Good Morning backcountry travelers, this is Matt Murphy with the Chugach National Forest Avalanche Information Center on Friday, March 6, 2009 at 7am. This will serve as a general backcountry avalanche advisory issued 5 days a week Wednesday-Sunday for the Turnagain Arm area(Turnagain Pass is the core advisory area). Local variations always occur. This advisory expires in 24 hours and does not apply to operating ski resorts or highways/railroads.
MOUNTAIN WEATHER ROUND UP FOR THE LAST 24 HOURS
-General Weather Observations-
The SNOTEL sites from Summit, Grandview, Turnagain Pass: recorded 0.1-0.3 inches of water and 1-3 inches of new snow. Winds have been light to moderate, but have been increasing at ridgetops this morning gusting up to 34mph. Temps are colder at all weather stations from Summit Lake to Turnagain Arm by 2-7 degrees.
–The DOT weather station near the crest the highway at Turnagain Pass at 1000 feet–
Is acting strange
–The NRCS Center Ridge weather station at 1800 feet in Turnagain Pass–
Has a temp of 20 degrees (3 degrees colder than yesterday). 0.1 inches water and 1-2 inches of new snow has been recorded. Total snowpack depth is 71″.
–The Sunburst weather station at 3800 feet in Turnagain Pass–
Has not recorded any info since 10pm last night….Let’s look at Mile 43 Peak at 3300 along the railroad tracks near Grandview instead.
It shows a temperature of 13 degrees (7 degrees colder than yesterday). Winds have been calm to moderate averaging 1-14 mph from the SW with a max gust of 34mph. Winds have been increasing in the past couple hours.
-Surface Analysis Maps-
Between 3am and 9pm yesterday….Show the storm we have been watching for the past couple days moved way up north and its outer arm of precip has moved past us. There is a high pressure building in strength (1036-1043mb) as it moves right toward us. Plus, there is anCNFAIC Staff decent looking storm lurking out past the Aluetians.
Show scattered precip over the Kenai Peninsula, but it looks like clear weather just to our west.
Primary avalanche concerns
-Below 3000 feet. Rain crust buried under 1-4 feet of surface snow. There is a layer of weak sugary faceted snow on top and below this hard rain crust. We are still finding moderate to hard instability on top of this crust in our stability tests. This crust is showing signs of being a very persistent weak layer.
-Above 3000 feet. Variable pockets of instability. Yeah, I know…Thats pretty generic, but we have had a report of a human-triggered class 2 slab up high. Plus, we’ve been finding a clean shear about 1-2 feet deep.
-Sea-level to at least 3200′ (Probably higher). New eggshell crust was observed in Girdwood and Turnagain Pass on 3/5/09. It was everywhere on all aspects and could become very dangerous if it gets buried with more than 1 foot of slaby snow.
AVALANCHES AND SNOWPACK
Elevated Caution is advised today due to new windslabs on top of that eggshell crust. Plus that clean shear we’ve been seeing in top 1-2 feet of snow above 3000 feet might be more reactive on slopes steeper than 35 degrees today due to yesterday’s new snow and this morning’s increasing wind. The rain crust below 3000 feet is not likely to avalanche right now but it is still a serious concern and has the most potential for large avalanches. A big red flag for this lower elevation weak layer will be rain on the snow.
That new eggshell crust that formed on the surface Wednesday night 3/4/09 makes me nervous. If that crust gets buried with enough snow, it could become a very dangerous bed surface. We did not get very much snow yesterday to make me really nervous, but watch out for wind slabs with today’s forecasted strong winds. Today’s wind slabs will probably be small be very reactive.
That clean shear up high that we have been observing in the top 1-2 feet of snow that sometimes has been identified as buried surface hoar has more potential for problems today. This layer should heal up fairly fast, but it might have more life to it today due to the new snow and wind.
This is NOT one of those times when you can wildly attack the mountains and its not a good time to do anything radical either. Strict adhearance to travel rituals are the key to staying safe. Skiing one at a time, watching your partners, and staying spaced out are some of the strategies that will help keep you and your friends alive. Bring your inclometer. If you are on slopes steeper than 35 degrees, then you are in terrain that has the most potential for triggering one of those landmines.
Down low (below 3000 feet), That sugary faceted snow (mixed forms) on top of that rain crust is still a problem that is not showing signs of going away. We will see avalanches on this weak layer before the season is done. Watch out if it rains at these lower elevations.
WESTERN PRINCE WILLIAM SOUND-
500 AM AKST FRI MAR 6 2009
…STRONG WIND THROUGH EARLY SATURDAY MORNING IN SEWARD AND
.TODAY…MOSTLY SUNNY. HIGHS IN THE MID 20S TO LOWER 30S. NORTH
TO WEST WIND 15 TO 25 MPH WITH GUSTS TO 35 MPH. GUSTS TO 50 MPH
IN SEWARD AND WHITTIER.
.TONIGHT…MOSTLY CLEAR. LOWS ZERO TO 20 ABOVE…COLDEST INLAND.
NORTH TO WEST WIND 15 TO 30 MPH…DIMINISHING OVERNIGHT. GUSTS
TO 50 MPH IN SEWARD AND WHITTIER.
.SATURDAY…MOSTLY SUNNY. HIGHS 15 TO 25. NORTH TO WEST WIND
TO 15 MPH. GUSTS TO 35 MPH IN SEWARD AND WHITTIER IN THE MORNING.
.SATURDAY NIGHT…PARTLY CLOUDY IN THE EVENING THEN BECOMING
MOSTLY CLOUDY. LOWS ZERO TO 15 ABOVE…COLDEST INLAND. NORTH
TO WEST WIND 10 TO 15 MPH IN THE EVENING BECOMING LIGHT.
TEMPERATURE / PRECIPITATION
SEWARD 32 18 27 / 0 0 0
GIRDWOOD 30 12 22 / 0 0 0
This concludes today’s avalanche advisory and it will expire in 24 hours. The next advisory will be on Saturday, March 7th. Thanks and have a great day.