Good morning backcountry travelers this is Jon Gellings with the Chugach National Forest Avalanche Information Center on Wednesday, December 22nd 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 is LOW, with pockets of MODERATE. Natural avalanches and human triggered avalanches are unlikely overall, while small human triggered avalanches are still possible in steep upper elevation windloaded terrain, and on mountains near large waterways, such as Turnagain Arm, Portage Lake, and Prince William Sound. We have not been seeing much in terms of reactive windslabs on inland, lower elevation mountains, but they may still linger in remote and highly exposed terrain.
Our snowpack is currently showing good stability overall, which is evidenced by ski and snowmachine tracked mountains with no avalanche activity observed. The snow above and around the Thanksgiving Rain Crust is anCNFAIC Staff story, and is growing weaker and weaker over time. We found an anomaly to this faceting process yesterday. We were at a previously windloaded slope on the north side of Tincan, where the TRC was located 4.5 ft deep. Here, the crust was too deep to allow the snow grains a chance at weakening significantly. In most CNFAIC Staff areas, its strength has been deteriorating over the past month, while its energy has stayed fairly low (Q3).
There is fortunately no bed surface for the facets underneath the crust to slide on and produce an avalanche, and there is no cohesive slab (in most areas) stressing these weakening snow grains, which could cause avalanches above the raincrust. Once we get this cohesive slab, which will happen when we get either a substantial amount of new snow or gale-force winds for an undeterminable amount of time, avalanches will probably begin to fail naturally.
We have been hearing reports about a few human triggered wind slabs over the past few weeks, with our most recent one being from three days ago on Pastoral Peak. The variables between most avalanches have been inconsistent, but do follow one same general situation: steep, wind loaded slopes in upper elevation areas with pockets of buried surface hoar and crusts.
Make sure you assess the snowpack for instabilities before you ride any terrain that fits this bill, because those are the places where human triggered avalanches are possible today. We were unable to definitely find the buried surface hoar yesterday, so keep in mind that it is located in some spots and not in CNFAIC Staffs. Follow protocols on safe traveling techniques while in avalanche terrain, and make sure you are prepared for the possibility of someone in your group triggering or getting caught in an avalanche.
Check out an encyclopedia of terms here: www.fsavalanche.org/Encyclopedia.aspx
An inversion is still blanketing our advisory area, with temperatures ranging from 2F at sea level and the Center Ridge weather station, and 14F being recorded at Sunburst weather station. Winds have continually been lower than forecasted throughout Turnagain Pass, so no big changes on that front. The radar is currently showing no precipitation anywhere near our area, and satellite images suggest that our area will be clear of thick clouds for the day. There will be no new snow for the next several days according to the National Weather Service.
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 WED DEC 22 2010
…STRONG WIND THROUGH THURSDAY AFTERNOON NEAR SEWARD AND WHITTIER…
.TODAY…SUNNY. HIGHS ZERO TO 10 ABOVE EXCEPT IN THE LOWER TO MID
20S NEAR SEWARD AND WHITTIER. NORTH WIND 25 TO 40 MPH NEAR SEWARD.
WEST WIND 35 TO 60 MPH NEAR WHITTIER. ELSEWHERE…NORTH TO WEST
WIND INCREASING TO 5 TO 20 MPH.
.TONIGHT…CLEAR. LOWS 10 BELOW TO 5 ABOVE EXCEPT AROUND 15 NEAR
SEWARD AND WHITTIER. NORTH WIND 30 TO 45 MPH NEAR SEWARD. WEST
WIND 40 TO 65 MPH NEAR WHITTIER. ELSEWHERE…NORTH TO WEST WIND
5 TO 20 MPH.
.THURSDAY…SUNNY. HIGHS ZERO TO 10 ABOVE EXCEPT IN THE LOWER 20S
NEAR SEWARD AND WHITTIER. NORTH WIND 30 TO 45 MPH NEAR SEWARD.
WEST WIND 40 TO 65 MPH NEAR WHITTIER. ELSEWHERE…NORTH TO WEST
WIND 5 TO 20 MPH.
TEMPERATURE / PRECIPITATION
SEWARD 20 15 19 / 0 0 0
GIRDWOOD 8 4 7 / 0 0 0
WEATHER STATION SUMMARY for Turnagain Pass:
-3800′ Sunburst Wx Station-
recorded breezy northeast winds yesterday averaging 10-17mph and temps ranging from 13F to 19F. The current temp is 14F with 7mph winds out of the west.
-2600′ Seattle Ridge Wx Station-
recorded mostly light and variable winds yesterday averaging 2-6mph. Temps ranged from 6F to 12F during the day yesterday. The current temp is 9F with light 7 mph winds out of the north.
-1800′ Center Ridge Wx Station-
recorded no new snow since Monday’s 1″. Temps yesterday cooled off from 17F to 7F. The current temp is 2F with a total snowpack depth of 50-51 inches.