Good morning backcountry travelers this is Lisa Portune with the Chugach National Forest Avalanche Information Center on Sunday, January 9th at 7am. 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).
Today the avalanche hazard remains at CONSIDERABLE. The large size of recent human triggered avalanches warrants this elevated danger rating. The 20-30 inches of new snow from last week’s storm fell on an exceptionally weak snowpack littered with multiple layers of buried surface hoar, weak sugary snow, and facets above and below the Thanksgiving Rain Crust (TRC). While natural avalanches are unlikely today, human triggered avalanches still have the potential to go big. The most likely spot to trigger an avalanche today will be in shallow areas of the snowpack where the weak layers are closer to the surface.
You can throw the old “wait 24-hours after a storm and all should be good” rule out the window when you are dealing with persistent weak layers like we have now. Recent large human triggered avalanches happened a full 60-72 hours after the storm. The most recent reported human triggered avalanche happened late Friday afternoon when a skier remotely triggered a medium sized avalanche on Sunnyside just south of the snowmachine uptrack (see photo below). All of these avalanches failed on either buried surface hoar or TRC facets or both.
A few folks inched out onto steeper terrain yesterday and didn’t trigger anything. Tracks on a slope mean nothing right now in terms of stability. It simply means no one found the trigger spot. The human factor is running high with abundant sunshine and powder, so set limits for yourself and stick to them. We should see a gradual increase in stability over time, but I’m still leary of big steep open slopes right now. The trigger spots will be harder to find as the week progresses, but if you do find one, expect a potentially large avalanche. Shallow areas of the snowpack (rocky outcrops) should be avoided like the plague, because that is where you will most likely trigger an avalanche.
Here’s a rundown of recent avalanche activity:
-Large natural avalanches observed on Sunnyside (east aspect), Sunburst (south aspect), Upper Girdwood Valley (south aspect), and Main Bowl (north aspect).
-Skier triggered avalanche on south face of Raggedtop, triggered on buried surface hoar from a chute higher up then propagated down across the face, stepped down to deeper weak layers, crown face 6-8 feet deep at thickest spot.
-Skier triggered avalanche in Warmup Bowl off Seattle Ridge, triggered near some rocks in a shallow area, large propagation across slope, partially buried a snowmachine parked at the bottom of the slope.
-Snowmachiner triggered avalanche on a south facing slope in the Seattle Creek drainage, avalanche released above rider while performing a slope cut.
-Full burial of skier in Palmer Creek drainage near Hope. He was the fourth person to ski the slope but took a steeper line. Skier OK with no injuries.
-Skier remotely triggered an avalanche on east face of Sunnyside near snowmachine uptrack.
-Large avalanche on Widowmaker Peak, Seattle Ridge. Unknown trigger.
Encyclopedia of terms: www.fsavalanche.org/Encyclopedia.aspx
It was anCNFAIC Staff beautiful day in the mountains yesterday…light winds, temps in the 20’s, and abundant sunshine above the low level fog. Our most recent storm that ended 4 days ago dropped 20-30 inches of new snow (2.7” water) over a 5 day period in Turnagain Pass. Skies have been clear since the storm and the winds generally light. A 15 degree temperature inversion exists this morning with Sunburst at 3800′ reading 31F and sea level at 15F. Ridgetop winds are currently light out of the north and skies are clear. Expect more of the same today with stronger winds near Whittier.
I will issue the next advisory tomorrow morning at 7am. If you get out in the backcountry give us a call at 754-2369 or send us your observations using the button at the top of this page. Thanks and have a great day.
The NWS weather forecast for:
WESTERN PRINCE WILLIAM SOUND-
500 AM AKST SUN JAN 9 2011
.TODAY…PARTLY CLOUDY. HIGHS IN THE LOWER 20S TO MID 30S…COOLEST
INLAND. NORTH WIND 15 TO 25 MPH NEAR SEWARD. WEST WIND 20 TO 35 MPH
NEAR WHITTIER. LIGHT WINDS ELSEWHERE.
.TONIGHT…MOSTLY CLEAR. LOWS IN THE MID TEENS TO LOWER 30S. NORTH
WIND 10 TO 20 MPH NEAR SEWARD. WEST WIND 15 TO 25 MPH NEAR WHITTIER.
LIGHT WINDS ELSEWHERE.
.MONDAY…MOSTLY SUNNY. HIGHS IN THE UPPER 20S TO MID 30S. NORTH WIND
10 TO 20 MPH NEAR SEWARD. WEST WIND 15 TO 25 MPH NEAR WHITTIER.
VARIABLE WINDS 10 MPH ELSEWHERE.
TEMPERATURE / PRECIPITATION
SEWARD 29 22 32 / 0 0 0
GIRDWOOD 20 20 32 / 0 0 0
WEATHER STATION SUMMARY for Turnagain Pass:
-3800′ Sunburst Wx Station-
recorded light winds the last 24 hours averaging 5mph out of the west. Temps yesterday ranged from 25F to 30F. The current temp is 31F with light winds out of the north.
-2600′ Seattle Ridge Wx Station-
is not recording winds speeds. Temps yesterday ranged from 20F to 27F. The current temp is 26F.
-1800′ Center Ridge Wx Station-
recorded no new snow the last 4 days. Temps yesterday ranged from 17F to 21F. The current temp is 20F with a total snowpack depth of 69 inches (2 inches of settlement in the last 24 hours).