TO 30 MPH. NORTH

WINDS 15 TO 30 MPH WITH GUSTS TO 45 MPH NEAR SEWARD. SOUTHWEST WINDS

25 TO 40 MPH WITH GUSTS TO 60 MPH NEAR WHITTIER.

.SUNDAY…MOSTLY SUNNY. HIGHS 5 BELOW TO 15 ABOVE…COOLEST

INLAND. NORTH TO WEST WINDS 15 TO 30 MPH. NORTH WINDS 15 TO 30 MPH

WITH GUSTS TO 45 MPH NEAR SEWARD. SOUTHWEST WINDS 25 TO 40 MPH WITH

GUSTS TO 60 MPH NEAR WHITTIER.

.SUNDAY NIGHT…CLEAR. LOWS 15 BELOW TO 5 ABOVE…COOLEST INLAND.

NORTH WINDS 15 TO 30 MPH WITH GUSTS TO 45 MPH NEAR SEWARD. SOUTHWEST

WINDS 25 TO 40 MPH WITH GUSTS TO 60 MPH NEAR WHITTIER.

.MONDAY…SUNNY. HIGHS 5 BELOW TO 15 ABOVE…COOLEST INLAND. NORTH

WINDS 15 TO 30 MPH WITH GUSTS TO 45 MPH NEAR SEWARD. SOUTHWEST WINDS

25 TO 40 MPH WITH GUSTS TO 60 MPH NEAR WHITTIER.

.MONDAY NIGHT…CLEAR. LOWS 5 BELOW TO 15 BELOW.

TEMPERATURE / PRECIPITATION

SEWARD 12 6 6 / 0 0 0

GIRDWOOD 9 -3 3 / 0 0 0

WEATHER STATION SUMMARY for Turnagain Pass:

-3800′ Sunburst Wx Station-

Temperature 2 degree. Light wind gusting to 12 from the WNW.

-2600′ Seattle Ridge Wx Station-

Temperature 0 degrees. Wind gauge iced over.

-1800′ Center Ridge Wx Station-

Temperature 0 degrees. Up to 7 inches of 8-10% snow fell yesterday.