Good morning backcountry travelers, this is Carl Skustad with the Chugach National Forest Avalanche Information Center on Friday, December 12, 2008 at 7am. This will serve as a general backcountry avalanche advisory issued for the Turnagain Arm Area (Turnagain Pass is the core advisory area). Local variations always occur.
INTERAGENCY AVALANCHE RESCUE TRAINING
On the weekend of December 13-14, there will be an avalanche rescue training taking place this weekend at Turnagain Pass. Please be aware of rescue workers, helicopters, rescue snowmachines and areas set up for rescue training drills. Thanks.
MOUNTAIN WEATHER ROUND UP
In the last 24 hours…
-The Center Ridge weather station at 1800 feet in Turnagain Pass-
Recorded no new snow. Current temperature is 7 degrees F (9 degrees colder than yesterday morning). Total snowpack depth is 62 inches, with a total of 7 inches of settlement since the storms end Wed.
-Sunburst weather station at 3800 feet in Turnagain Pass-
Recorded moderate NW winds averaging 10-14 mph. Current temperature is 7 degrees F (4 degrees colder than yesterday)
-Surface Analysis Maps-
the remnants of the storm are petering out as a weak low pressure (1022 mb) system passes through today, then two high pressure systems are on tap for the weekend.
The analysis from 9pm last night showed the main flow streaming from west to east and heading right towards Juneau. The forecast predicts shift in the next 24 hours and start flowing from north to south.
-General Weather Observations-
Burr, Summit lake is the cold spot this morning with -1 deg. mercury. All CNFAIC Staff stations are in the single digits as well except for Portage (19). Expect ridge top winds today in the teens. Wind direction will prevail out of the NW but will be channeled by local topography.
PRIMARY AVALANCHE CONCERNS
AVALANCHE AND SNOWPACK DISCUSSION
A snowmachine triggered avalanche in either Mama’s or Main bowl yesterday (see our map page for location). The rider went for a ~500 foot ride while his sled stayed up on the crown. Not a lot of info on this but he was buried up to his chest after deploying his ABS airbag backpack. If you were involved with this ride please contact us. Glad everyone was alright. Don’t count on the technology to save your butt every time. Get educated and make good decisions. Managing terrain will be the name of the game this weekend. There will be clear skies and lots of blower powder. The avalanche I just described failed 2 feet deep. This is new storm snow on old snow. Matt and I tested this interface yesterday on Sunburst and found moderate to hard test results. CT22 Q2 70cm. This type of weak layer will tighten up over the next couple of days, but obviously still has potential to take you for a ride. Alex found less new snow at Summit Lake but weaker snow stability scores. I expect Summit and Lost Lake to have a slightly higher avalanche hazard than Turnagain this weekend, do to a shallower snowpack and windier conditions leading to wind slab formations on southern and eastern aspects. We also found the buried layer of surface hoar 5 feet deep. You can still see it with the naked eye, but test resulted in hard sheers. CT30+ Q2 160cm
Here’s the facts…
-Those week October facets failed on multiple aspects during this past storm.
-Big terrain with large bowls near wind scoured ridges seemed to produce the largest avalanches.
-Artillery was able to trigger some large avalanches yesterday afternoon.
-The snowpack has settle 7 inches in the past 48 hours, temps have cooled down, winds have been moderate.
Matt, asked the question yesterday “can we still humanly trigger avalanches”, the answer is yes. You can still find the avalanche dragon lurking on actively loading leeward slopes, in shallower snow near rock bands and on scoured ridges. Keep your slope angles less than 38 deg and reduce exposure to complex terrain and you can enjoy great blower powder.
WATCH OUT SITUATIONS
-Rocky terrain with shallow snow connected to deeper snow
-Steep rollovers (check out the photo gallery picture of Mangum)
WESTERN PRINCE WILLIAM SOUND-
500 AM AKST FRI DEC 12 2008
.TODAY…MOSTLY SUNNY IN THE MORNING THEN BECOMING MOSTLY CLOUDY.
HIGHS IN THE MID TEENS TO LOWER 20S. NORTH AND WEST WIND 10 TO 20 MPH
WITH GUSTS TO 35 MPH NEAR WHITTIER AND SEWARD.
.TONIGHT…DECREASING CLOUDS. LOWS 5 TO 15 ABOVE. NORTH AND WEST WIND
10 TO 25 MPH WITH GUSTS 35 MPH NEAR WHITTIER AND SEWARD.
.SATURDAY…SUNNY. HIGHS IN THE MID TEENS TO LOWER 20S. NORTHWEST
WIND 10 TO 20 MPH. GUSTS TO 35 NEAR WHITTIER AND SEWARD DIMINISHING
IN THE AFTERNOON.
.SATURDAY NIGHT…MOSTLY CLEAR. LOWS 5 TO 15 ABOVE. NORTH WIND
.SUNDAY…SUNNY. HIGHS IN THE UPPER TEENS TO MID 20S. LIGHT
.SUNDAY NIGHT…MOSTLY CLEAR. LOWS IN THE TEENS.
TEMPERATURE / PRECIPITATION
SEWARD 23 17 27 / 0 0 0
GIRDWOOD 18 5 16 / 0 0 0