Turnagain Pass

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

BOTTOM LINE

The avalanche hazard rating is MODERATE for recent wind slabs and deep persistent instabilities. A chance of snow today will likely have only a small effect on the stability, but pay attention if the snowfall is deeper than expected.

AVALANCHE DISCUSSION

Snow today is worth keeping track of. The weather service is predicting small amounts in Turnagain pass today, diminishing this evening. Accumulation may be greater to the North of Anchorage. New snow with wind could change the stability rating if it gets deep enough.

Primary avalanche concern in Turnagain pass is recent wind slab. The region got hammered by strong wind after the dry snowfall 7 days ago. The light density snow was easily transported by the wind, resulting in redistribution and stiffening of that layer. Natural avalanche activity during the wind event was widespread. Since the wind diminished the hazard should be dropping quickly for this specific type of avalanche. Human triggered wind slabs may still be possible on lee aspects and cross loaded slopes.

Secondary concern remains the old deep instabilities. These faceted weak layers are most likely to be triggered in shallow zones and specific shallow points in deeper snowpacks. The frequency between events on these layers is getting longer, and it may not be a serious problem in Turnagain Pass again until we get a new storm load. Given a big enough stress in the right spot I think you could still trigger these layers. Shallower zones such as the Interior Kenai are still a wild card right now and should be approached in a more cautious manner than Turnagain Pass.

WEATHER ROUNDUP

The last couple days in Turnagain have been clear with light wind. The surface snow is still heavily winded from the storm early in the week. Today snow is expected through southcentral. The system is moving from the West, which could hit Anchorage harder than Turnagain Arm. Wind last night was strong in Summit and moderate in Turnagain. As the storm passes over stronger wind is expected through Turnagain Arm and Portage. Warmer temperatures are expected briefly, quickly transitioning to colder air as the front moves through.

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.

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:

WESTERN PRINCE WILLIAM SOUND-

INCLUDING…WHITTIER…SEWARD…GIRDWOOD…MOOSE PASS

500 AM AKST FRI FEB 25 2011

…STRONG WIND THIS AFTERNOON THROUGH SUNDAY NEAR WHITTIER…

.TODAY…SNOW SHOWERS IN THE MORNING…THEN PARTIAL CLEARING WITH

ISOLATED SNOW SHOWERS IN THE AFTERNOON. SNOW ACCUMULATION UP TO 2

INCHES. HIGHS IN THE LOWER TO MID 30S. VARIABLE WIND 15 MPH EXCEPT

SOUTHEAST 15 TO 30 MPH THROUGH PORTAGE VALLEY AND TURNAGAIN ARM

SHIFTING TO THE WEST IN THE AFTERNOON. NEAR WHITTIER…VARIABLE WIND

10 MPH INCREASING TO WEST 15 TO 30 MPH WITH GUSTS TO 45 MPH IN THE

AFTERNOON.

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

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

EXCEPT WEST 30 TO 45 MPH WITH GUSTS TO 60 MPH NEAR WHITTIER. NEAR

SEWARD…NORTH WIND 25 TO 40 MPH.

.SATURDAY…MOSTLY SUNNY. HIGHS IN THE LOWER TO MID 20S. NORTHWEST

WIND 10 TO 20 MPH EXCEPT WEST 30 TO 45 MPH WITH GUSTS TO 60 MPH NEAR

WHITTIER. NEAR SEWARD…NORTH WIND 25 TO 40 MPH.

.SATURDAY NIGHT…CLEAR. LOWS 10 BELOW TO 15 ABOVE…COOLEST

INLAND. NORTHWEST WIND 10 TO 20 MPH EXCEPT WEST 30 TO 45 MPH WITH

GUSTS TO 60 MPH NEAR WHITTIER. NEAR SEWARD…NORTH WIND 25 TO 40 MPH.

.SUNDAY…SUNNY. HIGHS IN THE LOWER TO MID 20S. NORTHWEST WIND

10 TO 15 MPH WITH GUSTS TO 30 TO 45 MPH NEAR SEWARD AND WHITTIER.

TEMPERATURE / PRECIPITATION

SEWARD 36 23 26 / 30 0 0

GIRDWOOD 31 11 21 / 80 30 0

WEATHER STATION SUMMARY for Turnagain Pass:

-3800′ Sunburst Wx Station-

Temperature 28. West wind gusting to 33 in the last hour.

-2600′ Seattle Ridge Wx Station-

Temperature 28. Light to moderate wind overnight.

-1800′ Center Ridge Wx Station-

Temperature 24 degrees. No new snow recorded by 0600.