Good Morning backcountry travelers, this is Matt Murphy with the Chugach National Forest Avalanche Information Center on Thursday, March 5, 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-
Once again, nothing too drastic happened. A couple of inches of snow fell around our area. The SNOTEL sites from Summit, Grandview, Turnagain Pass: recorded 0.1-0.3 inches of water and 1-2 inches of new snow. Winds have been light to moderate. Temps are warmer at all weather stations from Summit Lake to Turnagain Arm except 1-2 degrees colder on the ridges at Sunburst and 43 Mile Peak.
–The DOT weather station near the crest the highway at Turnagain Pass at 1000 feet–
Is recording what looks like a false temp of 40 degrees, but it still shows a trend of (6 degrees warmer than yesterday) and 1-2 inches of new snow.
–The NRCS Center Ridge weather station at 1800 feet in Turnagain Pass–
Has a temp of 23 degrees (12 degrees warmer than yesterday). .1-.2 inches water and 1 inch of new snow has been recorded. Total snowpack depth is 69″.
–The Sunburst weather station at 3800 feet in Turnagain Pass–
Shows a temperature of 18 degrees (1 degree colder than yesterday). Winds have been calm to moderate averaging 4-13 mph from the SE with a max gust of 19mph.
-Surface Analysis Maps-
Between 3am and 9pm yesterday….Show that same storm from yesterday. It gained strength (977-974mb) as it moved NE accross the Bering Sea, and continued to pull an arm of moisture up from the south.
That arm of moisture shows up on the satellite, but there is nothing on the radars. Either way, that arm is to our west; so, it does not appear that it will bring very much precip toward us. That seems to jive with the NOAA forecast of anCNFAIC Staff .1-.25 inches of precip for our area today.
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.
AVALANCHES AND SNOWPACK
Normal Caution is advised on most slopes less than 35 degrees, but there are some pockets of moderate avalanche hazard. 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 clean shear we’ve been seeing in the surface snow above 3000 feet might be more reactive on slopes steeper than 35 degrees today due to yesterday’s new snow and a little wind.
We are being haunted with the dreaded “isolated pockets of instability” right now. Its unlikely to trigger a huge avalanche today, but it is possible to trigger a small one. Remember that it does not take much to bury you. That clean shear up high that sometimes has been identified as buried surface hoar has the most potential for problems today. This layer should heal up fairly fast, but it might have more life to it today due to a little 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 inclinometer. 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 THU MAR 5 2009
.TODAY…PERIODS OF SNOW AND ISOLATED AREAS OF FREEZING RAIN IN THE
MORNING. RAIN AND SNOW LIKELY IN THE AFTERNOON. SNOW ACCUMULATION 1
TO 3 INCHES. HIGHS IN THE 30S. SOUTHEAST WIND 10 TO 20 MPH EXCEPT
SOUTHEAST 15 TO 30 MPH THROUGH PORTAGE VALLEY AND TURNAGAIN ARM.
.TONIGHT…MOSTLY CLOUDY. A CHANCE OF SNOW IN THE EVENING…THEN
SCATTERED SNOW SHOWERS AFTER MIDNIGHT. LOWS IN THE 20S. WEST WIND
10 TO 20 MPH.
.FRIDAY…MOSTLY CLOUDY WITH ISOLATED SNOW SHOWERS IN THE
MORNING…THEN PARTLY CLOUDY IN THE AFTERNOON. HIGHS IN THE UPPER
20S TO UPPER 30S. NORTHWEST WIND 15 TO 30 MPH.
TEMPERATURE / PRECIPITATION
SEWARD 37 28 38 / 80 40 0
GIRDWOOD 35 22 31 / 100 60 20
This concludes today’s avalanche advisory and it will expire in 24 hours. The next advisory will be on Friday, March 6th. Thanks and have a great day.