Turnagain Pass

GENERAL ANNOUNCEMENTS

Good Morning backcountry travelers, this is Carl Skustad with the Chugach National Forest Avalanche Information Center on Friday, January 30, 2009 at 7am. This will serve as a general backcountry avalanche advisory issued 5 days a week Wednesday-Sunday for the Turnagain Arm area (Turnagain Pass is the core advisory area). Local variations always occur.

MOUNTAIN WEATHER ROUND UP

In the last 24 hours…

-General Weather Observations-

Temperatures have cooled off this morning and winds are light. Yesterday afternoon we had 20 to 30 mph winds out of the east transporting snow on ridge tops. Snow showers are forecasted for the area.

–The DOT weather station near the crest the highway at Turnagain Pass at 1000 feet–

Is recording a temp of 22 degrees (5 degrees cooler than yesterday), calm winds averaging 2 mph and the same total snowpack depth of 41 inches (same as yesterday).

–The NRCS Center Ridge weather station at 1800 feet in Turnagain Pass–

Has a temp of 19 degrees (7 degrees cooler than yesterday). Yesterday morning an inch of snow fell but settled during the day to keep the total snowpack depth at 61 inches.

–The Sunburst weather station at 3800 feet in Turnagain Pass–

Is recording a temperature of 16 degrees F (4 degrees cooler than yesterday). Winds have been light in the single digits from the east southeast.

-Surface Analysis Maps-

The double barreled 986 low thats over the area currently is sliding southwest in to the gulf. Cooler artic air is pushing in.

-Radar-

Im not seeing allot of precip on tap for the Turnagain Arm area today. Anchorage will get a few more snow showers this morning as a cell moves up the Knik Arm. The Middleton Radar shows fairly clear skies with scattered pockets of precip.

AVALANCHE HAZARDS

Primary avalanche concerns

-Surface wind slabs on alpine ridges

AVALANCHE AND SNOWPACK

Bottom Line

Normal caution is advised. Wind slabs are present in most alpine locations on multiple aspects. 6 to 12+ inch wind slabs would be dangerous if you unexpectedly triggered one and it carried you over complex terrain like cliff bands or into terrain traps.

Discussion

Yesterday we intentionally triggered multiple small windslabs on Tincan Ridge. Most of the south aspect windslabs were small, 2 to 10 inches, and were being actively formed from northerly winds. The north facing aspects held deeper wind slabs from Tuesdays winds. The notable wind slab we released ran 1000 feet down Todd’s Run. This slab was 2 to 12 inches deep and 50 ft wide. Triggering small avalanches from cornices or wind slabs can work as good slope stability tests. Advanced experience is required.

Tincan Ridge, notice the northerly winds actively loading the south faces

We dug a pit at 4000 ft and found all the weak layers from the season. None of them were that responsive. CT scores in the mid 20’s to 30 plus. We found January facets and even October facets and surface hoar. We haven’t heard of any easy test results on any weak layers in over a month. No human triggered avalanches have been reported. My discussion is not the green light for everything. You will find varying conditions above tree line and I am sure you could find avalanches that could ruin your day on complex alpine terrain. Localized winds will be important to watch.

A wind slab we kicked loose ran from 3900 ft to 2700 ft, see the toe of the debris down in the bowl

WEATHER FORECAST

WESTERN PRINCE WILLIAM SOUND-

INCLUDING…WHITTIER…SEWARD…GIRDWOOD…MOOSE PASS

640 AM AKST FRI JAN 30 2009

.TODAY…SNOW SHOWERS. AREAS OF BLOWING SNOW. SNOW ACCUMULATIONS 1

TO 3 INCHES. HIGHS IN THE UPPER TEENS TO MID 20S. NORTH TO WEST

WINDS 10 TO 20 MPH…GUSTS TO 30 MPH NEAR SEWARD AND WHITTIER

DEVELOPING BY AFTERNOON.

.TONIGHT…CLOUDY WITH SCATTERED SNOW SHOWERS. AREAS OF BLOWING

SNOW. LOWS 5 TO 15 ABOVE. NORTH TO WEST WINDS 10 TO 20 MPH. GUSTS TO

35 MPH NEAR SEWARD AND WHITTIER.

.SATURDAY…MOSTLY CLOUDY WITH ISOLATED SNOW SHOWERS. HIGHS IN

THE TEENS. NORTH WIND 15 MPH. NEAR SEWARD…NORTH WIND 30 MPH

DECREASING TO 15 MPH IN THE AFTERNOON. GUSTS TO 30 MPH IN THE

MORNING.

.SATURDAY NIGHT…MOSTLY CLOUDY WITH ISOLATED SNOW SHOWERS. LOWS

ZERO TO 10 ABOVE. VARIABLE WIND 10 MPH.

.SUNDAY…DECREASING CLOUDS. ISOLATED SNOW SHOWERS. HIGHS IN THE

TEENS. NORTHWEST WIND 10 TO 15 MPH WITH GUSTS TO 30 MPH EXCEPT

NORTH 15 TO 25 MPH NEAR SEWARD.

.SUNDAY NIGHT…MOSTLY CLEAR. LOWS 5 TO 15 ABOVE.

TEMPERATURE / PRECIPITATION

SEWARD 25 10 15 / 60 40 20

GIRDWOOD 22 6 13 / 60 40 20

This concludes today’s avalanche advisory the next advosory will be on Saturday Jan 31. Thanks and have a great day.