Good morning backcountry travelers this is Jon Gellings with the Chugach National Forest Avalanche Information Center on Thursday, January 6th 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).
We are almost 24hrs out of the storm, however give this avalanche cycle more time! Since the new snow fell on such an array of persistent instabilities, the snowpack will likely need more time than the regular 24hr rule-of-thumb.
Today the avalanche hazard is CONSIDERABLE. Large Human triggered avalanches are likely on steep, unsupported and windloaded terrain in upper elevations. At lower elevations, the stability is showing decreased energy, but is still MODERATE due to poor structure and lack of completed bonding processes and due to the possibility that debris from upper elevations could make it to the lower elevations. There are still dangerous avalanche conditions in many areas, and very large human triggered avalanches are likely in isolated areas.
We are dealing with an instability that is still fairly dangerous. This natural avalanche that broke on Sunburst indicates that there was too much stress due to natural processes. In similar areas that have not slid (such as the slope on the left AKA Hoodoo), the stress levels could be teetering on the brink of failure, something which a skier or snowmachiner could definitely push toward the breaking point. AnCNFAIC Staff large avalanche was observed across the valley on Seattle Ridge, which has a picture in the photo gallery. There were also many small and medium sized avalanches (all naturals) that have broke over the past 2-3 days, and may have reloaded to a dangerous extent again.
Yesterday we dug six Extended Column Tests at 1800ft on a 35deg rollover on a SW aspect, hoping to see some great propagation, but they all yielded results inconsistent with these thoughts. All six broke on both the New Year Crust (NYC) and on the Thanksgiving Rain Crust (TRC) with low energy (Q3) and moderate to high strength (ECT 10-30). 2000ft above this spot was where the large avalanche pictured above broke out, so you can see the importance of getting information about the slope you want to travel on.
To tie it all back together, many natural avalanches have just occurred on steep slopes, while some have not. The slopes that have not avalanched will likely be reactive to additional weight in the form of recreationists, so do not be surprised if an avalanche gets triggered by somebody venturing into CONSIDERABLE danger terrain today. Be aware of your surroundings and have a safe and fun day. There is plenty of low angle terrain and new snow to go around, so please do not rush back into committing terrain. Lets give the mountains some more time to adjust to their new covers.
Check out an encyclopedia of terms here: www.fsavalanche.org/Encyclopedia.aspx
Skies are currently clear in Girdwood as of 6:30 this morning, with radar images clear and satellite images currently clear as well. There is anCNFAIC Staff storm on its way (970mb Low pressure system) that could reach us in a few days, although NWS is predicting it will head North toward the Bering Strait and weaken substantially. Temperatures are continuing their cooling trend, and winds are predicted to stay fairly light as well. The snow loading processes have stopped in most areas, but there could be a few straggling slopes that receive some additional wind transport in extreme terrain.
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 THU JAN 6 2011
…STRONG WIND NEAR WHITTIER THROUGH FRIDAY AFTERNOON..
.TODAY…PARTLY CLOUDY IN THE MORNING THEN BECOMING MOSTLY SUNNY.
HIGHS IN THE LOWER 20S TO LOWER 30S. LIGHT WINDS INLAND. NEAR
SEWARD…NORTH WIND INCREASING TO 25 TO 40 MPH. NEAR
WHITTIER…SOUTHWEST WIND 30 TO 45 MPH WITH GUSTS TO 65 MPH.
.TONIGHT…MOSTLY CLEAR. LOWS 5 TO 15 ABOVE EXCEPT IN THE UPPER 20S
NEAR SEWARD AND WHITTIER. LIGHT WINDS INLAND. NEAR SEWARD…NORTH
WIND TO 25 TO 40 MPH. NEAR WHITTIER…SOUTHWEST WIND 30 TO 45 MPH
WITH GUSTS TO 60 MPH.
.FRIDAY…MOSTLY SUNNY. HIGHS IN THE MID TEENS TO LOWER 30S…
COOLEST INLAND. LIGHT WINDS INLAND. NEAR SEWARD…NORTH WIND TO 25 TO
40 MPH. NEAR WHITTIER…SOUTHWEST WIND 25 TO 40 MPH WITH GUSTS TO 50
TEMPERATURE / PRECIPITATION
SEWARD 36 23 33 / 0 0 0
GIRDWOOD 25 13 20 / 0 0 0
WEATHER STATION SUMMARY for Turnagain Pass:
-3800′ Sunburst Wx Station-
recorded wind speeds yesterday up to 43mph, and temps cooling from 23F to 21F. The current temp is 20F with 6-9mph winds out of the northwest.
-2600′ Seattle Ridge Wx Station-
stopped recording winds on 1/2/11, while temps cooled from 26F to 21F yesterday. The current temp is 20F with 98% relative humidity.
-1800′ Center Ridge Wx Station-
recorded 2″ new snow in the past 24hrs, with storm totals looking like 23″ new snow and 2.5″ SWE. Temps yesterday dropped from 30F to 23F. The current temp is 22F with a total snowpack depth of 74 inches.