Turnagain Pass

Good morning backcountry travelers this is Matt Murphy with the Chugach National Forest Avalanche Information Center on Thursday February 25th at 7 am. 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).

WEATHER ROUNDUP

-The winds have been light at all ridge top weather stations but they are starting to pick up a bit this morning with some moderate gusts

-The current radars show scattered precip over PWS moving NE, but a good flow of moderate precip on the Kenai radar moving right toward Anchorage.

-In the last 24 hours (5am-5am), the snotel sites recorded 0 inches of water at Turnagain Pass, 0 inches at Grandview, and 0 at Summit Creek. The total snowpack has settled 1-2” since yesterday

-Temps are colder this morning at all wx stations compared to yesterday. Temps range from 30 degrees F at sea-level and 22 degrees F at 3800′. High temps still made it as high as 31 degrees at 3300′ yesterday afternoon.

AVALANCHE DISCUSSION

Today’s avalanche danger is MODERATE due to the unpredictable nature of glide cracks and cornices. We have had recent glide crack and cornice avalanche activity; so, these types of natural avalanches are possible today. Glide cracks can be easy to avoid because you can see them, but they are difficult forecast. A very small glide crack avalanche was observed on Center Ridge two days ago. CNFAIC Staff than glide cracks and cornices, the snowpack in general is showing good to very good stability. The avalanche danger scale does not fit very well with today’s conditions.

The two specific areas of concern today are:

-Glide Cracks

Glide cracks are those crevasse like features in the snow that open up all the way to the ground. The snowpack is starting to pull away from the ground in many locations creating these glide cracks. Glide cracks are very difficult to predict. Sometimes they avalanche when it is cold, sometimes when it is warm, sometimes when it rains, sometimes when it snows. The point is that we are having an active glide crack cycle right now. At least one glide crack avalanche was observed 2/23/2010 below 2000′ on Center Ridge. When glide cracks avalanche, they fail all the way to the ground. We also observed a dirty pile of debris on a northern aspect on Tincan Ridge (beyond Todd’s Run). We were not able to see the origin of that dirty pile, but there is a good chance that it was a glide crack avalanche as well. Avoid traveling underneath or anywhere near glide cracks especially during times that they are actively moving like they are right now.

-Cornices

We received a report of a close call that happened on Monday 2/22/2010 on the cornice above Zero Bowl (No Name Bowl) at the top of the snowmachine up-track on Seattle Ridge. A snowmachiner accidently triggered a chunk of cornice that fractured underneath the ski of his snowmachine. We took a closer look at the cornices along Seattle Ridge from 3000′ in Warm-Up Bowl to 2400′ in Main Bowl near Widowmaker. We found: several cornice failures, cracks at the roots of cornices that are difficult to see but easy and dangerous to fall into, sagging cornices, and generally much larger cornices than we have seen all year. Be especially careful along ridges with cornices today.

Glide cracks and cornices are total wild cards. Both of these features are very difficult to predict. Since we are seeing recent activity with both of these features right now, this is one of those times to be extra careful anywhere near cornices and glide cracks. Avoid traveling underneath, along the side, above, or anywhere near glide cracks or cornices today.

WEATHER FORECAST (National Weather Service)

WESTERN PRINCE WILLIAM SOUND-

INCLUDING…WHITTIER…SEWARD…GIRDWOOD…MOOSE PASS

500 AM AKST THU FEB 25 2010

…STRONG WIND FRIDAY MORNING THROUGH FRIDAY AFTERNOON IN WHITTIER…

.TODAY…NUMEROUS SNOW SHOWERS. SNOW ACCUMULATION UP TO 2 INCHES.

HIGHS IN THE 30S. LIGHT WINDS.

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

LOWS 15 TO 25. VARIABLE WIND 10 MPH EXCEPT NORTH AND WEST

WIND INCREASING TO 15 TO 30 MPH NEAR SEWARD AND WHITTIER.

.FRIDAY…MOSTLY SUNNY. HIGHS IN THE MID 20S TO LOWER 30S.

VARIABLE WIND 10 MPH EXCEPT NORTH AND WEST WIND 15 TO 30 MPH

NEAR SEWARD AND WHITTIER. GUSTS TO 45 MPH IN WHITTIER.

Temperature / Precipitation

SEWARD 35 22 28 / 40 0 0

GIRDWOOD 32 18 27 / 90 50 0

Short Term Weather Model Forecasts (NAM, WRF, GFS) for the Kenai Mountains near Turnagain Pass

Sea-level: temps are forecasted between 18-32 and between 0.0”-0.1” of water forecasted 3000′: temps are forecasted in the range of 23-32 degrees F with winds 5 mph

6000′: temps are forecasted in the range of 14-23 degrees F with winds 10-15 mph

WEATHER STATION SUMMARY for last 24 hours at TURNAGAIN PASS

3800′-Sunburst Wx Station

Current Temp: 22 (2 degrees colder than yesterday)

Winds: In last 24 hours winds have been light averaging 2-8mph with light gusts up to 11mph. *Note: Wind direction is from unusual direction this morning. Winds are out of the West when they are typically out of the East.

2600′-Seattle Ridge Wx Station

Winds: In last 24 hours winds have been light averaging 1-13mph with a moderate gust of 19mph

1800′-Center Ridge Wx Station

Current Temp: 25 degrees (5 degrees colder than yesterday)

Precip: 0 new water, 0 new snow, 1” of total snowpack settlement/melting for total snowpack depth of 88”

Thanks for checking today’s avalanche advisory. The next one will be posted tomorrow Friday February 26th.