Good morning backcountry travelers, this is Lisa Portune with the Chugach National Forest Avalanche Information Center on Sunday, February 22, 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 DOT weather station near the crest of the highway in Turnagain Pass at 1000 feet-
is recording a questionable current temp of 26F (5 degrees colder than yesterday) with West winds averaging 3-4 mph.
-The NRCS Center Ridge weather station at 1800 feet in Turnagain Pass-
recorded no new snow. The current temp is 9F (8 degree colder than yesterday) with a total snowpack depth of 68 inches.
-The Sunburst weather station at 3800 feet in Turnagain Pass-
recorded light NW winds averaging 5-10 mph with gusts in the teens during the day yesterday. The current temp is 22F (12 degrees warmer than yesterday)
-General Weather Observations-
This past week 4-6 inches of snow fell in Turnagain Pass and 20-25 inches fell in the upper elevations of the Girdwood Valley. Most of that snow fell last Sunday and was accompanied by gale-force easterly winds. On Friday 2/20 very strong winds predominantly out of the NW, but also observed out of the South and West in Turnagain Pass, sent massive plumes of snow into the stratosphere and affected all elevations from sea level to the ridgetops.
Early this morning, ridgetop temperatures ranged from 18-25 degrees F with light and variable winds. There is currently an inversion with Portage at 5F and Girdwood at 8F. High pressure will keep skies sunny and clear today and tomorrow. Mountain temps will remain in the teens to mid 20’s with patchy fog down low. Winds will be light and variable except closer to the coast where they will blow 10-20 mph out of the NW.
AVALANCHE AND SNOWPACK DISCUSSION
Extra caution is advised again today. CONSIDERABLE avalanche hazard exists at multiple elevations and aspects. Friday’s raging winds formed some stiff, sizeable wind slabs on a variety of leeward aspects. You may find sensitive wind slab near terrain breaks, along the sidewalls of subridges in channeled terrain, under cornices, and on large open slopes. Below 3000 feet on all aspects, weak faceted snow surrounds a thick ice crust now buried 1-2 feet deep in Turnagain Pass and up to 4+ feet deep in the Placer and Girdwood Valleys. This layer was responsible for many natural, skier-, remote-, snowmachine-, and artillery-triggered avalanches this past week.
It has been a pretty active week for avalanche activity to say the least. Human-triggered avalanches occurred as recently as Friday 2/20 in the Skookum Valley, Turnagain Pass, and in the lower Seattle Creek drainage. Natural avalanches occurred as recently as Thursday 2/19 on the flanks of Goat Mountain in the Girdwood Valley. The combination of warm dense windblown snow on top of weak snow on top of slick bed surfaces produced the dangerous avalanche conditions we’ve been seeing this week.
**For a complete rundown of recent avalanche activity check out the photo gallery and the “general snow conditions” at the bottom of this page**
Yesterday my partner and I toured up Tincan and dug a few pits. We found 1-18 inch thick styrofoam-like wind slab and a generally windhammered landscape above treeline. The protected areas below treeline still held some decent powder. I found the January rain crust buried 2 feet deep at 2300 feet. The weak faceted snow on top of the crust still fractured cleanly but it took a bit more force to get it to break. In anCNFAIC Staff snowpit at 2100 feet, I found 12-18 inch thick windslabs that popped off the columns while I was cutting out the back. This is a huge red flag that indicates these recently formed windslabs will easily propagate fractures. Based on these signs of instability and the recent avalanche activity, my partner and I chose to ski low-angled slopes. One of our observers who was also on Tincan reported localized shooting cracks and widespread windslab formation at 2800 feet elevation.
Just a heads up..we received reports of at least five Class 2 skier-triggered soft slab avalanches in Hatcher Pass yesterday on Marmot, Hatch Ridge, and April Bowl. Several folks went for a ride but luckily no one was hurt. One of these slides was 350 feet wide by 600 feet long with a 20-30 inch crown face. We also read on the SnoWest forum that 2 snowmachiners were caught in an avalanche down by Lost Lake on Friday and buried up to their chests. Sounds like no one was hurt but both sleds were buried.
This concludes today’s advisory; the next advisory will be Wednesday, February 25th. 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 FEB 22 2009
.TODAY…PARTLY SUNNY. PATCHY MORNING FOG INLAND. SEWARD AND
WHITTIER…NORTH TO WEST WINDS 10 TO 20 MPH WITH LOCAL GUSTS TO 30
MPH EARLY THIS MORNING. LIGHT WINDS ELSEWHERE. HIGHS IN THE MID 20S
TO LOWER 30S. LIGHT WINDS EXCEPT NORTH 10 TO 20 MPH NEAR SEWARD.
.TONIGHT…MOSTLY CLEAR. LOWS 5 TO 25 ABOVE…COOLEST INLAND.
NORTH TO WEST WINDS 15 MPH ALONG THE COASTS. LIGHT WINDS INLAND.
.MONDAY…PARTLY CLOUDY. HIGHS IN THE LOWER TO MID 30S. LIGHT
.MONDAY NIGHT…MOSTLY CLEAR. LOWS 15 TO 25. VARIABLE WIND TO 10 MPH.
NEAR SEWARD…NORTH WIND 10 MPH.
.TUESDAY…MOSTLY SUNNY IN THE MORNING THEN BECOMING MOSTLY
CLOUDY. HIGHS IN THE 30S. VARIABLE WINDS 15 MPH.
TEMPERATURE / PRECIPITATION
SEWARD 34 20 36 / 0 0 0
GIRDWOOD 30 18 35 / 0 0 0