Good morning backcountry travelers this is Jon Gellings with the Chugach National Forest Avalanche Information Center on Tuesday, January 11th 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, with pockets of CONSIDERABLE. While natural avalanches are unlikely today, human triggered avalanches still have the potential to go big. The conditions right now may allow you to play 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. The pockets of increased instability are in these newly windloaded areas, where a person could find sensitive windslabs 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).
Since this past weekend, the avalanche activity has tapered off. Many folks have been out recreating in steeper terrain over the past few days, with not much being triggered. However, we just received anCNFAIC Staff 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. Luckily, the group picked a good safe zone which they were able to watch the action from. As Lisa calls it a “scary Moderate”, I have to agree. With slopes acting unpredictably, there is a high level of uncertainty regarding whether or not a slope can/will avalanche while a person is on it. Here is a picture of the slide taken this morning at 10:30:
We are still finding signs of instability in the form of fast and clean Q1 shears on the facets under the TRC, as well as reports of whoomphing in some areas. Our current snowpack has many problems, and is acting with opposing tendencies. It can be really nice to you for a large portion of the ride, but then get angry with you and avalanche big at anytime. The reason for this is the unpredictable nature of our persistent weak layers. We have been seeing a gradual increase in stability, but you will not find me out on anything steep for the time being. 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 could re-energize any of our persistent weak layers as well, so increasingly pay attention if wind speeds stay increased and start loading leeward slopes again.
All of our recent avalanches failed on buried surface hoar or facets near a crust or both. If you dig around in the snow and find any of these potentially deadly weak layers, give them respect and allow yourself the ability to turn around early without the need 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, with an inversion very noticeable. The new winds have mixed up the air throughout Turnagain Pass, so the inversion has likely been corrected in this area. Expect similar temperatures today from yesterday CNFAIC Staffwise. The radar and model images are clear, so do not expect any new snow today.
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 TUE JAN 11 2011
.TODAY…SUNNY. HIGHS IN THE MID 20S TO MID 30S. NORTHEAST WIND
15 MPH EXCEPT NORTH 20 TO 30 MPH NEAR SEWARD.
.TONIGHT…MOSTLY CLEAR. LOWS ZERO TO 25 ABOVE…COOLEST INLAND.
NORTH WIND 15 MPH EXCEPT NORTH 30 TO 40 MPH NEAR SEWARD.
.WEDNESDAY…SUNNY. HIGHS 10 TO 25 ABOVE…COOLEST INLAND. NORTHEAST
WIND 15 MPH EXCEPT NORTH 25 TO 40 MPH NEAR SEWARD.
TEMPERATURE / PRECIPITATION
SEWARD 33 18 24 / 0 0 0
GIRDWOOD 26 7 14 / 0 0 0
WEATHER STATION SUMMARY for Turnagain Pass:
-3800′ Sunburst Wx Station-
recorded a spike in winds up to 38mph a few hours ago. Temps yesterday ranged from 27F to 34F. The current temp is 29F with 12-21mph winds out of the east.
-2600′ Seattle Ridge Wx Station-
also recorded a spike in winds up to 28mph last night. Temps yesterday ranged from 26F to 32F. The current temp is 31F with 14-22mph winds.
-1800′ Center Ridge Wx Station-
recorded no new snow the last 6 days. Temps within the last 24 hrs ranged from 20F to 34F. The current temp is 34F with a total snowpack depth of 67 inches (1 inch of settlement in the last 24 hours).