Good morning backcountry travelers, this is Lisa Portune with the Chugach National Forest Avalanche Information Center on Sunday, January 25, 2008 at 7am. This will serve as a general backcountry avalanche advisory issued 5 days a week Wednesday through 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…
-The Center Ridge weather station at 1800 feet in Turnagain Pass recorded 3 inches of new snow and 0.2 inches of water. The current temperature is 26 degrees F (2 degrees warmer than yesterday).
-The Sunburst weather station at 3800 feet in Turnagain Pass and Max’s weather station at 3200 feet in the Girdwood Valley both recorded light easterly winds averaging 5-10 mph with gusts in the teens and 20’s. We did, however, see plumes of snow on the ridgetops yesterday at the south end of the pass near Superbowl Peak. The Sunburst station went offline at 2am and was averaging 13mph at the time. Mountain winds at all CNFAIC Staff stations are currently light out of the East with ridgetop temps ranging from 20-22 degrees F.
It was a quiet week weather-wise with just 6-12” of new snow accumulation spread out over the week accompanied by light to moderate easterly winds and a few strong gusts on Thursday and Friday. Expect maybe anCNFAIC Staff inch of snow today with light easterly winds to 15 mph and mountain temps in the 20’s. Lingering snow showers will taper off this evening and the winds will slightly increase and shift direction by tomorrow night, blowing 10-20 mph out of the NW. Temps will gradually decrease the next few days as skies clear.
1. A weak layer of sugary faceted snow that formed during our cold snap is now buried under 2-6 feet of warm dense snow. Although the probability is low, avalanches triggered on this layer, or stepping down to this layer, will be large and destructive.
2. Pockets of sensitive windslab may exist at the higher elevations on leeward aspects near ridgetops, under cornices, and along the sidewalls of subridges in channeled terrain.
AVALANCHE AND SNOWPACK DISCUSSION
Folks are slowly inching back into bigger terrain and finding great snow conditions at higher elevations. Rain runnels and breakable crust still exist below 1500 feet, but the fresh snow on top certainly improved skiing and riding conditions. It has been over a week since any natural or human-triggered avalanches, and all signs point to stable conditions; HOWEVER, it is difficult to have complete confidence when the snowpack includes two significant buried weak layers of sugary facets: the October facets near the ground and the January facets midpack. Right now we are most concerned with the January facets buried 2-6 feet deep.
Ben and I toured up Cornbiscuit yesterday and checked out a north aspect where we found the January facets buried only a foot below the surface. They looked to be rounding out and the shears on this layer were uneven and irregular Q3’s, which is a good thing in terms of stability. We were, however, able to get the October facets to cleanly fracture, but only after pounding on the shovel. I can see how a large enough trigger, like the natural avalanche that happened on Magnum last Friday, could cause this bottom layer of facets to fail and rip out to the ground.
Deep slab instabilities do exist at the higher elevations above 2800 feet where temps are colder and the facets remain weak and sugary. The chance certainly remains of triggering a deep slab avalanche in thin, rocky starting zones in these higher elevations. Remember that tracks on a slope do not mean the slope is stable, especially when you are dealing with deep slab instabilities.
Two of our observers reported a cornice break on Sunburst 2 days ago that was a little more sensitive than they expected. As Ben approached the spot where he was going to kick off the cornice to test the slope, the cornice suddenly broke in front of him and fractured 50 feet wide.
This concludes today’s advisory; the next advisory will be Wednesday, January 28th. If you are out in the backcountry and have the chance, please send us your observations. Simply click on “Submit a snow observation online” at the top of the advisory page and fill in the blanks. Thanks and have a great day!
The weather forecast for:
WESTERN PRINCE WILLIAM SOUND-
500 AM AKST SUN JAN 25 2009
.TODAY…SNOW…MAINLY ALONG THE SOUND. SNOW ACCUMULATION UP TO
1 INCH INLAND AND 2 TO 5 INCHES ALONG THE SOUND. HIGHS IN THE
UPPER 20S TO MID 30S. NORTH TO EAST WIND TO 15 MPH.
.TONIGHT…CLOUDY. SNOW SHOWERS ALONG THE SOUND. SNOW ACCUMULATION
1 TO 3 INCHES. LOWS IN THE 20S. NORTH TO EAST WIND TO 15 MPH.
.MONDAY…MOSTLY CLOUDY. SCATTERED SNOW SHOWERS ALONG THE COAST
IN THE MORNING. HIGHS IN THE MID 20S TO LOWER 30S. NORTH TO WEST
WIND TO 15 MPH. GUSTS TO 25 MPH NEAR SEWARD.
.MONDAY NIGHT…PARTLY CLOUDY. LOWS 15 TO 25. NORTH TO WEST WIND
10 TO 20 MPH WITH GUSTS TO 40 MPH NEAR SEWARD AND WHITTIER.
.TUESDAY…MOSTLY SUNNY IN THE MORNING THEN BECOMING MOSTLY CLOUDY.
HIGHS IN THE 20S. NORTH TO WEST WIND TO 15 MPH. GUSTS TO 30 MPH
NEAR SEWARD AND WHITTIER IN THE MORNING.
TEMPERATURE / PRECIPITATION
SEWARD 32 27 30 / 20 0 20
GIRDWOOD 33 25 27 / 80 20 0