Good Morning backcountry travelers, this is Carl Skustad with the Chugach National Forest Avalanche Information Center on Friday, February 27, 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. This advisory does not apply to operating ski resorts or highways/railroads.
MOUNTAIN WEATHER ROUND UP FOR THE LAST 24 HOURS
-General Weather Observations-
Mild weather in store for us again today as weak pressure systems battle over Southcentral AK. Expect gusty winds at times as a result of the passing systems pressure gradients.
–The DOT weather station near the crest the highway at Turnagain Pass at 1000 feet–
Is recording a temp of 35 degrees (2 degrees cooler than yesterday) with light winds and zero new snow.
–The NRCS Center Ridge weather station at 1800 feet in Turnagain Pass–
Has a temp of 16 degrees (3 degrees colder than yesterday). 0 inches water and 0 inch of new snow has been recorded. Total snowpack depth is still 67″.
–The Sunburst weather station at 3800 feet in Turnagain Pass–
Shows a temperature of 10 degrees (2 degrees colder than yesterday). Winds have been averaging 10 mph with gust into the 20’s out of the west north west.
-Surface Analysis Maps-
Pressure systems are battling over the area. A wave of precipitation heading out way for Saturday.
Next system is over Dillingham, Aniak, and Bethel.
Primary avalanche concerns
-Above 3000 feet. Hard wind slabs. Multiple density layers/interfaces in the top 1-2 feet of snow with potential for human-triggered avalanches.
-Below 3000 feet. Rain crust buried under 1-4 feet of surface snow. Avalanches have been common and widespread on this lower elevation instability. There is a layer of faceted snow on both sides of this crust. Be very careful on steep slopes in Lost Lake, Placer Valley, Seattle Creek, and Girdwood Valley. This weak layer will be a problem for some time!
AVALANCHES AND SNOWPACK
Elevated Caution is still advised. The danger rating is MODERATE. Natural avalanches unlikely. Human triggered avalanches possible today.
We still have some questions about the current stability of our snowpack. In general our stability has improved over the last week but by no means are we out of the woods. We will have a tricky snowpack the rest of the season.
Yesterday we climbed up Sunburst and found a grab bag of wind slab layers. Last Friday’s wind event really hammered much of the snowpack from Girdwood to Summit Lake. In many areas these wind slabs are very sensitive but very small, measuring only a couple of inches. Near the ridge tops these wind slabs are much thicker and stiffer, measuring 1-2 feet. We found very easy failures on the smaller slabs, (CT1 Q2 (x2)). 1 to 1.5 feet deep we found harder test results (CT24,25 Q2). The surface varies from boiler plate to sastrugi (see photo).
Sunburst Ridge-Notice erosional features left after last Fridays wind event. Sastrugi is the name we give the snow surface after it has been eroded by strong winds.
The main problem with upper elevations today relates to the tricky nature of hard slabs. It’s common for people to get way out in the middle of a hard slab before it avalanches. The photo gallery has a photo of a small hard slab avalanche that was skier triggered while skinning up Lipps last Saturday.
-That rain crust below 3000 feet continues to show itself. One of our observers found that rain crust Tuesday on the Sunnyside of Turnagain Pass (climbers left of Repeat Offender). In his extended column test, he found propogation across the entire column with a very clean and fast Q1/Q2 shear. We do not see many Q1 shears. Lisa saw the first Q1 of the season on Tincan last Saturday. Q1s are bad. Anytime you see super fast clean shears, you should stay away from those slopes. AnCNFAIC Staff observation came from Eddy’s on Wed. He found buried surface hoar at 2500 ft. This is a serious concern because many pits have found this layer and many have not, providing much spacial variability to our snowpack. Buried surface hoar is a very sneaky layer and is hard to find but when you do find it’s a notorious weak layer. It’s a weak layer responsible for many fatalities.
Safe terrain management and strict travel rituals are still essential right now.
WESTERN PRINCE WILLIAM SOUND-
500 AM AKST FRI FEB 27 2009
.TODAY…MOSTLY SUNNY. HIGHS IN THE UPPER 20S TO MID 30S. NORTH AND
WEST WIND TO 15 MPH IN THE MORNING BECOMING LIGHT. NEAR SEWARD AND
WHITTIER…STRONGER WIND GUSTING TO 30 TO 40 MPH DIMINISHING BY
.TONIGHT…INCREASING CLOUDS IN THE EVENING. SNOW AFTER MIDNIGHT.
SNOW ACCUMULATION 1 TO 2 INCHES. LOWS IN THE 20S. VARIABLE WIND 10
.SATURDAY…SNOW. SNOW ACCUMULATION 1 TO 3 INCHES. HIGHS IN THE
UPPER 20S TO MID 30S. VARIABLE WIND TO 10 MPH.
.SATURDAY NIGHT…DECREASING CLOUDS. ISOLATED SNOW SHOWERS IN THE
EVENING. LOWS IN THE MID TEENS TO LOWER 20S. NORTH TO WEST WIND 10 TO
20 MPH. STRONGER WINDS GUSTING TO 25 TO 35 MPH NEAR SEWARD AND
.SUNDAY…MOSTLY SUNNY. HIGHS IN THE MID 20S TO LOWER 30S.
NORTHWEST WIND 10 TO 20 MPH. STRONGER WINDS GUSTING TO 25 TO 35 MPH
NEAR SEWARD AND WHITTIER.
TEMPERATURE / PRECIPITATION
SEWARD 31 25 32 / 0 100 100
GIRDWOOD 29 22 29 / 0 80 100
This concludes today’s avalanche advisory the next advisory will be on Saturday, February 28th. Thanks and have a great day.