Turnagain Pass

Good morning backcountry travelers this is Kevin Wright with the Chugach National Forest Avalanche Information Center on Saturday, February 19th 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 with a complex set of specific concerns. Weather today could dramatically change the avalanche conditions in the new storm snow depending on what happens. Pockets of CONSIDERABLE danger are possible in specific areas that got more snow and more wind. Human triggered sluffs (point releases) are certain today and isolated pockets of soft windslab are likely. If any areas get significant wind the resulting slabs could be easily triggered and dangerous.

AVALANCHE DISCUSSION

Yesterday’s snowfall was light and dry, measuring 8 inches through the Turnagain Pass region. A couple more inches fell overnight. Human triggered sluffs were easily triggered off the steeper slopes and they fell long distances. The sluffing that we witnessed was confined to the upper inches of the new storm snow. The new snow was quite loose, but specific areas had just the smallest bit of cohesiveness, which made slabbing possible in isolated areas. The light density will make it easily affected by changing weather conditions including wind and heat from the sun, which could make wider slabbing a fast change this afternoon.

Summit lake had the largest regional snowfall that we know of and combined with the weakest old layers this could be a dangerous combination today. CNFAIC Staff areas that got more snow or more wind could be dangerous as well. It’s important for the individual to assess the changes as they happen this afternoon. This light, dry snow will be prone to rapid change to more dangerous avalanche conditions if subjected to the right circumstances. Wind transport could move a lot of snow quickly and form triggerable slabs. We’re getting to the warmer side of winter when the sun has heat to it. South facing slopes could catch enough sun today to cause natural sluffing or natural slab release in the new storm snow.

We can’t forget about the old deep slab concerns quite yet. New snow and stress will make it more likely to trigger these deeper slabs, especially in the shallow zones around Summit lake and the Interior Kenai. The worst case scenario today would be triggering a soft slab in the new storm snow that stepped down into the older persistent weak layers and started a larger avalanche. This will be less likely but difficult to predict and much more dangerous than the new storm snow. Check out an example of a recent avalanche that happened this way: See photo and analysis here.

(OUTSIDE FORECAST AREA)

The Hatcher Pass road was closed last night due to avalanche concerns. A reported avalanche put debris across the road 1 mile above Archangel road. Officials will be assessing the hazard this morning to possibly reopen the road today.

Encyclopedia of avalanche terms.

WEATHER ROUNDUP

Yesterday’s storm was widespread from Anchorage to Portage and put more snow in less likely areas. Summit lake got 12 inches, Turnagain Pass 8 –10 inches, and Girdwood 10 inches. Temperatures remained cold to sea level and wind was mostly confined to Turnagain Arm. Clear skies are expected today with wind near Whittier and Seward. Currently wind at the ridgetops is light to moderate, with a chance to increase through the day. Temperatures should remain in the teens and 20s this afternoon.

ANNOUNCEMENTS

The Forest Service is installing winter use bridges across Granite creek in Turnagain Pass. Be aware of an ice road from the Lyon creek bridge south towards Johnson Pass on the West side of the highway. Heavy equipment will also be used in the area.

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 19 2011

…STRONG WIND THIS MORNING THROUGH LATE TONIGHT NEAR WHITTIER…

.TODAY…DECREASING CLOUDS IN THE MORNING…BECOMING MOSTLY SUNNY IN

THE AFTERNOON. BLOWING SNOW NEAR WHITTIER. HIGHS IN THE 20S…COOLEST

INLAND. NORTHWEST WIND 10 TO 20 MPH EXCEPT WEST 30 TO 50 MPH NEAR

WHITTIER AND NORTH 15 TO 30 MPH NEAR SEWARD.

.TONIGHT…MOSTLY CLEAR. BLOWING SNOW NEAR WHITTIER. LOWS ZERO TO 15

ABOVE…COOLEST INLAND. NORTHWEST WIND 10 TO 20 MPH EXCEPT WEST 30 TO

50 MPH NEAR WHITTIER AND NORTH 15 TO 30 MPH NEAR SEWARD.

.SUNDAY…PARTLY CLOUDY IN THE MORNING THEN BECOMING MOSTLY

CLOUDY WITH ISOLATED SNOW SHOWERS. HIGHS IN THE LOWER TO MID 20S.

NORTH AND WEST WIND 10 TO 15 MPH EXCEPT WEST 20 TO 35 MPH NEAR

WHITTIER.

.SUNDAY NIGHT…MOSTLY CLOUDY IN THE EVENING THEN BECOMING PARTLY

CLOUDY. LOWS 10 TO 20 ABOVE…COOLEST INLAND. WEST WIND 10 TO 25 MPH

EXCEPT WEST 30 TO 45 MPH NEAR WHITTIER.

.WASHINGTONS BIRTHDAY…PARTLY CLOUDY. HIGHS IN THE 20S. NORTHWEST

WIND 15 TO 30 MPH EXCEPT WEST 30 TO 45 MPH NEAR WHITTIER.

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

TEMPERATURE / PRECIPITATION

SEWARD 29 13 27 / 0 0 20

GIRDWOOD 22 12 21 / 0 0 20

WEATHER STATION SUMMARY for Turnagain Pass:

-3800′ Sunburst Wx Station-

Temperature 7 degrees and falling. Recent max gust to 15 from the WNW.

-2600′ Seattle Ridge Wx Station-

Temperature 10 on a decreasing trend. Max gust in the last hour of 23 from the NW.

-1800′ Center Ridge Wx Station-

Temperature 14 degrees and decreasing. 8 inches new snow yesterday, anCNFAIC Staff 2 last night with some settlement. Density estimated at 8%.