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In past 24 hours:
The Center Ridge weather station at 1800 feet in Turnagain Pass recorded 11 inches of new snow. Total snowpack depth this morning is 140 inches. The temperature this morning is 27 degrees F (2 degrees colder than yesterday). One week storm totals at Turnagain Pass are: 83 inches or 7 feet.
Sunburst weather station at 3800 feet in Turnagain Pass recorded strong winds averaging 20-30mph out of the NE with gusts up to 60 mph. Temperature this morning is 21 degrees F (2 degrees colder than yesterday). Moderate average NE winds have been recorded at other ridgetop weather stations averaging 20-30 with gusts in the 60’s
Bottom Line (Primary Avalanche Concerns)
The avalanche hazard continues to be very dangerous. Natural and human-triggered avalanches likely. Unstable slabs likely on a variety of aspects and slope angles. Travel in avalanche terrain is not recommended.
1. Another 11-20 inches of snow fell last night. Significant storm snow with strong winds have created more wind slabs
2. This warmer/denser storm snow is sitting on a colder/lighter snow. Plus, a layer of BURIED SURFACE HOAR mixed with facets that formed between Jan 29-Feb10 is on top of that colder/lighter snow in multiple aspects and elevations.
3. Older layers of buried surface hoar that formed in early December-early Janurary are buried deep but could possibly get triggered by very large avalanches stepping down to these older layers.
Avalanche and Snowpack Discussion (More detailed info…)
In the last week we have received nearly 7 feet of snow in Turnagain Pass and nearly 11 feet at Alyeska. Very strong winds have been present in most locations for the duration of the week. We have seen large natural avalanches occur in many areas, in some cases running more than once. With this much wind and snow many starting zones are reloaded again. Unstable conditions have been common from Girdwood Valley to Summit Lake over the past couple days. There have been several very large destructive avalanches observed as recently as yesterday morning.
Here’s a recap of some of the most recent significant avalanches…
-Alyeska triggered a very large avalanche on the North Face that ran all the way to the flats near Winner Creek Trail.
-Alyeska triggered a very large avalanche with artillery on Max’s
-Several very large natural and artillery-triggered avalanches along the Seward Hwy south of Girdwood.
-Chugach Powder Guides reported a very large avalanche triggered by explosives in their snowcat terrain in Girdwood Valley. The crown face was approximately 2 meters deep with large propagation and sympathetic avalanches that wrapped around the majority of the bowl to the North of Notch Ridge.
-Alyeska Resort triggered a very large avalanche off the Headwall with their artillery.
-Avalanche in the Seattle Creek drainage killed two snowmachiners. The large avalanche was triggered by the riders on a steep, windloaded west aspect in an area called Stock Bowl near Widowmaker Peak. Two other riders were dug out successfully by the remaining members of the group. All riders where wearing beacons and had rescue gear. Without the excellent rescue skills of the surviving victims, we would have likely had four fatalities.
-Another very large human-triggered avalanche occurred on Magnum on the same day. Fortunately nobody was caught or injured in this avalanche. It was triggered remotely 50 feet below a skier who was digging a snowpit at the top of the West face above the highway. It propagated thousands of feet down the looker’s left ridge and failed on a “slick layer of facets” 1 meter down.
-Also on Friday, a snowmachiner triggered an avalanche near Skookum Glacier in the Placer drainage and was buried up to his helmet. His partner dug him out uninjured but his sled was buried 7 feet deep.
-Five Fingers path in Portage Valley avalanched large enough to break several trees at the valley floor.
WESTERN PRINCE WILLIAM SOUND-
500 AM AST FRI FEB 22 2008
...STRONG WIND THROUGH THIS MORNING THROUGH PORTAGE VALLEY AND
.TODAY...SNOW AND RAIN SHOWERS. SNOW ACCUMULATION UP TO 3 INCHES.
HIGHS IN THE 30S. LIGHT WINDS. THROUGH PORTAGE VALLEY AND TURNAGAIN
ARM...EAST WIND 20 TO 35 MPH WITH GUSTS TO 50 MPH DIMINISHING TO 10
TO 25 MPH IN THE AFTERNOON.
.TONIGHT...NUMEROUS SNOW SHOWERS. SNOW ACCUMULATION UP TO 2 INCHES.
LOWS IN THE 20S. LIGHT WINDS.
.SATURDAY...MOSTLY CLOUDY WITH ISOLATED SNOW SHOWERS. HIGHS IN THE
UPPER 20S TO MID 30S. LIGHT WINDS.
.SATURDAY NIGHT AND SUNDAY...PARTLY CLOUDY. LOWS 15 TO 25. HIGHS
IN THE MID 20S TO LOWER 30S. LIGHT WINDS.
.SUNDAY NIGHT...PARTLY CLOUDY. LOWS 10 TO 25.
TEMPERATURE / PRECIPITATION
SEWARD 36 26 33 / 80 60 20
GIRDWOOD 36 21 30 / 80 60 20
Let us know if you see or hear of any avalanche activity. You can leave a message at 754-2369 or email us by going to our home page at avalanche.org. The next advisory will be on Saturday, February 23rd.
Wednesday, February 20, 2008
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