Good morning backcountry travelers this is Jon Gellings with the Chugach National Forest Avalanche Information Center on Wednesday, January 12th 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).
A huge thanks goes out to everyone who submitted observations this past weekend! In order to keep the observations coming, we’re adding a little bit of incentive. Each time you send in an observation…and this means quality and timely observations and photos from the Turnagain Arm area…your name will be entered in a drawing to be held at the end of each month for a $100 gift certificate from the Friends of the CNFAIC. The gift certificate is good for use at any of our sponsors’ businesses. At the end of the forecast year everyone’s name goes back into the hat for the grand prize…an avalanche beacon of your choice.
Today the avalanche danger is MODERATE. While natural avalanches are unlikely today, there is still the potential of a human triggering a large avalanche. Conditions right now may allow a person to recreate on the same slope all day, but the 20th person could trigger the whole thing, erasing the old tracks. The most likely points to trigger an avalanche today will be in shallow areas of the snowpack near rock outcrops or windscoured ridges, as well as in pockets of newly windloaded snow. A person could find sensitive windslabs near the ridgetops that could fail, and then create a much bigger avalanche if propagation leads into the likely trigger points mentioned above.
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).
The avalanche activity has tapered off since the beginning of this weekend. Many folks have been out recreating in steeper terrain over the past few days, with not much being triggered. The exception to this is the report of a skier triggered avalanche that happened late Sunday afternoon on Twin Peaks near Silvertip. The skier that triggered it was the third person down the slope before it released 500ft from the top of the run. It ran around 1000ft, and stepped down to deeper instabilities several times as it fell down the mountain. You can view a picture of this slide here:
Luckily, the rest of the group picked a good safe zone which they were able to watch the action from. Conditions are kind of scary, because with our slopes acting unpredictably, there is a high level of uncertainty regarding whether or not a slope will avalanche while a person is on it. And even once it has been ridden, the same question keeps popping back into the brain. This is not the best time to go huge, especially if you are able to convince yourself that the snowpack is actually stable.
Recent signs of instability in the form of fast and clean Q1 shears on the facets under the TRC have been observed, which are likely not going away any time soon. Our current snowpack is faceted for the long haul, so do not expect any quick changes in stability right now. The reason for keeping the Danger level at MODERATE is that the unpredictable nature of our persistent weak layers has us scratching our heads. We have been seeing a gradual increase in stability, but there still is a lingering thought that any steep slope could let loose while people jump around on it. Trigger spots of potential avalanches may become harder to find over time, but any resulting avalanche from finding them has the potential to go big. Any new snowloads in the future, be it wind-transported or fallen from the sky, could re-energize any of our persistent weak layers as well.
Our recent avalanches have all been failing on buried layers of surface hoar or facets near crusts, or a combination of the two. Digging in shallow snow might allow you to find these potentially deadly weak layers, so if you find them, give them respect and allow yourself the ability to turn around early without needing to commit to a large run. As much fun as a steep, smooth, leeward, and loaded run is, this is not the best time to be jumping up and down on terrain of this kind. And as a precaution, previous tracks do not indicate stability, so do not allow them to seem so.
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 in the Seattle Creek drainage, avalanche released above rider while performing a slope cut.
-Full burial of snowboarder in Palmer Creek drainage near Hope. Rider was fourth person down the slope. Avalanche triggered near a scoured area of rock on top of a convex rollover; slab failed on facets underneath a crust.
-Skier remotely triggered a medium sized avalanche, approx. 300 feet wide, on east face of Sunnyside near snowmachine uptrack. Fracture propagated uphill.
-Large avalanche on Widowmaker, Seattle Ridge. Unknown trigger.
-Small avalanche on west face of Lips, started near rocks at top. Unknown trigger.
-explosive work in upper Girdwood Valley produced limited results.
-Skier triggered avalanche on Twin Peaks near Silvertip. Skier was third person down the slope. Surface propagation 500ft below ridge and progressed into deeper layers of instability as skier watched from safe zone. Slide ran approx. 1000ft.
Encyclopedia of avalanche terms.
Yesterday was quite clear throughout the pass again, and our inversion is still here. Expect temperatures over the next few days become chilly. The radar is showing a small band of precipitation out over Prince William Sound, but it is headed southwest away from us. Do not expect any new snow today. The sub-polar High that has been keeping us cold and dry is showing continued influence on our area, and is forecasted to do so for at least the next five days.
Kevin 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 WED JAN 12 2011
.TODAY…SUNNY. HIGHS IN THE LOWER TEENS TO LOWER 30S…COOLEST
INLAND. NORTHEAST WIND 10 TO 20 MPH EXCEPT NORTH 20 TO 30 MPH NEAR
.TONIGHT…CLEAR. LOWS 5 BELOW TO 15 ABOVE…COOLEST INLAND.
NORTHEAST WIND 5 TO 15 MPH EXCEPT NORTH 15 TO 30 MPH NEAR SEWARD.
.THURSDAY…SUNNY. HIGHS ZERO TO 25 ABOVE…COOLEST INLAND. VARIABLE
WIND 10 MPH EXCEPT NORTH 15 TO 30 MPH NEAR SEWARD.
TEMPERATURE / PRECIPITATION
SEWARD 31 12 20 / 0 0 0
GIRDWOOD 18 3 14 / 0 0 0
WEATHER STATION SUMMARY for Turnagain Pass:
-3800′ Sunburst Wx Station-
recording increasing winds again. Temps yesterday dropped from 32F to 25F. The current temp is 22 with 12-21mph winds out of the northeast.
-2600′ Seattle Ridge Wx Station-
recording increasing winds again. Temps yesterday dropped from 35F to 25F. The current temp is 24F with 11-17mph winds.
-1800′ Center Ridge Wx Station-
recorded no new snow the last 7 days. Temps within the last 24 hrs dropped from 34F to 22F. The current temp is 22F with a total snowpack depth of 66 inches (1 inch of settlement in the last 24 hours).