Turnagain Pass

Good morning backcountry travelers this is Jon Gellings with the Chugach National Forest Avalanche Information Center on Tuesday, December 21st 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).

BOTTOM LINE

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. We have not been seeing much in terms of reactive windslabs, but they may still linger in highly exposed terrain.

AVALANCHE DISCUSSION

Our snowpack is currently showing good stability overall, while the snow above and around the Thanksgiving Rain Crust is growing weaker and weaker. Since it has been in the snowpack for the past month, its strength has been deteriorating, while its energy has stayed fairly low. There is fortunately no bed surface for the facets underneath the crust to fail on and produce an avalanche, and there is no cohesive slab (in most areas) weighing down on top of the snowpack, 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 two 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. 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 an avalanche.

Check out an encyclopedia of terms here: www.fsavalanche.org/Encyclopedia.aspx

WEATHER ROUNDUP

Our inversion has returned, with temperatures at the mountain tops being around 10F, while sea-level temperatures are around 0F. Winds have been fairly benign, and should continue to do so for a few more days, according to weather models. The radar is currently showing scattered pockets of precipitation in Prince William Sound and the Gulf of Alaska. There is not a lot of moisture associated with this wave, so look for the possibility of small amounts of snow in our area.

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-

INCLUDING…WHITTIER…SEWARD…GIRDWOOD…MOOSE PASS

500 AM AKST TUE DEC 21 2010

…STRONG WIND TONIGHT THROUGH THURSDAY NEAR WHITTIER….

.TODAY…MOSTLY CLOUDY WITH A CHANCE OF SNOW. HIGHS 10 TO 25

ABOVE…COOLEST INLAND. WEST WIND 20 TO 35 MPH NEAR WHITTIER. NORTH

25 TO 35 MPH NEAR SEWARD. VARIABLE WIND 10 MPH ELSEWHERE.

.TONIGHT…PARTLY CLOUDY. LOWS ZERO TO 20 ABOVE…COOLEST INLAND.

WEST WIND 30 TO 45 MPH NEAR WHITTIER. NORTH 25 TO 35 MPH NEAR SEWARD.

VARIABLE WIND 10 MPH ELSEWHERE.

.WEDNESDAY…MOSTLY SUNNY. HIGHS 10 TO 25 ABOVE…COOLEST INLAND.

WEST WIND 30 TO 45 MPH NEAR WHITTIER. NORTH 25 TO 35 MPH NEAR SEWARD.

NORTHWEST WIND 10 TO 15 MPH ELSEWHERE.

TEMPERATURE / PRECIPITATION

SEWARD 24 18 23 / 40 0 0

GIRDWOOD 15 6 13 / 20 0 0

WEATHER STATION SUMMARY for Turnagain Pass:

-3800′ Sunburst Wx Station-

recorded light west winds yesterday averaging 2-9mph and temps ranging from 4F to 12F. The current temp is 11F with 6mph winds out of the east.

-2600′ Seattle Ridge Wx Station-

recorded mostly light and variable winds yesterday averaging 2-8mph. Temps ranged from 6F to 12F during the day yesterday. The current temp is 9F with light winds out of the northeast.

-1800′ Center Ridge Wx Station-

recorded no new snow since yesterday. Temps yesterday cooled off from 17F to 7F. The current temp is 9F with a total snowpack depth of 50 inches.