Good morning backcountry travelers, this is Carl Skustad with the Chugach National Forest Avalanche Information Center on Friday, December 5, 2008 at 7am. This will serve as a general backcountry avalanche advisory issued for the Turnagain Arm. 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 a trace of new snow yesterday morning. Current temperature is 33 degrees F (5 degrees warmer than yesterday morning). Total snowpack depth is 48 inches.
-Sunburst weather station at 3800 feet in Turnagain Pass-
This station will be giving us trouble until we get a new battery up to this remote site. As of 0300 this morning this station had 27 deg F, 13 mph winds out of the east with gust in the 20’s
-Max’s weather station at 3200 feet in Girdwood Valley-
Recorded light to moderate winds averaging 8-19 mph and 31deg F.
-Surface Analysis Maps-
Shows a weak low (1005mb) pushing into the gulf with two high pressure systems behind it for early next week.
The Middleton radar shows a wall of light to moderate precip hitting the outer coast of the Kenai from Seward to Whittier. The Kenai radar shows a wall of light to moderate precip over the western cook inlet.
The main flow has shifted away from us to the south east.
-General Weather Observations-
All the temperatures are up again this morning. Most areas are above the freezing point. The weather challenge today will be if precip falls as rain or snow. We might see the snow line creep up a little more!
PRIMARY AVALANCHE CONCERNS
-Wind slabs of deeper dense snow on top of shallow weaker less dense snow
-buried surface hoar (about 3 feet deep)
-Rapid loading of any kind (precip, wind, temperature)
AVALANCHE AND SNOWPACK DISCUSSION
Yesterday, Matt and I climbed up the Sunnyside (top of Seattle Ridge) of T-Pass to investigate a week old avalanche the snowmachineres triggerd last Friday. As we suspected this large avalanche failed on top of the weak faceted October snow near the ground. We continue to get fairly stable test results in our snow pits (CT30+Q2101cm) but we can’t trust these tests 100%. What they do tell us is that these layers are on the mend. In most places we will not have enough of an impact with our snowboard, snowmachine , or ski, to trigger an avalanche. Places to still wake the avalanche dragon exist near areas of thinner snow like rock bands, alder clumps, and scoured ridges. This has been the case in many close calls including last years large avalanche on Sunburst and this Thanksgiving day avalanche in Bear Valley on the upper Hillside. If an avalanche is triggered it could propagate into deeper snow and grow in size very quickly. AKDOT/AKRR triggered just such an avalanche yesterday with artillery near Kern Creek that covered the tracks (see photo album).
The bottom line is we have a 3-6 foot dense slab on top of weaker unconsolidated snow in many places. We have not received enough snow or water load to trigger these slabs. Each storm pushes us closer to the trigger point. This point is reached when the stress of the snowpack exceeds the strength of the weak layer. Any sudden change in weather will increase the avalanche hazard quickly. Wind, snow, or more importantly today rain could be enough stress on the snowpack.
Out of Advisory Area Note: AnCNFAIC Staff skier triggered avalanche in South Fork area of Eagle River yesterday. A skier remotely triggered a 16-20 inch avalanche, 400 feet above them. It measured approx. 400 ft wide and ran 700 ft. In addition Chugach State Park Rangers (snow ninjas Thomas and Wedeking) reported wind slabs over faceted weak snow in much of the State Park. Natural avalanche activity was reported mid week on Power Line trail.
WATCH OUT SITUATIONS
-collapsing or “whoomping”. If you feel or hear any of this, then get to safe terrain immediately and call it a day.
-rapid loading. The weather forecast below does not sound like anything too serious, but we need to be ready for the next big dump.
WESTERN PRINCE WILLIAM SOUND-
500 AM AKST FRI DEC 5 2008
.TODAY…RAIN SHOWERS NEAR THE COAST AND SNOW SHOWERS INLAND. SNOW
ACCUMULATION UP TO 1 INCH. HIGHS IN THE 30S. EAST WIND 10 TO 15 MPH.
GUSTS TO 25 MPH THROUGH TURNAGAIN ARM DURING THE MORNING.
.TONIGHT…SNOW AND RAIN. SNOW ACCUMULATION UP TO 3 INCHES. LOWS IN
THE MID 20S TO LOWER 30S. EAST WIND 10 TO 15 MPH.
.SATURDAY…SNOW AND RAIN LIKELY. SNOW ACCUMULATION UP TO 2 INCHES.
HIGHS IN THE 30S. VARIABLE WIND TO 10 MPH.
.SATURDAY NIGHT…SNOW AND RAIN LIKELY. LOWS IN THE MID 20S TO
LOWER 30S. LIGHT WINDS.
.SUNDAY…SNOW LIKELY. HIGHS IN THE 30S. LIGHT WINDS.
.SUNDAY NIGHT…MOSTLY CLOUDY WITH SCATTERED SNOW SHOWERS. LOWS
IN THE MID 20S TO LOWER 30S.
.MONDAY…MOSTLY CLOUDY WITH A CHANCE OF SNOW. HIGHS IN THE MID
20S TO LOWER 30S.
TEMPERATURE / PRECIPITATION
SEWARD 37 30 38 / 80 80 60
GIRDWOOD 35 27 33 / 60 80 60
This concludes todays advisory, the next advisory will be on Saturday the 6th, thanks and have a great day!