Good morning backcountry travelers, this is Lisa Portune with the Chugach National Forest Avalanche Information Center on Sunday, December 7, 2008 at 7am. This will serve as a general backcountry avalanche advisory issued for the Turnagain Arm area. Local variations always occur. Note: We are now issuing regular advisories 5 days a week Wednesday-Sunday.
INTERAGENCY AVALANCHE RESCUE TRAINING
On the weekend of December 13-14, there will be an avalanche rescue training taking place at Turnagain Pass. Please be aware of rescue workers, helicopters, and areas set up for rescue training drills.
MOUNTAIN WEATHER ROUND UP
In the last 24 hours…
-The Center Ridge weather station at 1800 feet in Turnagain Pass recorded no new snow with 2 inches of settlement for a total snowpack depth of 44 inches. The temperature this morning is 31 degrees F (2 degrees colder than yesterday).
-The Sunburst weather station at 3800 feet in Turnagain Pass recorded light winds averaging 5-10 mph with gusts in the teens out of the SE for most of the day yesterday. Max’s weather station at 3200 feet in the Girdwood Valley also recorded light and variable winds.
Ridgetop winds are currently light with temps ranging from 27-29 degrees F (2-3 degrees colder than yesterday).
Not much happened this past week weather-wise CNFAIC Staff than the southerly flow keeping temps well above normal and weak surface lows spitting out a bit of precip. Turnagain Pass received about 4 inches of snow spread out over the week with strong easterly winds on Wednesday. The upper elevations of the Girdwood Valley got 10 inches on Wednesday, but that’s about it. Temps just dipped below 32F this morning at the Center Ridge weather station after being above freezing for the last 72 hours.
Expect maybe anCNFAIC Staff inch of snow today at the higher elevations with mostly cloudy skies. Winds will be light and variable averaging 10 mph with ridgetop temps in the upper 20’s and lower 30’s. Our next chance for snow looks to be Monday as a low moves into the gulf bringing strong easterly winds and cooler temps.
Our primary avalanche concern continues to be a persistent weak layer of buried surface hoar about 3-5 feet deep sitting on top of weak sugary October facets near the ground. Most all of the human-triggered avalanches that happened during the last week of November failed on this layer and ripped out to the ground. Our next significant snow load may be enough to trigger anCNFAIC Staff round of avalanches on this layer. In the meantime be aware of thin, shallow areas of the snowpack near rock outcrops and scoured ridges where this weak layer is closer to the surface and thus more easily impacted by skis, boards, or snowmachines.
AVALANCHE AND SNOWPACK DISCUSSION
Yesterday Sean and I slogged our way up Max’s in the Girdwood Valley for a look at the snowpack. The snow was like mashed taters with pinwheels rolling down steep slopes as the freezeline climbed as high as 3000 feet. We dug a pit at 2300 feet and easily found that buried surface hoar on top of October facets about 3.5 feet down. The total snowpack depth on this west aspect was 4.5 feet. Our tests showed decent stability on this layer but the shears were still clean (CTH21-23 Q2 @ 115cm)…certainly not a green light to just go for it. We decided not to continue upward to the steeper slopes just below the weather station.
It has been about a week since our last reported natural or human-triggered avalanche most likely because we have not received enough of a snow load to tip the stress vs. strength balance. What is this magic number? AnCNFAIC Staff ½ inch of water maybe? I’d really like to see us get walloped by a massive storm that cleans out our snowpack with a natural avalanche cycle. The bottom line is we currently have a 3-5 ft. dense slab on top of a foot of weak sugar snow near the ground…not the ideal way to start the season. Although obvious signs of instability (like shooting cracks and whumphing) may not be present, I would still avoid big exposed slopes over 35 degrees. The snowpack is much shallower and weaker down by Summit Lake, with one of our observers (thanks Funhog!) reporting widespread whumphing from 1700 to 2500 ft. elevation yesterday.
***Although outside of our advisory area, one of the Chugach State Park rangers (thanks Ian!) reported seeing a skier triggered avalanche yesterday on an unnamed peak just to the west of Harp Mtn. (S. Fork Eagle River) at 3200′ on a SW aspect. It appeared to be 300 feet wide, 12-16 inches deep at the crown face, and failed at the ground.
This concludes today’s advisory; the next advisory will be Wednesday, December 10th. If you are out in the backcountry and have the chance, send us your observations. Simply click on “observations” next to the advisory page. Thanks and have a great day!
The weather forecast for:
WESTERN PRINCE WILLIAM SOUND-
500 AM AKST SUN DEC 7 2008
…STRONG WIND MONDAY AFTERNOON AND MONDAY NIGHT…
.TODAY…RAIN AND SNOW. NO SNOW ACCUMULATION. HIGHS IN THE 30S. LIGHT
WINDS. NEAR WHITTIER…LIGHT WINDS BECOMING WEST 15 MPH IN THE
.TONIGHT…MOSTLY CLOUDY. A CHANCE OF SNOW AND RAIN SHOWERS IN THE
EVENING…THEN A SLIGHT CHANCE OF SNOW AFTER MIDNIGHT. LOWS IN THE
MID 20S TO LOWER 30S. VARIABLE WIND TO 10 MPH.
.MONDAY…SNOW LIKELY. SNOW MIXED WITH RAIN ALONG THE COAST IN THE
AFTERNOON. SNOW ACCUMULATIONS 1 TO 4 INCHES. HIGHS IN
THE MID 20S TO LOWER 30S. TURNAGAIN ARM AND PORTAGE VALLEY…EAST
WINDS INCREASING 25 TO 45 MPH IN THE AFTERNOON. ELSEWHERE…NORTH TO
EAST WINDS 15 TO 30 MPH.
.MONDAY NIGHT…SNOW LIKELY. LOWS IN THE UPPER TEENS TO MID 20S.
TURNAGAIN ARM AND PORTAGE VALLEY…EAST WINDS 25 TO 45 MPH.
ELSEWHERE…NORTH TO EAST WINDS 15 TO 30 MPH.
.TUESDAY…SNOW AND RAIN LIKELY. HIGHS IN THE UPPER 20S TO MID
30S. EAST WIND 25 TO 40 MPH.
TEMPERATURE / PRECIPITATION
SEWARD 36 28 30 / 80 40 60
GIRDWOOD 34 26 27 / 80 40 60