Good morning backcountry travelers this is Carl Skustad with the Chugach National Forest Avalanche Information Center on Friday March 26th, 2010 at 7 am. This will serve as a general backcountry avalanche advisory issued for Turnagain Arm with Turnagain Pass as the core advisory area (this advisory does not apply to highways, railroads, or operating ski areas).
This week is Telepalooza week at Alyeska Resort. There are lots of great events and a fundraiser for the Friends of the Chugach National Forest Avalanche Information Center. Check Alyeska Resort’s webpage or www.telepalooza.com for a detailed schedule of events.
Skies cleared yesterday for a pleasant day of World Comp riding and skiing at Alyeska. The east to southerly winds diminished into the teens, then single digits this morning. Temperatures reached the mid 30’s at mid elevations while alpine temperatures stayed below freezing. The radars are clear this morning. The satellite images indicate clouds moving into the area by mid day. A 968 mb low is riding the jet just to our south. Short wave activity off this low will provide a good chance of precip this evening and tomorrow.
Today’s avalanche danger is MODERATE. Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully. Natural avalanches unlikely; human triggered avalanches possible.
We have multiple weak layers in the upper 3 feet of our snowpack. These layers consist of surface hoar on all aspects, and suncrusts on southerly aspects.
We received reports of skier triggered avalanche activity yesterday near Sunburst, Magnum, and Lynx Creek Areas. All reported avalanches were small to medium in nature, breaking 6-26 inches deep. Aspects ranged from south to northeast. Stability tests indicate variable weak layers in this 2-26 inches depth range.
Likely areas to trigger avalanches today include: steep hanging alpine snowfields near ridgetops and steep convex rollovers. If the clouds stay away and the sun intensifies in the afternoon, southerly aspects will also see an increased chance of avalanche activity.
There are three main problem layers in the snowpack right now:
1. A sun crust with surface hoar on top of this crust is now buried under Tuesday’s new 4-6 inches of new snow. We observed surface hoar on top of this crust in multiple locations. This layer could create small human-triggered avalanches on steep slopes where wind has deposited deeper snow.
2. A sun crust that is buried 2-3 feet deep (we have observed surface hoar near this crust) We have been finding moderate to hard failures with smooth shear planes on top and underneath this crust. It might become more reactive with a heavier load on top of it, or small avalanches might step down to this layer making medium sized avalanches.
3. Multiple layers of buried surface hoar in the top 1-3 feet of snow
There is a lot of spatial variability in the snowpack right now including multiple layers of buried surface hoar and buried suncrusts in the top 3 feet of snow. At lower elevations, there is a 1 inch thick breakable crust on all aspects up to about 1500-2000′ which is now buried under 4-6 inches of wet snow. Mid elevations to ridge top elevations generally have multiple buried suncrusts on southern aspects, but these crusts are very aspect-dependent and do not wrap around to CNFAIC Staff aspects. The uppermost suncrust was thin but it had surface hoar on top of it. Northern aspects at Turnagain Pass are generally thin, cold, and faceted especially in rocky areas.
Glide cracks are secondary concern today. These crevasse like features are those cracks that go all the way to the ground. One of these glide cracks avalanched on Friday or Saturday on the southern aspect of Tincan to the lookers left of Tincan Proper (see photo gallery).
WEATHER FORECAST (National Weather Service)
WESTERN PRINCE WILLIAM SOUND-
500 AM AKDT FRI MAR 26 2010
.TODAY…MOSTLY SUNNY IN THE MORNING THEN BECOMING PARTLY CLOUDY.
HIGHS IN THE UPPER 30S. VARIABLE WIND 10 MPH EXCEPT NORTH WIND
10 TO 15 MPH NEAR SEWARD.
.TONIGHT…A SLIGHT CHANCE OF SNOW SHOWERS IN THE EVENING…THEN
SNOW AFTER MIDNIGHT. SNOW ACCUMULATION UP TO 2 INCHES. LOWS IN
THE MID 20S TO LOWER 30S. NORTH TO EAST WIND TO 15 MPH EXCEPT
NORTH WIND 15 TO 25 MPH NEAR SEWARD.
.SATURDAY…RAIN AND SNOW IN THE MORNING…THEN RAIN IN THE
AFTERNOON. UP TO 1 INCH WET SNOW ACCUMULATION THROUGH TURNAGAIN
PASS. HIGHS IN THE UPPER 30S TO MID 40S. NORTH TO EAST WIND
10 TO 15 MPH INCREASING TO 15 TO 30 MPH IN THE AFTERNOON.
.SATURDAY NIGHT…RAIN AND SNOW. LOWS IN THE 30S. EAST WIND
15 TO 30 MPH WITH GUSTS TO 40 MPH THROUGH PORTAGE VALLEY AND
.SUNDAY…RAIN LIKELY. HIGHS IN THE LOWER TO MID 40S.
EAST WIND 10 TO 25 MPH.
TEMPERATURE / PRECIPITATION
SEWARD 39 32 41 / 0 80 80
GIRDWOOD 38 30 40 / 0 80 80
WEATHER STATION SUMMARY for last 24 hours at TURNAGAIN PASS
3800′-Sunburst Wx Station
Temp (5am): 18 (1 degrees colder than yesterday morning)
Winds: In last 24 hours winds have been light to moderate averaging 4-15 mph
HIGH TEMP 23 at 6pm
2600′-Seattle Ridge Wx Station
Temp (5am): 19 (4 degrees colder than yesterday morning)
Winds: In last 24 hours winds have been light to moderate averaging 3-21 mph
HIGH TEMP 22 at 2pm
1800′-Center Ridge Wx Station
Temp (5am): 20 (6 degrees colder than yesterday morning)
HIGH TEMP 41 at 2 pm
Thanks for checking today’s avalanche advisory. I will update this advisory tomorrow morning by 0700. Thanks and have a great day.