Good Morning backcountry travelers, this is Carl Skustad with the Chugach National Forest Avalanche Information Center on Saturday, February 28, 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 does not apply to operating ski resorts or highways/railroads.
MOUNTAIN WEATHER ROUND UP FOR THE LAST 24 HOURS
-General Weather Observations-
Light snow is still falling this morning in most of Southcentral. 2-3 inches at Summit Lake, 1 inch in Turnagain, 2 inches in Girdwood, 1 inch on the Upper Hillside, and 4-6 potential inches recorded in Hatcher. Although outside our advisory area , Hatcher Pass… has seen natural and human triggered avalanches in the last 7 days. Some of these are large and very hazardouse. Look for this precipitation band to move through the area this morning. Scattered clouds and showers will ride it’s wake.
–The DOT weather station near the crest the highway at Turnagain Pass at 1000 feet–
Is recording scetchy temperatures and I’m not buying it! Winds are light, 3-4 mph out of the NE.
–The NRCS Center Ridge weather station at 1800 feet in Turnagain Pass–
Has a temp of 20 degrees (4 degrees warmer than yesterday). .1 – .2 inches water and a possible inch of new snow. Total snowpack depth is still 67″.
–The Sunburst weather station at 3800 feet in Turnagain Pass–
Shows a temperature of 13 degrees (3 degrees warmer than yesterday). Southwest winds are increasing averaging 15-17 mph with gust in the 20’s.
-Surface Analysis Maps-
A 1020 mb low is curently over the area.
The Kenai radar shows a nice band of precipitation over the area from Kenai to the Mat Valley. This system is fast moving and should pass by mid morning. The Prince William Sound Middleton Radar is covered with precip that is heading to Valdez and Cordova. They get all the love!
Primary avalanche concerns
-Above 3000 feet. Hard wind slabs. Multiple density layers/interfaces in the top 1-2 feet of snow with potential for human-triggered avalanches.
-Below 3000 feet. Rain crust buried under 1-4 feet of surface snow. Avalanches have been common and widespread on this lower elevation instability. There is a layer of faceted snow on both sides of this crust. Be very careful on steep slopes in Lost Lake, Placer Valley, Seattle Creek, and Girdwood Valley. This weak layer will be a problem for some time!
AVALANCHES AND SNOWPACK
Elevated Caution is still advised. The danger rating is MODERATE. Natural avalanches unlikely. Human triggered avalanches possible today.
Not much change from yesterday, CNFAIC Staff than this light smattering of new snow. We still have some questions about the current stability of our snowpack. In general our stability has improved over the last week but by no means are we out of the woods. We will have a tricky snowpack the rest of the season. We need additional observations to increase our advisory accuracy, so if your out and about let us know what you find.
Climbing in Turnagain Pass this week we found a grab bag of wind slab layers. Last Friday’s wind event really hammered much of the snowpack from Girdwood to Summit Lake. In many areas these wind slabs are very sensitive but very small, measuring only a couple of inches. Near the ridge tops these wind slabs are much thicker and stiffer, measuring 1-2 feet. We found very easy failures on the smaller slabs, (CT1 Q2 (x2)). 1 to 1.5 feet deep we found harder test results (CT24,25 Q2). The surface varies from boiler plate to sastrugi (see photo).
Sunburst Ridge- Sastrugi is the name we give the snow surface after it has been eroded by strong winds.
The main problem with upper elevations today relates to the tricky nature of hard slabs. It’s common for people to get way out in the middle of a hard slab before it avalanches. The photo gallery has a photo of a small hard slab avalanche that was skier triggered while skinning up Lipps last Saturday.
-That rain crust below 3000 feet continues to be a problem. One of our observers found that rain crust Tuesday on the Sunnyside of Turnagain Pass (climbers left of Repeat Offender). In his extended column test, he found propogation across the entire column with a very clean and fast Q1/Q2 shear. Q1 represents the quality or cleaness that one snow layer has when is breaks free from the layer below it. Q1’s indicates a problematic energy in the snowpack. Anytime you see super fast clean shears, you should stay away from those slopes. AnCNFAIC Staff observation came from Eddy’s on Wed. He found buried surface hoar at 2500 ft. This is a serious concern because we have found this layer in some snow pits and not in CNFAIC Staffs, providing much spacial variability to our snowpack. Buried surface hoar is a very sneaky layer and is hard to find but when it’s present,it’s a notorious weak layer. It’s a weak layer responsible for many fatalities.
Safe terrain management and strict travel rituals are still essential right now.
WESTERN PRINCE WILLIAM SOUND-
500 AM AKST SAT FEB 28 2009
.TODAY…SNOW. SNOW ACCUMULATION 2 TO 4 INCHES. HIGHS IN THE
UPPER 20S TO MID 30S. VARIABLE WIND TO 10 MPH.
.TONIGHT…MOSTLY CLOUDY. SCATTERED SNOW SHOWERS IN THE EVENING.
LOWS IN THE MID TEENS TO LOWER 20S. NORTH AND WEST WIND 10 TO 20 MPH.
STRONGER WINDS TO 35 MPH NEAR SEWARD AND WHITTIER AFTER MIDNIGHT.
.SUNDAY…DECREASING CLOUDS. HIGHS IN THE 20S. NORTH AND WEST WIND 10
TO 20 MPH. STRONGER WIND 25 TO 35 MPH NEAR SEWARD AND WHITTIER.
.SUNDAY NIGHT…MOSTLY CLEAR. LOWS 5 TO 15 ABOVE. NORTH AND WEST WIND
10 TO 15 MPH. STRONGER WIND TO 30 MPH NEAR SEWARD AND WHITTIER
DECREASING TO 15 MPH AFTER MIDNIGHT.
.MONDAY…INCREASING CLOUDS. HIGHS IN THE 20S. VARIABLE WIND TO 10
TEMPERATURE / PRECIPITATION
SEWARD 32 23 27 / 80 40 0
GIRDWOOD 30 21 25 / 100 40 0
This concludes today’s avalanche advisory the next advisory will be on Sunday, February 29th. Thanks and have a great day.